v school for young scientists magnetic resonance and magnetic...
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Institute of Chemical Kinetics and Combustion
International Tomography Center
Novosibirsk State University
Free University of Berlin
Max Planck Institute for Biophysical Chemistry, Göttingen
V School for young scientists
Magnetic Resonance and Magnetic
Phenomena in Chemical and Biological
Physics
Book of abstracts
St. Petersburg, Russia
2018
Organizers
Sponsors
Voevodsky Institute of Chemical Kinetics and
Combustion, Novosibirsk
Free University of Berlin
Max Planck Institute for Biophysical Chemistry,
Göttingen
Novosibirsk State University
International Tomography Cente, Novosibirsk
Organizing Committee
Chair — Leonid Kiluk
Vice-chair — Konstantin Ivanov
Nikolay Isaev
Egor Nasibulov
Alexander Popov
Program Committee
Chair — Victor Bagryansky
Vice-chair — Konstantin Ivanov
Yuri Molin
Yuri Tsvetkov
Program
September 15: Arrival
19.00 — 23.00 Welcome party
September 16: Theoretical framework for magnetic resonance
9.00 Plenary talk: Quantum Mechanics of NMR and. Ivanov
11.00 Coffee break
11.30 Lecture: Electron and nuclear spin dynamics. Maeda
13.00 Lecture: Basic pulse experiments in magnetic resonance. Kulik
14.00 — 15.00 Lunch
15.00 Lecture: Relaxation in magnetic resonance. Ivanov
16.30 Lecture: Product operator formalism. Griesinger
18.00 Coffee break
18.30 Tutorial: Product operator formalism. Yulikov
September 17: NMR
9.00 Plenary talk: Modern methods in bio-NMR. Griesinger
11.00 Coffee break
11.30 Lecture: NMR interactions. Ivanov
13.00 Lecture: Spin interaction tensors. Ivanov
14.00 — 15.00 Lunch
15.00 Lecture: NMR pulse sequences. Griesinger
16.30 Tutorial: NMR structure determination — a practical guide. Tietze
18.00 Coffee break
18.30 Flash talk session
September 18: EPR
9.00 Plenary talk: Pulsed dipolar EPR spectroscopy. Yulikov
11.00 Coffee break
11.30 Lecture: EPR interactions. Kulik
13.00 Lecture: Relaxation in EPR. Kulik
14.00 — 15.00 Lunch
15.00 Lecture: Pulsed EPR instrumentation. Yulikov
16.30 Tutorials: Pulse EPR simulations with EasySpin/SPIDYAN,
DeerAnalysis/OvertoneAnalysis, MMM (Multiscale Molecular Modeling)
highlights. Yulikov
18.00 Coffee break
18.30 Flash talk session
September 19: Spins of electrons and nuclei
9.00 Plenary talk: Dynamic Nuclear Polarization. Gutmann
11.00 Coffee break
11.30 Lecture: Spin hyperpolarization. Gutmann
12.30 Lecture: Hyperfine interactions in solid state EPR. Kulik
14.00 — 15.00 Lunch
15.00 Lecture: Magnetoreception and magnetic field effects. Maeda
16.30 Lecture: Chemically induced electron spin polarization. Maeda
18.00 Coffee break
18.30 Tutorials: Hyperfine spectroscopy. Yulikov
20.00 Poster session
September 20: NMR and EPR in action
9.00 Plenary talk: NMR-based studies of biomolecules. Tietze
11.00 Coffee break
11.30 Lecture: Chemically induced nuclear spin polarization. Yurkovskaya
13.00 Lecture: Site-directed spin labeling in EPR. Yulikov
14.00 — 15.00 Lunch
15.00 Lecture: Recent highlights in magnetic resonance. Gutmann
16.30 Lecture: Recent highlights in spin chemistry. Maeda
18.00 Coffee break
18.30 Closing of the School
Departure
POSTERS
Poster 1
Trichogin-induced stearic acid re-arrangement in the membrane
Ekaterina Afanasyeva, [email protected]
Voevodsky Institute of Chemical Kinetics and Combustion, Institutskaya-3, Novosibirsk,
630090, Russia, and
Novosibirsk State University, Pirogova-2, Novosibirsk, 630090, Russia
PhD Victoria Syryamina, Prof. Sergei Dzuba
Trichogin GA IV (Tri) is short 10-mer peptides, isolated from fungi Trichoderma, that
manifest a biological activity against line of pathogens. One of the mechanisms of membrane
perturbation by peptides is based on the peptide influence on the lipid chain ordering. Due to different
mismatch conditions, peptides could change the membrane thickness and curvature, changes the
bilayer rigidity.
In this work we compare peptide self-association in the membrane and peptide influence on
the fatty acid distribution in the lateral membrane by antimicrobial peptide Trichogin GA IV and its
non toxic analog [Leu4]trichogin. The combination of EPR techniques – Continuous Wave EPR (CW),
Pulse-Electron Double Resonance (PELDOR or DEER), Electron Spin Echo Envelop Modulation
(ESEEM) and 2-pulse echo decay due to dipolar coupling (instantaneous diffusion) – extracts the
information about peptide-peptide and peptide-lipid interactions.
Recently we found the Alamethicin influence on the fatty acid distribution that may compete
with stepwise peptide channel formation [1]. Fatty acids are building blocks of lipid chains and also
facilitate peptide/protein ―anchoring‖ in the membrane. The anchor role is relevant for bimolecular
functioning. The modification of fatty acids distribution in the membrane plane reflects on the
membrane functions.
In this work we compare two-side Trichogin effect on the lipid bilayer structure. The first
one is the peptide self-assembling process in the membrane interior. The second is changing of stearic
acid distribution in the membrane plane at the peptide action. Both process have a triggering-like
dependence for active trichogin and activates above critical P/L* = 2/200 – 4/200. Below P/L* peptide
molecules have a planar monomeric state in the membrane plane, stearic acid forms local clusters, no
interaction between peptides and stearic acids is observed. Above critical P/L ratio, Trichogin
molecules tend to form dimmers. Dimers, probably, have tilted state in the membrane plane.
Simultaneously, above critical P/L the increasing of stearic acid clusters is observed, that is
accompanied by mutual attraction between stearic acids and peptides dimers. Probably, Trichogin
dimers disrupt the lipid chain packing around itself and work as attractors for stearic acids. Stearic
acids with less polar head in compare with lipids could reduce the discrepancy of bilayer structure near
peptide dimers disturbances. For non toxic trichogin such effects aren‘t observed.
[1] Afanasyeva, E. F., Syryamina, V. N., & Dzuba, S. A. (2017). The Journal of chemical physics, 146(1),
011103.
Poster 2
Figure 1. 1H NMR spectra of cobalt (II)
tris-imidazole-oximate.
A new single molecule magnet based on cobalt(II) tris-imidazole-oximate: NMR and magnetomery studies
Dmitry Yu. Aleshin1, 2
1Dmitry Mendeleev University of Chemical Technology of Russia. 125047, Russia,
Moscow, Miusskaya sq. 9
2A.N. Nesmeyanov Institute of Organoelement Compounds. 119991, Russia, Moscow,
Vavilova st. 28
Alexander A. Pavlov, PhD
A single molecule magnet (SMM) is a compound exhibiting the property of a permanent
magnet on the molecular level. The SMM in an external magnetic field acquires the magnetization and
keep it for a time due to the presence of the magnetization reversal energy barrier U. This barrier is
caused by a negative zero field splitting energy D, resulting in a direct transition from Ms = -S to Ms =
+ S is become forbidden by the selection rules.
Trigonal prismatic geometry of cobalt(II) tris-
imidazole-oximate (Fig. 1) leads to a strong spin-orbit
coupling, which is the prerequisite of slow
magnetization relaxation of the SMM [1].
Magnetometry allows to obtain an isotropic value
of the magnetic susceptibility tensor (χiso), while
anisotropy of this tensor can be obtained by NMR
spectroscopy, although this method is rarely used for
paramagnetic compounds due to fast nuclear relaxation.
The χ-tensor obtained by the method of magnetometry
and NMR allows to estimate the ligand crystal field
parameters and , using the following spin Hamiltonian, which takes into account the spin-orbit
coupling.
Using this approach, the energies of the Kramers doublets for the investigated complex are
calculated and taken the following values 0, 154, 402, 583, 2344, 2370 cm-1
. The energy of the second
doublet relative to the first one can be considered as the value of U (154 cm-1
). According to the
magnetometry data, the value of the effective magnetization reversal energy barrier is lower (101 and
130 cm-1
in the absence and presence of an external magnetic field, respectively). This difference is
due to the presence of the alternative Raman relaxation mechanism.
The study was supported by the Council of the President of the Russian Federation (Project MK-
2179.2017.3).
[1] Valentin V. Novikov, Alexander A. Pavlov, Yulia V. Nelyubina, Marie-Emmanuele Boulon., Oleg A.
Varzatskii, Yan Z. Voloshin and Richard E.P.Winpenny, J. Am. Chem. Soc., 2015, 137 (31),pp 9792-9795
Poster 3
EPR study of copper exchanged species in mordenite channels
Dmitrii Bogdanov1, [email protected]
1Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, Russia
199034
Sc. supervisor: Dr. Marina Shelyapina
Copper-exchanged zeolites are promising heterogeneous catalysts for the decomposition of
nitrogen oxides (de-NOx catalysts), the selective hydroxylation of methane to methanol and other
industrial processes [1]. These catalytic properties are governed by both content of copper, which can
be localized in various positions of the coordination lattice with different local symmetry, and its
valence state. While parameters mentioned above are determined by the preparation method. At the
current time a large quantity of studies of location and coordination of copper cations in zeolites has
been performed. However, often these studies used only low copper content samples, despite the fact
that mainly high content zeolites produced best catalytic results. Copper mordenite (CuMOR) is
among the best copper zeolite catalysts [2], and as such, more intense study of high content samples is
required for more fundamental understanding.
The aim of this work is to study the location of Cu2+
cations and their coordination in the
high copper containing mordenite samples, prepared by conventional and microwave assisted methods
(for more details on preparation method see [3]). EPR spectroscopy, as the best method to detect
presence of Cu2+
ions in the sample and identify nearest environment and its local symmetry of
paramagnetic ions, was used in the work. According to EPR study there are at least two different
paramagnetic centers of Cu2+
that can be attributed to [Cu(H2O)n]2+
complexes. Upon the sample
dehydration one observe the general decrease of EPR signal intensity that can be explained as follows:
Cu2+
ions from [Cu(H2O)n]2+
species loosing water approach to the wall of zeolite channel and form
virtual bonds with charge transfer from framework oxygens to Cu2+
. This charge transfer process is
reversible and rehydration of the sample leads to the recovering of Cu2+
ions coordination.
Acknowledgements:
The structural, elemental and EPR analyses were carried out at the Research Park of Saint
Petersburg State University: Centre for X-ray Diffraction Studies, Interdisciplinary Resource Centre
for Nanotechnology, Centre for Physical Methods of Surface Investigation, and Centre for Magnetic
Resonance.
References:
[1] Vanelderen, P. , Vancauwenbergh, J. , Tsai, M. , Hadt, R. G., Solomon, E. I., Schoonheydt, R. A. and
Sels, B. F. ChemPhysChem, 2014, 15, 91
[2] E. M. Alayon, M. Nachtegaal, M. Ranocchiari, J. A. van Bokhoven, Chem. Commun. 2012, 48, 404
[3] Zhukov Y.M., Efimov A. Yu., Shelyapina M.G., Petranovskii V., Zhizhin E.V., Burovikhina A.,
Zvereva I.A. MicropMesoporMat, 2016, 224, 416
Poster 4
Solid-state investigation of zeolite acidity using trimethylphosphine oxide probe molecules
Carlos Bornes1, [email protected]
1CICECO − Aveiro Institute of Materials, Departmento de Química, Universidade de
Aveiro, 3810-193 Aveiro, Portugal
Luís Mafra1, Ph.D & João Rocha
1, Ph.D
Over the past decades, the acidic properties of zeolites were extensively investigated and found
major industrial applications, namely as catalysts in petrochemical industry processes. Several
spectroscopic and analytical techniques were employed to investigate these properties, and most
contributions found in the literature are controversial. Solid-state NMR is among the most used
spectroscopic techniques to investigate zeolite acidity. Combined with the adsorption of molecular
probes, accurate information about the type, strength and amount of acid sites can be obtained through
solid-state NMR. Trimethylphosphine oxide (TMPO) has been used in the last few years to investigate
both solid and liquid acids. The intrinsic properties of the NMR active nucleus (31
P), such as the broad
chemical shift range, high natural abundance, and its smaller size, compared with other widely used
phosphorous-containing probes, makes TMPO a very attractive probe to investigate zeolites acidity.
This project aims at performing a comprehensive study of acid sites in several related zeolites,
prepared with subtle modifications to obtain materials with distinct acidic properties, namely the type,
strength, amount of both Lewis and Brønsted acid sites. Site-selective information can be obtained
combining multinuclear 1D and 2D solid-state NMR experiments with computational calculations.
Preliminary results showed that TMPO is a powerful probe to obtain structural information on the pore
surface, allowing not only the differentiation between Brønsted and Lewis acidity but also accessing
the acid strength of these sites. We anticipate using 1D and 2D homonuclear and heteronuclear
correlation techniques, such as 1H-X HETCOR MAS NMR (X=
29Si,
31P,
17O), DQ-SQ correlation
spectroscopy and double/triple resonance recoupling methods (e.g., RESPDOR, REAPDOR,
TRAPDOR) using conventional and DNP surface-enhanced SSNMR methods.
Poster 5
MRI study of the influence of superparamagnetic iron oxide
nanoparticles (SPIONs) on the relaxation properties of water in
agarose matrix
Aleksandra Efimova1, [email protected]
1Faculty of Physics, St. Petersburg State University, Russian Federation
Scientific supervisor: Ass. Prof. Dr. Tolstoy P.M., Department of Physical Organic
Chemistry Institute of Chemistry, Saint-Petersburg State University
The method of magnetic resonance imaging (MRI) has found wide application in the field of
medical diagnostics and monitoring, as well as for studying various characteristics of biological
tissues. For effective diagnostics, paramagnetic substances are often used as contrast agents, providing
significant enhancement of relaxation contrast [1].
In our work, as a contrast agent we propose to use superparamagnetic iron oxide nanoparticles
(SPIONs) entrapped in cellulose microbeads (CM) or covered by a protective polymeric layer of
chitosan in agarose matrix. The cellulose can be converted into porous beads (spherocells) with high
specific internal surface. Porous spherocells can uptake large amount of magnetite and have higher
relaxivity than usual aqueous suspensions of SPIONs. CM/SPION system potentially may serve as a
model contrast agent for MRI study of large eukaryotic cells such as macrophages and mesenchymal
stem cells [2].
The goal of our work is to study the influence of SPIONs on the proton relaxation
characteristics of water in agarose matrix.
Figure 1. FLASH-images of five layers:agarose (1), cellulose microbeads (2), SPIONs
entrapped in CM (3), SPIONs covered with chitosan (67.5 μmol/L) (4) and SPIONs covered with
chitosan (6.75 μmol/L) (5) (slice thickness is 0.5 mm, the size of each image is 12х12 mm).
MR images of gel samples demonstrate the contrast efficiency of magnetic cellulose microbeads
as negative contrast agents.
Magnetic microbeads provide strong shortage of transverse relaxation times T2 of water protons
due to high content of magnetic particles and water interchange in perturbed magnetic field
around iron oxide nanocrystals. Each of the particles create large black spot acting as a negative
contrast agent. Such black spots are much bigger than the size of each CM/SPION systems.
Similar effects on T2 were achieved in the samples with high concentration of chitosan-covered
SPIONs.
Acknowledgments We are grateful to B.P. Nikolaev, L.Y. Yakovleva, I.N. Voevodina for preparation of
magnetic dispersions, cellulose microspheres and useful discussions, A.S. Mazur for help in
conducting the MRI experiments. MRI measurements were performed at Center for Magnetic
Resonance of Saint Petersburg State University Research Park. [1] M. Shevtsov, B. Nikolaev, Y. Marchenko, L. Yakovleva, N. Skvortsov, A. Mazur, P. Tolstoy, V. Ryzhov,
G. Multhoff, Int. J. Nanomed., 2018, 13, 1471–1482
[2] C.V. Bowen, X. Zhang, G. Saab, P.J. Gareau, B.K. Rutt, Magn. Reson. Med., 2002, 48, 52–61
Poster 6
NMR spectroscopy of blood serum and brain tissue of NOD SCID
mice with type 1 diabetes mellitus
Anastasia V. Glinskikh1,2,3
1Institute of Cytology and Genetics, Academician Lavrentyev Ave. 10, 630090,
Novosibirsk, Russia
2Novosibirsk State University, Pirogova str. 2, 630090, Novosibirsk, Russia
3 International Tomography Center, Institutskaya str. 3a, 630090, Novosibirsk, Russia
Andrey E. Akulov PhD in Biology
The method of NMR spectroscopy is widely used in studies of living systems in norm and
pathology. Progress in studying "metabolic diseases" relates to the results of "omic" sciences. Diabetes
mellitus type 1 (T1DM) belongs to the group of metabolic diseases, which violate the carbohydrate
metabolism. In this work, the study of the effect of type 1 diabetes mellitus on brain tissue was
performed on laboratory mice of NOD SCID line. While laboratory mice are the most popular object
in biomedical research, there is a lack of studies on the metabolic profile of biological tissues of
laboratory mice in the model of T1DM. In this regard, it seems relevant to use one of the main
methods of metabolomics - NMR spectroscopy.
Previous studies showed significant differences in concentrations of metabolites in the blood
of the control / diabetes groups. To assess the effect of blood on the metabolism of the brain tissues an
additional study was performed on two groups: brain tissue in the native state and after perfusion
(removal of blood from the tissue). As a result, we found that the metabolic profiles of the brain with
the presence of blood and in its absence do not differ between each other, which allowed conducting a
study of native samples of the brain tissue of the control / diabetes groups.
To study the effect of type 1 diabetes mellitus, the 32 mice of NOD SCID line were divided
by sex and further into 2 groups: control / diabetes. By the results of NMR spectroscopy of brain
tissue, 35 metabolites were identified. Moreover, in female NOD SCID mice with type 1 diabetes
mellitus, a significant change in the concentration of glutamine and lactate is observed. The results for
males show a significant change in the concentration of glutamine, tyrosine, lactate and benzaldehyde.
The study provides new knowledge about the metabolism of mouse tissues under conditions
of T1DM and demonstrates the effectiveness of NMR spectroscopy for the further development of
metabolomics. The work was supported by the project of SB RAS Program No. 0324-2018-0028.
Poster 7
High-Frequency Electron Spin Resonance Spectroscopy of
High-Spin CoII
Ions in Cobalt-Ferrocene Dimers
Jakub Hrubý1, [email protected]
1Central European Institute of Technology, Brno University of Technology, Czech
Republic
Ing. Petr Neugebauer, Ph.D.
A novel approach to electronics is based on two novel disciplines; spin electronics and
molecular electronics. A fundamental connection between these two fields can be established
using molecular magnetic materials, in particular, single-molecule magnets (SMMs) [1].
Herein, we report a spectroscopic investigation of selected cobalt-based SMMs by high-
frequency electron spin resonance (HFESR).
Bulk properties of cobalt-ferrocene dimers (CFDs) with linear chemical formula:
[X2Co(P(C6H5)2C5H4)2Fe, where X = Br, Cl, and (P(C6H5)2C5H4)2Fe = dppf] were
investigated by HFESR and allowed us to determine the spin Hamiltonian parameters, namely
the g-tensor and zero-field splitting (ZFS) terms representing bulk magnetic properties. ZFS
parameter D is the axial component of magnetic dipole-dipole interaction and E is the
transversal component. CoII
ions are in tetrahedral 3d7 electron configuration in a high-spin
state (S = 3/2). On the contrary, FeII
ions are in the 3d7 low-spin state (S = 0) with no unpaired
electrons, and thus only CoII contributes to overall HF-ESR spectrum. The best fit for
[Co(dppf)Br2] spectrum was found for D = -11.2 cm-1
with E/D = 0.09, and gx = 2.22, gy =
2.22, gz = 2.28. These results are in fair agreement with ab initio quantum chemical
simulations (CASSCF/NEVPT2). The effective energy barrier can be then calculated as:
cm-1
.
Acknowledgments: This research has been financially supported by the Ministry of Education,
Youth and Sports of the Czech Republic under the project CEITEC 2020 (LQ1601).
This work/Part of the work was carried out with the support of CEITEC Nano Research
Infrastructure (ID LM2015041, MEYS CR, 2016–2019), CEITEC Brno University of Technology.
[1] Bogani, L. & Wernsdorfer, W. Molecular spintronics using single-molecule magnets. Nature Materials
7, 179, doi:10.1038/nmat2133 (2008).
Poster 8
Membrane transporter PutP structural change observed by
site–directed spin labeling, D2O ESEEM and cw EPR together
with simulation of PutP conformations and corresponding
distributions of attached spin labels and D2O
Nikolay Isaev1, Nikita Ivanisenko
2,3, Susanne Bracher
4, Heinrich Jung
4, Heinz-Jürgen Steinhoff
5
1Voevodsky Institute of Chemical Kinetics and Combustion SBRAS, Novosibirsk, Russia
2Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia
3Novosibirsk State University, Novosibirsk, Russia
4Department of Biology, Maximilians-University of Munich, Munich, Germany
5Physics Department, University of Osnabrück, Osnabrück, Germany
E-mail: [email protected]
Electron spin echo envelope modulation (ESEEM) is a pulse EPR technique sensitive to the
nearby nuclei in the range of 1nm, which is convenient for protein study. ESEEM was previously used
as a qualitative tool to determine the water environment of spin labels attached to lipids, peptides and
proteins [1]. However numerical calculations of the ESEEM signal from D2O and its comparison to
the experimental data, like in work [2], were rarely done.
In this work we measured 2H ESEEM for 21 different labeling positions in the sodium-proline
transporter PutP in the presence (holo state) and absence (apo state) of substrates. Also we measured
cw EPR at room temperature to determine the label mobility, and at 160K to obtain the hyperfine
splitting, which is sensitive to the polarity of the label environment. We could experimentally observe
differences between the apo and holo states.
To explain the experimental results we made a homology model of PutP using the X-ray
structure of the closest family member sodium-galactose transporter vSGLT in the apo and holo states
and included spin labels into the structures. We hydrated these structures and, using ESEEM
calculation from [2], we determined the ESEEM signal changes for every label position and protein
state. To match experimental and simulated 2H ESEEM signal changes we had to modify the holo state
of vSGLT by according to the structure of the sialic acid/sodium symporter SaiT.
We could obtain a good correlation of experimental and simulated ESEEM signal changes upon
substrates addition. Thus, ESEEM in combination with site-directed spin labeling is suggested as
additional tool to verify models for protein conformational changes.
Acknowledgements
This work was supported by Alexander von Humboldt Foundation. Computational modeling was
funded by the Russian Science Foundation grant 14-44-00011.
[1] Dzuba, S. A., & Marsh, D. (2014). ESEEM of spin labels to study intermolecular interactions, molecular
assembly and conformation. In Electron Paramagnetic Resonance (pp. 102-121).
[2] Milov, A. D., Samoilova, R. I., Shubin, A. A., Grishin, Y. A., & Dzuba, S. A. (2008). ESEEM Measurements
of Local Water Concentration in D 2 O-Containing Spin-Labeled Systems. Applied Magnetic Resonance, 35(1),
73-94.
Poster 9
Formation and redox properties of chelate complexes of
deferasirox with Fe and Cu ions
Lilia Kichigina1,2
, Viktor Timoshnikov1,2
, Nikolay Polyakov1, George
Kontoghiorges3
e-mail: [email protected]
1Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia
2Novosibirsk State University,Novosibirsk, Russia
3Postgraduate Research Institute of Science, Technology, Environment and Medicine,
Limassol, Cyprus
Scientific advisor: Nikolay Polyakov, PhD
Deferasirox is the chelator that is used to treat diseases associated with excess iron in the body,
for example thalassemia [1]. Despite the many benefits of this treatment, such as the oral route of
administration, this chelator has serious side effects that can lead to death. The causes of these effects
are still unknown. Also it is known that this chelator is photostable, but we don‘t known about the
photochemical activity of its chelate complexes with metal ions. Metals are able to change the
absorption spectrum of the complex and affect on the redox properties of the chelator [2].
Thus, in this work we investigated (1) the complexation of deferasirox with iron and copper ions;
(2) the antioxidant properties of deferasirox in the reactions of oxidation of ascorbic acid and
dihydropyridine in the presence of iron and copper ions; (3) the photochemical activity of deferasirox
and its chelate complex with iron ions in the absence and presence of electron donor and acceptor,
namely dihydropyridine and chloranil. The investigations were carried out by means of optical
spectrophotometry, NMR spectroscopy, and CIDNP method in non-aqueous solutions.
As a result of our investigations, the stoichiometry of chelate complexes of deferasierox with iron
and copper ions was calculated. It was shown that deferasirox inhibits the oxidation of the asorbic acid
and dihydropyridine in reactions involving iron and copper ions. Deferasirox and its chelate
complexes with iron ions do not have photochemical activity in the presence as well as in the absence
of donors and acceptors of electron.
The reported research was funded by Russian Foundation for Basic Research, grant №18-34-
00343
[1] Committee for Medicinal Products for Human Use, Assessment report: EXJADE International non-
proprietary name: deferasirox, London, United Kingdom: European Medicines Agency, 2017.
[2] Glebov E. M. et al., Intermediates in photochemistry of Fe (III) complexes with carboxylic acids in
aqueous solutions, Photochemical & Photobiological Sciences, 2011, 10 (3), 425-430.
Poster 10
Solvent and concentration dependence of the hydroxyl 1H
chemicalshift of fluoroalcohols
Yunmi Kim, [email protected]
Department of analytical chemistry, University of Leipzig, Linnéstraße 3, 04103 Leipzig,
Germany.
Supervisors: Dr. Chen Song, M.Sc. Pavlo Bielytski, Prof. Dr. Jörg Matysik
Hexafluoro-isopropanol (HFIP) is most successfully used solvent to enable to dissolve
polymer such as polyester and polyamides and it also stabilizes secondary structure of protein
because of its particular properties modified by fluorination [1]. In this work we measured on 1H chemical shift of hydroxyl group using solution NMR of isopropanol (IP) and trifluoro-
isopropanol (TFIP) and HFIP mixing with three solvents (CDCl3, toluene-d8, DMSO-d6) with
a molar ratio from 0 to 1. With the 1H data, we studied the fluorination effect of this series of
alcohols and solvation effect on hydrogen-bond between alcohols and solvents. The larger 1H
chemical shift value was found in very diluted region 0.2mol% of HFIP in CDCl3and exhibits
a slow increase upon the concentration, indicating the preference of hydrogen bond with the
solvent. The 1H chemical shift in the this very diluted region (0.2mol% of alcohol) in CDCl3
decreased in the order of HFIP, TFIP, and IP, it reveals that the hydrogen bond is much
affected by fluorination. Additionally, the reduction of hydrogen-bonding strength between
fluorinated alcohol molecules compared to IP molecules evidenced by smaller chemical shift
in higher concentrated region was observed in CDCl3 and toluene-d8. But the reduction
tendency was not kept in DMSO-d6. It seems that fluorination effect on conformation of
hydrogen bond and their clusters is influenced by different solvents. Hydroxyl chemical shift
of these three alcohols in DMSO showed the highest value in very diluted region and slow
increasing tendency relative to that in CDCl3 and toluene-d8, besides the case of HFIP showed
the largest chemical shift in DMSO-d6, it is demonstrated that DMSO-d6 is most interactive
solvent with HFIP to form an intermolecular hydrogen bond. This study will assist theoretical
studies towards understanding of the dissolving process of polymers in HFIP and provide
deeper insights into hydrogen-bonding networks of fluoroalcohols upon mixing with
polar/non-polar organic solvents.
References [1] Ignacio Colomer, Anna E. R. Chamberlain, Maxwell B. Haughey and Timothy J. Donohoe,
Hexafluoroisopropanol as a highly versatile solvent, Nature reviews, chemistry vol.1, 0088, (2017)
[2] M. A. Wendt, J. Meiler, F. Weinhold and T. C. Farrar. Solvent and concentration dependence of the
hydroxyl chemical shift of methanol, Molecular phys. (1998), Vol 93, No.1, 145-151
[3]Takehiko Tsukahara, Masayuki Harada, Hiroshi Tomiyasu, and Yasuhisa Ikeda, NMR Studies on Effects
of Temperature, Pressure, and Fluorination on Structures and Dynamics of Alcohols in Liquid and Supercritical
States, J. Phys. Chem. A (2008), 112, 9657-9664
Poster 11
Towards establishing SABRE as a routine high-field NMR
technique
Stephan Knecht1,2
1University Medical Center Freiburg, Freiburg, Germany
2University of Freiburg, Freiburg, Germany
Supervisor: Prof. Dr.Dr.h.c. Jürgen Hennig
The project is concerned with the, parahydrogen based, nuclear spin hyperpolarization method
Signal Amplification By Reversible exchange [1] (SABRE). The goal of the thesis is twofold: firstly,
the development and implementation of a general model to account for both chemical exchange
processes as well as spin dynamics. Secondly, utilization of the model for identification and better
understanding of the factors which make sabre efficient as well as for the development of efficient
transfer schemes at high field. During the project a very general theoretical approach to SABRE base
on stochasitcalLvN equations was implemented and analyzed for SABRE conditions at low and high
magnetic fields [2]. This model was subsequently employed to develop a highly effective
repolarization method utilizing INEPT type pulse sequences at high magnetic fields [3]. Furthermore,
it was found that parahydrogen (which is externally supplied in SABRE experiments and is present in
the solvent before polarization transfer occurs) does not remain in the singlet state but rather
undergoes rapid S-T0 conversion[4]. This conversion was found to be both the source of spontaneous
polarization transfer at high magnetic fields [4] as well as an important factor for the efficiency of
high-field SABRE polarization schemes [5]. This S-T0 mixing occurs in reaction intermediates of the
main SABRE complex which most likely involves binding of the solvent. One of my current research
interests is modelling the processes in such secondary complexes to gain a better understanding of
their role in the SABRE process. We hope that this will not only allow us to improve already existing
transfer schemes but may also lead the way to effective solvent polarization via SABRE.
Acknowledgements: I like to acknowledge the research group of Konstantin Ivanov at the ITC
(Novosibirsk),where I spend 9 months as a visiting scientist, in general and Prof. K. Ivanov, Prof A.
Yurkovskaya and Dr. A. Kiryutin in particular.
[1] Adams, R. W. et al., Science, 2009,323,1708 (DOI: 10.1126/science.1168877)
[2] Knecht et al, RSC Advances 2016, 29 (DOI: 10.1039/C5RA28059A)
[3] Knecht et al, JMR 287,10-14,2018 (DOI: 10.1016/j.jmr.2017.12.010)
[4] Knecht et al, JMR 287,74-81,2018 (DOI:10.1016/j.jmr.2017.12.018)
[5] Knecht et al,arxiv-preprint (arXiv:1802.04471)
Poster 12
The Behavior of Isotropic Bicelles of Various Compositions
EF Kot1,2
, [email protected], S.A. Goncharuk1,2
, A.S. Arseniev1,2
,
K.S. Mineev1,2
1Shemyakin−Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of
Sciences RAS, str. Miklukho-Maklaya 16/10, Moscow 117997, Russian Federation
2Moscow Institute of Physics and Technology, Institutsky per., 9, 141700 Dolgoprudnyi,
Russian Federation
Supervisor: Konstantin S. Mineev1,2
, PhD.
Isotropic bicelles (IsoBs) are a convenient and widely used membrane mimetic in structural
NMR studies of membrane proteins and their transmembrane domains[1]. The great advantage of
IsoBs is the presence of a patch of the planar lipid bilayer together with the small size of particles,
which allows registering the well-resolved spectra of proteins in the membrane-like environment.
Despite the fact that lots of studies utilizing IsoBs were performed, their behavior was not
examined in much detail. There are still doubts regarding the morphology of particles, the existence of
bilayer patch and the degree of lipid/detergent segregation.
Phase transitions are a fundamental property of lipid bilayers. Observation of phase
transitions in bicelles can approve the morphology of the particles. In our work we have developed a
method of detecting lipid phase transitions in IsoBs by 31
P solution NMR and showed their existence
in different bicelle samples.
Proceeding further, we carry out a thorough study of IsoBs of various compositions in
different environment and concentrations. Using 31
P NMR to detect the phase transitions of lipids and
applying the 1H DOSY for comparing the particle size with the ideal bicelle model, we rate the quality
of bicelle formation and the applicability of different bicellar mixtures for structural studies. We show
that the IsoBs indeed contain a patch of lipid bilayer that mimics the membrane environment,
however, not all of the already reported compositions reveal a bicelle-like behaviour [2].
The work is supported by the Russian Science Foundation, grant #14-14-00573.
[1] D. E. Warschawski, A. A. Arnold, M. Beaugrand, A. Gravel, É. Chartrand, и I. Marcotte, «Choosing
membrane mimetics for NMR structural studies of transmembrane proteins», Biochim. Biophys. Acta, т. 1808,
вып. 8, сс. 1957–1974, авг. 2011.
[2] E. F. Kot, S. A. Goncharuk, A. S. Arseniev, и K. S. Mineev, «Phase Transitions in Small Isotropic
Bicelles», Langmuir ACS J. Surf. Colloids, т. 34, rel. 11, сс. 3426–3437, March. 2018.
Poster 13
Spin dynamics in experiments on orthodeuterium induced
polarization of nuclei
Vitaly P. Kozinenko1,2
1International Tomography Center, Institutskaya str. 3a, 630090, Novosibirsk, Russia
2Novosibirsk State University, Pirogova str. 2, 630090, Novosibirsk, Russia
Konstantin L. Ivanov, Doctor of Physico-mathematical sciences;
Alexey S. Kiryutin, Candidate of Chemical Sciences
OrthoDeuterium Induced Polarization (ODIP) is one of the methods of creating
hyperpolarization in nuclear spins systems. The signal amplification in ODIP method occurs due to the
nonequilibrium population of the nuclear spin states in the molecule of ordeutherium. This method can
be used in the study of isotope effects in catalytic hydrogenation reactions. Deuterium nuclei have a
spin equal to 1, hence the spin dynamics is more complex than in the case of protons with spin ½, in
experiments on PHIP (ParaHydrogen Induced Polarization). Therefore, an important step for the
application of ODIP is to carry out the experiments similar to the basic experiments with PHIP.
In this paper, we perform theoretical and experimental study of spin dynamics of ODIP
under experimental conditions of PASADENA [1], ALTADENA [2] and OPSY [3]. Nutation
dependencies (the dependence of the NMR lines intensities on the magnetization rotation angle) for
deuterium polarization and a type of spectrum in these experiments are calculated. The obtained
experimental spectra demonstrate the amplification of 2H-NMR signals due to ODIP. Optimization of
the experimental conditions (concentration, temperature of the sample) for reproducible reception of
ODIP-type polarization was carried out. Despite the experimental difficulties, we obtained
amplifications of the NMR signals of the order of 40 during the experiment in a strong field. The
amplification of signals is obtained when creating a nonequilibrium spin polarization in a weak field.
Despite the difficulties in applying, ODIP method allows us to expand the range of
applications of spin hyperpolarization and work with deuterium nuclei.
Acknowledgements
This work has been supported by the Russian Science Foundation (Projects No. 15-13-20035) and
Russian Foundation for Basic Research (Projects No. 17-03-00932).
References 1. C.R. Bowers, D.P. Weitekamp // J. Am. Chem. Soc., (1987) 5541-5542
2. M.G. Pravica, D.P. Weitekamp // Chem. Phys. Lett., (1988) 255-258.
3. J. A. Aguilar, P. I. P. Elliott // Chem. Commun., 2007, p. 1183–1185
Poster 14
A solid state NMR & MD simulation study of water- octanol
mixtures confined in mesoporous silica
Bharti Kumari, [email protected]
a
Eduard-Zintl Institut für Anorganische und Physikalische Chemie, Technische
Universität Darmstadt, Alarich-Weiss-Str. 8, D-64287 Darmstadt, Germany
Prof. Dr. Gerd Buntkowsky
The investigation of water-alcohol interactions with surfaces at a molecular level is the basis to
understand the effect of confinement in porous material. This will be the basis to optimize separation
techniques such as lubrication, oil recovery and in enviornmental studies as elimination of
contamination and pollution control. In the present work, the behavior of water-octanol and its isomers
confined in the mesoporous silica SBA-15 is studied by a combination of solid-state NMR
spectroscopy and molecular dynamics simulations. Two dimensional 1H-
29Si FSLG-HETCOR NMR
spectra help to inspect the intermolecular interaction of these mixtures with the pore walls. This NMR
study reveals that the hydroxyl groups of octanol and water stay near the pore surface through
hydrogen bonds with silica sites, while the hydrocarbon chains are located in the range between
surface and center. These results are supported by MD simulation study as the Oxygen atom density is
high near the silica pore wall. The combination of NMR and MD simulations provides a clearer
picture on the structure of octanol/water mixtures in confined environment of mesoporous materials.
FIGURE 1. (a)Room temperature
1H-
29Si CP-MAS HETCOR experiment measured at 8 kHz
spinning of dried SBA-15 mixed with neat 1-octanol measured with a contact time of 9 ms. (b)
Number density profile of oxygens of water and 1-octanol molecules for 0, 10 and 30 mol% water
obtained at 425K.
Acknowledgements
The Forschergruppe FOR1583 and the iNAPO project financed by the Hessen State Ministry of
Higher Education have supported this work.
References [1] Bharti Kumari, Martin Brodrecht, Mayke Werner, Bob Grünberg, H.-H. Limbach, Sandra Forg, Elvira P. Sanjon, Barbara Drossel, Torsten Gutmann, Gerd Buntkowsky, 2018, submitted for publication
Poster 15
The Time-Resolved Electron Paramagnetic Resonance Study of
the Photoexcited Fullerenes Spin Polarization in Ionic Liquids
Ivan Kurganskii1,2
, [email protected] 1International Tomography Center SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Mikhail Yu. Ivanov, PhD student
Matvey V. Fedin, doctor of science, RAS professor
Ionic liquids (ILs) is a new class of solvent drawing significant interest because of their specific
physical and chemical properties. One of the properties is the ability of ILs for self-organization and
formation of heterogeneities on the nanometer scale that makes them useful for catalysis, drug
delivering etc. However, the mechanism of molecular-scale structuring of ionic liquids is still an
urgent problem of ionic liquids research. The EPR spectroscopy of spin probes is a good experimental
approach for this purpose because it provides the information about the structure of the solvent on the
molecular level as well as the information about the interaction of the probe with the environment. In
this work, we for the first time investigate capabilities of photoexcited triplet fullerenes to probe local
properties of ILs with Time-Resolved Electron Paramagnetic Resonance (TR EPR) as a detection tool.
The goal of the work is the study of spin polarization dynamics of fullerenes in various ILs. We
have selected C60 and its derivative phenyl-C61-butyric acid methyl ester (PCBM) as probes, toluene,
ortho-terphenyl and ILs [Bmim]BF4 and [C10mim]BF4 as solvents. The results of the work would be
beneficial for future use of the fullerenes as spin probes on ILs nanostructuring. The experiments were
performed on an X-band time-resolved EPR spectrometer.
The pseudorotations of Jahn-Teller axis influence the spin dynamics of C60 complicating the
interpretation of its spectra. Furthermore, C60 demonstrates the low solubility in the used ILs that
restricts the temperature range of the probe application. The
much less efficient relative to C60 pseudorotations of PCBM
as well as its high solubility in ILs make the use of the probe
more comfortable. The analysis of 2D TR EPR spectra of
PCBM shows that the spectral lineshape is sensitive to the
mobility of the probe in ILs providing the information about
their nanostructure. For example, the analysis proves the
simultaneous existence of slowly and fast relaxing fraction
of PCBM corresponding to the probes dissolved in molten
and frozen IL respectively (Fig. 1). The probe complements
other probes used earlier due to its larger size and capability
to high-sensitive TR EPR measurements up to room
temperature.
This work was supported by the Russian Science Foundation (No. 14-13-00826).
Fig. 1.Time evolution of PCBM
in IL [C10mim]BF4 at 200 K
Poster 16
Photo-CIDNP and Stability Studies on the
LOV Blue-Light Receptor Aureochrome
Patrick Kurle1, [email protected]
1Institute for Analytical Chemistry, Leipzig University, Leipzig, Germany
Prof. Dr. J. Matysik
Aureochromes is a blue-light sensing photoreceptors containing flavin mononucleotide (FMN) as
a chromophore in their LOV domains. In the naturally occurring proteins, light irradiation generates
the triplet state of the FMN cofactor (3FMN) which then rapidly reacts with a nearby conserved
cysteine to form a covalent adduct. [1] A cysteine-to-alanine mutant abolishes the adduct formation
and elongates the lifetime of 3FMN. This instead can induce a one electron transfer from a nearby
tryptophan residue (ca. 11Å edge-to-edge distance) and form a spin-correlated radical pair which can
be identified as photochemically induced dynamic nuclear polarization (photo-CIDNP) by solid and
liquid state NMR. [2,3]
In this thesis the generation of 13
C photo-CIDNP is explored in the LOV-C287S mutant of
Phaeodactylum tricornutum aureochrome with a uniformly 13
C-/15
N-labelled sidechain of tryptophan.
Signal enhancement is significant and selectively for the tryptophan side chain, i.e., the electron donor
of the radical pair. According to signal assignment and intensity comparison in the 13
C NMR
spectrum, we derived the electron spin density distribution at the indole ring could be determined.
Together with the solid-state photo-CIDNP effect, photo-degradation of FMN in the mutated
aureochrome and the LOV1-C57S mutant of Chlamydomonas reinhardtii phototropin was observed. It
was investigated whether additives could mitigate the photo-degradation and prolong the lifetime of
the protein. For this, small amounts of the biological reductant tris(2-carboxyethyl)phosphine (TCEP),
were added to the protein solutions and investigated under one hour continuous blue-light illumination
with UV/Vis spectroscopy and 31
P-NMR.
[1] C. W. M. Kay, E. Schleicher, A. Kuppig, H. Hofner, W. Rüdiger, M. Schleicher, M. Fischer, A. Bacher,
S. Weber, G. Richter, J. Biolog. Chem. 278, 13, 10973-10982 (2003).
[2] S. S. Thamarath, J. Heberle, P. J. Hore, T Kottke and J. Matysik, J. Am. Chem. Soc. 132, 15542-15543
(2010).
[3] G. Kothe, M. Lukaschek, G. Link, S. Kacprzak, B. Illarionov, M. Fischer, W. Eisenreich, A. Bacher, S.
Weber, J. Phys. Chem. B 118, 11622-11632 (2014).
Poster 17
EPR spectroscopy for gas sorption study in Metal-Organic
Frameworks
Diana Kuzmina1,2
1International Tomography Center SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Supervisor: PhD Alena Sheveleva
Metal organic frameworks (MOFs) are actively developed materials with enormous surface area
and modification potential. The synthesis of MOFs is less sophisticated compare to other porous
materials, therefore the variety of forms has been designed, and now physical properties of this
material have to be studied by modern methods. One of the promising applications for MOFs is gas
storage, especially dangerous ones and those from the atmosphere causing ecological and healthy
problems for millions of people. Adsorption of air pollutant gases at different MOFs is the topic of the
actual research.
Electron paramagnetic resonance (EPR) methods are already found their application for MOFs
research, despite the absence of EPR signal at variety of MOFs. There are two methods of EPR-silent
frameworks: doping paramagnetic metals into its structure and embodiment of small amount of
nitroxide radical spites post-synthetically (1 mol. per 1000 unit cells). The second certainly doesn‘t
influence the structure properties and this approach was chosen for actual research. TEMPO probe
molecules are used to scan the structure of the frame by a continuous wave (CW) and pulsed EPR
methods through molecular mobility inside the frame.
The first MOF for our research is ZIF (zeolitic imidazolate framework). It was chosen due to the
exceptional thermal (till 500 oC) and chemical stability. One of the most popular and chemically
studied ZIFs is ZIF-8. It has a cubic lattice structure and sodalite (SOD) topology with 11.6 Å and
3.4 Å diameter cavities. This structure is supposed to be applicable for gas separation and selective
adsorption, that is well suited for atmospheric problem tasks.
CW EPR technique was applied for TEMPO@ZIF-8 system filled with different gases
(CO2/O2/N2). Line shape analysis was made to demonstrate that the high quantity of adsorbed gas
inside the frame tends to increase the rotational correlation time of the system. Molecular dynamic
(MD) and TGA were made as supporting methods and have proved EPR results. [1]
Another system for observation is MFM-300(M2) with M = Al, Ga or In. This framework is
known for efficient CO2 and SO2 adsorption due to active μ2-OH groups inside the channel structure
and remarkable chemical stability to NOx adsorption, that can be the clue to serious ecological issues.
In-depth understanding of guest-host interaction is going to be obtained with CW EPR and pulse
techniques (ENDOR, HYSCORE). Systems TEMPO@MFM-300(M2) and dTEMPO@MFM-
300(M2), with deuterated spin probe, are now under our study.
By our research we have demonstrated the EPR is promising for characterization of novel MOF
materials.
Diana Kuzmina thanks RSF grant No 17-73-10320 and the Presidential Grant (No.
MK.3272.2017.3).
[1] A. M. Sheveleva, A. V. Anikeenko, A. S. Poryvaev, D. L. Kuzmina, I. K. Shundrina, D. I. Kolokolov,
A. G. Stepanov, M. V. Fedin, Probing Gas Adsorption in Metal-Organic Framework ZIF-8 by EPR of Embedded
Nitroxides, J. Phys. Chem. C2017, 121, 19880-19886
Poster 18
Calculation of the magnetic shielding tensor on 125
Te and 207
Pb nuclei inPbTe Irina Lushpinskaya
1Saint Petersburg State University, Department of Nuclear-Physics Research Methods
E-mail: [email protected]
Lead telluride is a semiconductor with a narrow slit long used for thermoelectric
applications [1]. Among the many ways to interrogate the state of semiconductors such as
PbTe, nuclear magnetic resonance (NMR) of both nuclei has been extremely valuable in
assessing the electronic state. For example, the Knight shift, which probes the interaction of
nuclear spins with conduction band carriers (electrons or holes), provided a direct measure of
carrier concentration. This readout can be performed even on samples that are not amenable to
transport studies. Such readouts could, in principle, aid in the development of novel materials
which cannot be produced as high quality thin films or single crystals. This potentially
important technological application is currently hampered, however, by inability to separate
Knight shift from chemical shift. From this perspective a correct calculation of chemical shift
is highly required.Here we report on the results of our calculations of chemical shift on 125
Te
and 207
Pb nuclei focusing on correct consideration of spin-orbital coupling (SOC), that could
be important for heavy nuclei.
The band structure and chemical shift calculations in PbTe were done using the full-
potential linearized augmented plane wave (FLAPW) method as implemented in WIEN2K
package. Calculations were carried out using the generalized gradient approximation (GGA)
with the exchange and correlation potential of Purdue-Berck-Ernzerhof (PBE), which is the
standard GGA potential for solids. A cutoff RMTKmax=7.0 for the plane-wave vector was used.
Here, Kmax is the plane-wave cutoff, and RMT is the muffin-tin radius, which is taken as 2.5
bohr for all atoms. SOC was treated as a second variational procedure with scalar relativistic
orbitals as a basis where states up to 8 Ry above the Fermi level were included in the basis
expansion. In all calculations, self-consistency was achieved with a tolerance in the total
energy of 0.1 mRy. For both ground state and NMR calculations a total number of 21×21×21
k-points was used.
PbTecrystallizes into a face centered cubic structure that with the space group Fm-3m
(# 225). Using the obtained lattice parameter value, the magnetic shielding tensor σ on both 125
Te and 207
Pb nuclei was calculated. In cubic crystal σxx = σyy= σzz = σiso. Further, for 125
Te
the calculated absolute chemical shift was compared with experiment. It should be noted that
in experiment one determines not the absolute but the relative chemical shift:
For 125
Te NMR frequency is normallycalibratedusingtheunifiedscale Ξ
relativetoadimethyl telluride solution TeMe2. The absolute value for TeMe2is equal to
3388 ppm as determined in Ref. [3]. The relative chemical shift for 125
Te can be used for
correct separation chemical and Knight shift in experiment [4].
Acknowledgements
All calculations were carried out at the Computing Center of the Research Park of Saint
Petersburg State University.
References
[1] LaLonde, A. D.; Pei, Y.; Wang, H.; Snyder, G. J. Mater. Today 14 (2011) 526.
[2] R. Dalven, Infrared Phys. 9 (1949) 141.
[3] Y. Ruiz-Morales, G. Schreckenbach, T. Ziegler. J. Phys. Chem. A101 (1997) 4121. [4] R.E. Taylor, F.Alkan, D.Koumoulis, M.P. Lake, D. King, C.Dybowski,L.S. Bouchard. J.
Phys. Chem. A, 117 (2013) 8959.
Poster 19
Cofactor binding to methyltransferase WBSCR27
Sofia Mariasina, [email protected]
M.V.Lomonosov Moscow State University, Moscow, Russia
Dr Vladimir I. Polshakov
WBSCR27 (27 kDa, 240 a.a.) protein is a product of one of the genes associated with the
Williams-Beuren Syndrome – rare genetic disorder characterized by mental and physiological
problems including severe cardiovascular abnormalities.
Bioinformatics predict that WBSCR27 is S-adenosyl-L-methionine (SAM) dependent
methyltransferase. SAM contains very reactive trivalent sulfur atom bound to CH3 group, and it
participates as a methyl donor in variety of methylation reactions. Upon the methyl transfer, SAM
converts to S-adenosyl-L-homocysteine (SAH) with divalent sulfur atom.
We found that after expression in E.coli cells and subsequent isolation and purification,
WBSCR27 samples contain tightly bound SAM, which cannot be removed even after 3 days of
dialysis. However, WBSCR27 catalyzes decomposition of cofactor with elimination of adenine
moiety. This process allows us to obtain WBSCR27 protein in apo-form.
NMR spectra of apo-form of WBSCR27 and its complex with SAM show numerous differences.
Analysis of the set of 3D heteronuclear NMR spectra allowed us to obtain 1H,
15N, and
13C chemical
shift assignments and to determine protein secondary structure and backbone mobility in both
WBSCR27 forms. Chemical shifts of the complex were deposited to the BioMagResBank under the
accession number BMRB-27417. If was found that SAM binding is accompanied by the formation of
fourα-helices at the N-terminal protein region. WBSCR27 residues involved in SAM-binding have
been determined using several complementary NMR techniques. 3D structure determination of
WBSCR27 protein in both binary complex with SAM and in apo-form is currently in progress.
Acknowledgements: studies were supported by the Russian Foundation for Basic Research (grant
17-04-00852).
Poster 20
Magnetic Field Effect of xanthone and DABCO in a micelle
Taisuke Matsuo1, [email protected]
1Graduate School of Science and Engineering, Saitama University, Saitama, Japan
Prof. Kiminori Maeda1
After the radical pair mechanism was proposed as the mechanism of the magneto reception for the
animal navigations, magnetic field effect in low field region has been studied extensively for seeking
the condition in which the system could sense the field as weak as the earth‘s magnetic field.
However, so far a few examples of the magneto reception of very small field has been reported.[1]
We still don‘t know what is the most crucial factor for the sensitivities to low magnetic field.
In the present poster, we report low magnetic field effect in the photochemical reaction of xanthone
and DABCO in micellar solution. Goez et al. previously reported that this system shows large
magnetic field effect in high magnetic field.[2] However, any
study focusing on the low field effect (LFE) has not been
reported. However, the following characteristics of the system
motivate us to try the precise analysis of the LFE.
1). Unbalance of the size of the hyperfine coupling constants
between xanthone anion radical and DABCO cation radical.
2). The polar molecule would diffuse on the surface of the
micelle and would not have large interference by the
fluctuating electron spin interactions.[2]
3). Many identical protons (12H) on DABCO cation radical
provides high degeneracy of the nuclear spin states.
Time-Resolved ESR spectrum observed in the present system
is shown in Fig. 1(a). The totally emissive polarization due to
triplet mechanism indicates the triplet born radical pair
formation. Recently we have built a new transient absorption
set-up by diode laser and balanced photodetector.[3] Thanks
to the stability of the pump and probe lasers, we could obtain
very good S/N on the MARY spectrum of a few percent in 10-3
order of the transient absorption. Fig.
1-(b) shows MARY spectrum. We could observe negative magnetic field effect i.e. LFE. Now we can
analyze the shape of the MARY spectra in various conditions comparing with theoretical calculations. References
[1] K. Maeda, K. Henbest et al. Nature, 453, 387-390 (2008).
[2] M. Goez, Kevin B. Henbest, et al., Chem. Eur. J., 15, 6058-6064(2009).
[3] K. Arakawa, K. Maeda, Spin Chemistry Meeting 2017
Poster 21
Development of the Fourier Transform Infrared
Spectroscopy in High Magnetic Fields
Jana Midlíková1, 2
1CEITEC, Brno, Czech Republic
2BUT, Brno, Czech Republic
Ing. Petr Neugebauer, PhD.
Infrared spectroscopy is certainly one of the most important analytical technique available to
scientists nowadays. It is a technique based on the vibrations of the atoms of a molecule [1]. From a
scientific point of view, far-infrared (FIR) energy region in high magnetic fields is of particular
importance, since it covers the magnetic resonances such as spin resonance, cyclotron resonance and
other important effects [2]. Therefore, the combination of the Fourier Transform Infrared spectroscopy
in FIR region and high magnetic field allows to study magnetic resonance phenomena such as
Electron Paramagnetic Resonance (EPR), which is an important method for investigation of Single-
Molecule Magnets (SMMs). The main goal of this project is development of Fourier Transform
Infrared Spectroscopy in High Magnetic Fields, because this instrumentation will allow to study
EPR through the use of FIR region, lying adjacent to the microwave region, and thus broaden typical
microwave range for investigation of SMMs, especially single lanthanide ions, because their
anisotropy barriers lie in the range of a few hundred wavenumbers [3].
[1]STUART, Barbara. Infrared Spectroscopy: Fundamentals and Applications. John Wiley, 2004
[2]High Magnetic Field Science and Its Application in the United States: Current Status and Future
Directions. National Academies Press, 2013.
[3]HAAS, Sabrina. Far-infrared spectroscopy of lanthanide-based molecular magnetic materials. 2015.
Poster 22
Hydrogen-bonded self-associates of phosphoric and phosphinic
acids studied by 31
P and 1H NMR in aprotic solution
V. V. Mulloyarova1, I. S. Giba
1Institute of Chemistry, Saint Petersburg State University, Saint Petersburg, Russia
2Department of Physics, Saint Petersburg State University, Saint Petersburg, Russia
P. M. Tolstoy, PhD, associate professor
Phosphorus-containing acids can form different cyclic self-associates or infinity chains. In gas
phase the cyclic self-associates are formed predominantly, while the chains are often formed in solid
state. Much less is known about the self-association of phosphinic and phosphoric acids in aprotic
solution. We studied the self-assembly of diphenylphosphoric and dimethylphosphinic acids in
solution in CDF3/CDClF2 by low-temperature (down to 100 K) 31
P and 1H NMR. At the low
temperature the molecular and proton exchange is slowed down and it becomes possible to resolve the
NMR signals of associates with different stoichiometry. Partial H/D replacement in mobile proton
sites was used to determine the types of self-associates. As a result of H/D replacement in one of the
hydrogen bonds its length changes and due to the coupling between neighboring bonds, the length of
neighboring hydrogen bonds changes as well. This replacement leads to H/D isotope effects on 1H
NMR chemical shifts in various isotopologs and the number of signals in 1H NMR spectra increases
(Fig., right spectra of (PhO)2POOH). Thus, it was established that dimethylphosphinic and
diphenylphosphoric acids form cyclic dimers and cyclic trimers (Fig., right) at low temperature in
aprotic solution. The integral intensities of 1H (Fig., left) and
31P NMR signals indicate that the
equilibrium is shifted towards the formation of trimers (ratios are ca. 7:1 for dimethylphosphinic and
3:2 for diphenylphosphoric acids). Besides, from the values of 1H NMR chemical shifts is could be
concluded that hydrogen bonds in cyclic trimers are stronger (shorter). In cyclic trimer there is
reversible degenerate triple proton (deuteron) transfer, which is fast in the NMR time scale.
Acknowledgements
This work has received financial support from the RFBR Grant 17-03-00590.
[1] V.V. Mulloyarova, I.S. Giba, M.A. Kostin, G.S. Denisov, I.G. Shenderovich, P.M. Tolstoy. Phys. Chem.
Chem. Phys., 2018, 20, 4901-4910.
[2] J.S. Siegel, F.A.I. Anet,. J. Org. Chem. , 1988, 53, 2629–2630.
ppm13.213.413.613.814.014.214.414.614.815.0
43% D
0% D
dimertrimer
HH HD
HHD
HHH
HDD
T=100 K
CDF3/CDF2Cl
Poster 23
EPR study of powders of the doped tricalcium phosphate and
hydroxyapatite
Fadis Murzakhanov1, [email protected]
1Kazan Federal University, 18 Kremlevskaya Str., Kazan, Russia
Ass. Prof., Dr. Marat Gafurov
A field of my interest at present is an investigation of powders and nanosized powders of synthetic
hydroxyapatite (HA, Са10(PO4)6(ОН)2) and tricalcium phosphate (TCP, Ca3(PO4)2) doped with various
ions in different concentrations using X-band EPR. HA and TCP are the most important biomaterials
widely used in dentistry and orthopedics, to restore bone defects and as materials for coating metal
implants [1]. HA and TCP are non-toxic, have high biocompatibility, osteoconductivity, good
mechanical properties, etc. [2]. These properties could be tuned by doping the species by metal cations
The goal of the modern material (medical) science – to create multifunctional, personalized materials
by using HA, TCP and their mixture as matrices.
We have investigated Mn2+
doped HA and TCP powders with the manganese concentration in the
range 0-5 mol %. The main parameters of the spin Hamiltonian Ĥ = gβH0Ŝ + D*(S2
z –S*(S+1)/3) +
E*(S2x+S
2y) + AÎŜ [3] were determined (g-factor, zero-field parameters D and E of the axial crystal
field, the value of the isotropic hyperfine interaction Aiso). Exchange narrowing with concentration
was revealed. The corresponding coefficients of the exchange interaction were calculated. EPR
lineshapes were approximated. Intensive signals with the resolved hyperfine structure at g ≈ 4.8 and
g ≈ 10 are observed which may be due to the presence of different, structurally nonequivalent
positions for Mn2+
ions for Ca2+
substitution in HA and TCP structures [3]. Additional experimental
studies are needed to describe the powder spectra and structures at g ≈ 4.8 and g ≈ 10.
[1] Mayer, I. Cristal structure and EPR study of Mn-doped β–tricalcium phosphate / I.Mayer, S.Cohen,
S.Gdalya et al. // Material Research Bulletin. – 2008. – V. 43. – P.447-452.
[2] Bose, S. Understanding of dopant–induced osteogenesis and angiogenesis in calcium phosphate ceramics /
S.Bose, G.Fielding, S.Tarafder, A.Bandyopadhyay // Trends Biotechnol. – 2013. – V. 31, № 10. – P.594-605.
[3] Klyava, Ya.G. EPR spectroscopy of disordered solids / Ya. G. Klyava. – Riga: Zinatne, 1988. - 320 p.
Poster 24
Theoretical treatment of pulsed Overhauser DNP: off-resonance
excitation and pulse shape effects
Egor A. Nasibulov1,2
, Alexey S. Kiryutin1,2
, Alexandra V. Yurkovskaya1,2
,
Hans-Martin Vieth1,3
, and Konstantin L. Ivanov1,2
1International Tomography Center, Siberian Branch of the Russian Academy of Science,
Institutskaya 3A, Novosibirsk, 630090, Russia
2Novosibirsk State University, Pirogova str. 2, Novosibirsk, 630090, Russia
3Freie Universität Berlin, Arnimallee 14, Berlin, 14195, Germany
E-mail:[email protected]
DNP is a powerful method to create non-thermal polarization of nuclear spins, thereby
enhancing their NMR signals. The DNP effect is due to transfer of the electron spin polarization to
nuclear spins in the presence of MW-pumping; the NMR enhancement is proportional to the ratio of
the magnetogyric ratios of electron e and nucleus n. In the case of Overhauser-type DNP (DNP in
liquids) the NMR signal enhancement is =1+fse/n with , f and s being the coupling factor,
leakage factor and saturation factor, respectively. It is well-known that MW-pumping, required for
reaching maximal values, can cause substantial heating of the sample. For this reason, using pulsed
techniques of pumping instead of cw-pumping is of great interest [1].
Here Overhauser-type DNP formed by a periodic sequence of EPR-pulses is discussed. Earlier
[2] the case of a single ideal pulse per period was discussed and an elegant general expression for the
NMR enhancement has been obtained. The expression for the enhancement was shown to be similar to
that known for cw-pumping with the saturation factor re-defined as the deviation of the electron spin
magnetization from its equilibrium value averaged over the cycle of the pulse sequence. In this work a general theoretical approach to pulsed Overhauser-type DNP is presented. The
theory can treat pulsed irradiation of EPR transitions for an arbitrary periodic pulse sequence. The
NMR enhancement is analyzed in detail as a function of the EPR-pulse length for ideal pulses and
pulses with a finite rise-time. It is shown that one can achieve the maximal theoretically allowed NMR
enhancement for pulsed pumping even when the duty cycle of pumping is low. Characteristic
oscillations of the DNP enhancement are found when the pulse length is stepwise increased,
originating from the coherent motion of the electron spins driven by the pulses. The dependence of the
DNP effect on the duty cycle, pulse length and electron spin relaxation times has been studied in
detail. Once the lines in the EPR spectrum are inhomogeneously broadened, higher DNP effects are
expected in the pulsed pumping mode than in the cw-mode for the same total power of microwave
irradiation.
In multicomponent EPR spectra pulsed pumping allows one exciting even spectral
components, which are far from resonance with offsets exceeding B1; thus the enhancement is higher
than for cw-pumping with same B1. The contribution from off-resonant components and its
dependence on the pulse sequence parameters were analyzed. Heisenberg exchange can increase the
contribution from off-resonant components thus increasing the total NMR enhancement. Experimental
low-field DNP data are in good agreement with this theoretical approach.
[1] M. Alecci, D.J. Lurie, J. Magn. Reson. 1999, 138, 313-319.
[2] E.A. Nasibulov, K.L. Ivanov, A.V. Yurkovskaya and H.-M. Vieth, Phys. Chem. Chem. Phys.,
2012, 14, 6459-6468.
This work has been supported by the Russian Foundation for Basic Research (projects No. 18-33-
00251).
Poster 25
Simulation of pulse RF sequences for MRI using contrast
agents based on iron oxide nanoparticles
A.V. Nikitina, [email protected]
Department of Physics, St.-Petersburg State Electrotechnical University, St.-Petersburg,
197376, Russia
Yu.V. Bogachev, PhD
This research was carried out on NMR relaxation of protons of biological liquids models in the
presence of magnetic nanoparticles (MNPs) based on iron oxide of different composition and with
different shells. Based on the obtained relaxation characteristics [1], a simulation program was
developed to optimize the parameters of pulse RF sequences for MRI studies both in the absence of
MNPs and in the presence of MNPs.
This program implements three sequences: «spin echo», «inversion-recovery», and «gradient
sequence». The program provides an opportunity to study graphs of the dependence of the intensity of
the MR signal on the parameters of the sequence for white, gray matter and cerebrospinal fluid.
When using magnetic nanoparticles, a graph of the dependence of the MR signal intensity on the
sequence parameter for five MNPs concentrations is also displayed. Also in the program window are
simulated images showing the intensity of the signal on a scale of gray.
Using this program, the user can evaluate the impact of pulse sequence parameters on the contrast of
MR images, choose the optimal sequence parameters and determine the necessary concentration of
MNPs to improve the contrast of MR images.
The developed program of control of parameters of pulse RF sequences can be used for training of
students and medical personnel too.
The obtained results can be used for medical diagnostics with the use of new contrast agents based on
magnetic nanoparticles in vivo and in vitro, and in the development of new methods for magnetic
resonance theranostics.
Acknowledgements. This work was supported by the Ministry of education and science of the Russian
Federation (project 3.6522.2017).
[1] Bogachev Yu.V., Nikitina A.V., et al.: Appl. Magn. Resonance, 48, I.7, 715-722 (2017).
Poster 26
Studying intrinsically disordered protein lactaptin by PRE
S. S. Ovcherenko 1, 2
1 N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry of Siberian Branch of
Russian Academy of Sciences
2 Novosibirsk State University
A. V. Shernyukov 1, 2
, Dr.
Lactaptin is a recombinant analogue of the proteolytic fragment of the human milk protein κ-
casein, which has apoptotic activity to tumor cells and is also a membrane-active peptide capable of
direct penetration into eukaryotic cells [1].
Paramagnetic relaxation enhancement (PRE) is a common NMR application for protein structure
determination, including the analysis of intrinsically disordered proteins‘ (IDPs‘) tertiary structures in
solution. General idea of this method for nonmetal binding proteins is the introduction of an extrinsic
paramagnetic center to a specific site of protein. The presence of the paramagnetic spin label leads to
an enhancement in the transverse relaxation rates R2 depending on the inverse sixth power of the
distance (1/r6) between the unpaired electron and the observed nucleus presence. The distance
information between the spin label and NMR active nuclei can be determined by the measuring of
increased R2 relaxation rates. In the case of random coil state the expected profile calculated using the
mean field approximation to an unperturbed chain, predicts that the PRE should extend to ~15 residues
from the site of a nitroxide spin label [2]. On the other hand the presence of impact PRE on residues
located far from the site suggests the existence of a collapsed state of protein with no coherent three-
dimensional structure.
Recently, it was demonstrated that lactaptin belongs to IDP and also the most ordered site in the
peptide with the propensity to alpha helical structure by SSP method was found. The protein has a
single cysteine residue located near the site. In this work we investigated lactaptin, modified at
cysteine with MTSL, by PRE. The results of this work will be presented in a poster.
This work is supported by the Ministry of Education and Science of Russian Federation (state
contract no 2017-220-06-7355)
[1] Semenov D. V., Fomin A. S., Kuligina E. V., Koval O. A., Matveeva V. A., Babkina I. N., Tikunova N.
V., Richter V. A. Recombinant analogs of a novel milk pro-apoptotic peptide, lactaptin, and their effect on
cultured human cells The protein journal. – 2010. – V. 29. – No. 3. – P. 174–180.
[2] Felitsky D. J., Lietzow M. A., Dyson H. J., Wright P. E. Modeling transient collapsed states of an
unfolded protein to provide insights into early folding events. Proc. Natl. Acad. Sci. U.S.A. – 2008, –V. 105. – P.
6278-6283.
Poster 27
Glycyrrhizin induced phase transitions in
1,2dipalmitoylphosphatidylcholine lipid bilayer studied by 1H
NMR and MD simulation
E. D. Paramonova1,2
, L. A. Kichigina1,2
, E. A. Shelepova1, 2
, A. V. Kim1,2
,
S.S. Khalikov3, O. Yu. Selyutina
1, N. E. Polyakov
1
e-mail: [email protected]
1Institute of Chemical Kinetics and Combustion, Institutskaya St., 3, 630090,
Novosibirsk, Russia
2Novosibirsk State University, Pirogova St., 2, 630090, Novosibirsk, Russia
3Nesmeyanov Institute of Organoelement Compounds of Russian Academy of
Sciences, Vavilova St., 28, 119334, Moscow, Russia
Scientific advisor: Nikolay Polyakov, PhD
Phase transitions in lipid bilayer play an important role in the cell life and in transmembrane transport of ions and drug molecules. It is considered that the local changes of lipid composition and the presence of phase borders could influence on the cell membrane permeability. In the present study we have tried to understand the mechanism of action of glycyrrhizin on drugs bioavailability by studying the mechanism of its influence on the phase transitions of lipid membrane. We have studied the effect of GA on phase transition temperature (Tm) by
1H-NMR spectroscopy and the aggregation of
GA in dipalmitoylphosphatidylcholine (DPPC) membrane by MD simulation.
1H-NMR experiments were done for GA concentrations 0.25, 0.5 and 0.75 mM in D2O at
pH=5.3. We observed the increase of Tm under the GA concentration 0.25 mM, but the decrease under the higher concentrations.The width of temperature range also changed with the concentration. It decreases at the concentration 0.5 mM and increases at the concentration 0.75 mM. This could be caused by the fact that GA concentration comes close to critical concentration of micelle formation (~1 mM) [1].Also the experiments were performed in buffer solution at with pH=7.0 with GA concentration 0 and 0.5 mM, and the results are in agreement with experiments in distilled water. Effect of cholesterol was also studied.
The MD simulation indicated the formation of long-lived GA associates consisting of 3 or 4 GA molecules. This associates enhance lipid order of the DPPC bilayer. Such enhancement also was observed for DPPC bilayer with 4 not associated GA molecules. Moreover, MD modeling predicts local thinning of DPPC bilayer near the location of GA associates.
Thus, in the present study the effect of lipid ordering in DPPC membrane in the presence of glycyrrhizin was shown by MD simulation and
1H-NMR spectroscopy techniques. We observed the
increase of phase transition temperature in the presence of GA.These results shed light on the mechanism of drugs bioavailability enhancement in the presence of glycyrrhizin.
The reported research was funded by Russian Foundation for Basic Research, grants №15-29-05792, 18-03-00045
[1] Petrova, S. S. Self-Association of Glycyrrhizic Acid. NMR Study. / S. S. Petrova, A. A. Schlotgauer, A.
I. Kruppa, T. V. Leshina // ZeitschriftfürPhysikalischeChemie - 2016 - Vol. 231 - P. 1-17.
Poster 28
Ionic motions in [(C4H9)4N]BF4, [(C4H9)4N]I and composite
solid electrolytes [(C4H9)4N]BF4 – A (A – Al2O3, SiO2)
Polyantsev M.M.1, [email protected]
1Institute of Chemistry, FEB RAS, 159, Pr. 100-letiya Vladivostoka,
Vladivostok, 690022, Russia
Supervisor: Dr. Slobodyuk A.B.
Orientationally-disordered phases
receive considerable scientific interest due to
their unusual physical and chemical properties
[1]. In particular, the reorientational disorder
can facilitate the ionic diffusion through the
―paddle wheel mechanism‖. The diffusion can
be further enhanced by mixing the source
compound with the micro- or nanosized oxide
which leads to formation of the extrinsic
defects on the interphase boundary.
Bu4NBF4 (Bu=C4H9)is an example
of the orientationally-disordered compounds.
All atoms in Bu4NBF4 have naturally
occurring isotopes with magnetic moments. It
was established by means of 1H,
19F NMR that
Bu4NBF4 is characterized by several forms and stages of ionic motions (Fig. 1), including
reorientations of atomic groups and diffusion of the BF4- ion. The phase transition into the ion-
conducting modification is accompanied with dramatic changes both in 19
F and 1H second moments.
The 19
F NMR spectra of the Bu4NBF4 – Al2O3 and Bu4NBF4 – SiO2 composites contain one
or two components. One of the components can be attributed to the inner (unmodified) volume of the
salt. Other component probably corresponds to the interphase Bu4NBF4 layer. Chemical shifts of the
components are -152 and -193 ppm, respectively. The temperature dependence of the components
second moments differs considerably from that of the Bu4NBF4 indicating that a number of atomic
environments exists in the composites.
The changes of 1H NMR spectra of Bu4NI with temperature below the phase transition
temperature (118 o
C) are insignificant. The Lorentzian shape of the spectra emerging above this point
may indicate that the translational motions of the complex cations are taking place. The symmetry of
the local environment of iodine is low and the second-order spectra are registered for both
modifications of the compound. The width of the central transition (½↔-½) component constitutes
~1.6 MHz at 300 K varying with the change of temperature. Large width of the spectrum required
sweeping of the central frequency through the whole spectrum band with 100 kHz steps to record the
spectrum. The quadrupole coupling constant (CQ) varies from 33 to 29 MHz between 250 and 350 K
while asymmetry parameter ηQ remains equal to 2.34.
[1] Parsonage N.G., Staveley L.A.K. Disorder in Crystals. Clarendon, Oxford, 1978. 298 P.
150 200 250 300 350 400
0
10
20
30
40
50
60
M2(
19
F), kHz2
T, K
0
500
1000
1500 M
2(
1
H), kHz2
Fig. 1. Temperature dependencies of the 1H,
19F NMR
spectra second moment of the Bu4NBF4.
Poster 29
NMR Studies on Blue Light Receptor Proteins and Model
Systems
Nils Pompe1, [email protected]
1Albert-Ludwigs University, Institute of Physical Chemistry, Freiburg i. Br., Germany
Prof. Dr. Stefan Weber
The blue light response of many organisms, including plants and animals, is mediated by blue
light receptor proteins, such as LOV or BLUF domains. They all share a flavin cofactor as common
feature, acting as a chromophore, which exhibits a strong absorption maximum in the blue light
region. Most of the light-induced protein reactions depend on the formation of a transient radical pair,
comprising the isoalloxazine moiety of the flavin and aromatic amino acids in close proximity to the
cofactor [1].
Photo-CIDNP spectroscopy is an excellent way to probe these radical pair reactions by NMR [2].
Although the lifetime of the radical pairs can be on the timescale of a few ns, the CIDNP effect,
originating from hyperfine couplings of nearby nuclei to the unpaired electrons of the radical pair, can
be observed in NMR spectra in the form of anomalous signal intensities and/or sign changes. Further,
standard protein experiments can be used to investigate light-induced structural changes in the proteins
on the NMR timescale.
My research project focusses on the light-dependent NMR investigation of blue light receptor
proteins and model systems. To extend the possible range of experiments to larger proteins and lower
temperatures, a CIDNP setup under MAS conditions is currently under development. Further,
time-resolved CIDNP experiments are performed to determine the electronic structure of the
components forming the radical pair, either bound to the protein or free in isotropic solution [3].
[1] Nohr, D., Rodriguez, R., Weber, S. and Schleicher E., Front. Mol. Biosci.2, 49 (2015).
[2] Kothe, G., Lukaschek M., Link, G., Kacprzak S., Illarionov, B., Fischer, M., Eisenreich, W., Bacher, A.,
Weber, S., J. Phys. Chem. B
[3] Kiryutin, A. S., Morozova, O. B., Kuhn, L. T., Yurkovskaya, A. V. and Hore, P. J., J. Phys. Chem. B111,
11221–11227 (2007).
Poster 30
Out-of-phase ELDOR study of charge separation in organic
photovoltaic composites
Alexander A. Popov1,2
1Institute of Chemical Kinetics and Combustion of SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Dr. Leonid V. Kulik
Organic photovoltaic (OPV) cells have become perspective and active developing field of the
solar energy technology. The cells based on a composites of conducting polymers – electron donors,
and fullerene derivatives as acceptor reveal power conversion efficiency up to 10%. However, the
detailed mechanism providing such a high efficiency remains unclear what makes it difficult to
intentionally design a cell with desired properties.
The aim of this work is to develop a technique allowing to observe photoinduced charge transfer
state (CTS), a weakly coupled electron-hole pair preceding to completely separated charges, in OPV
composites so as to measure distance distribution of charges and how it evolutes in time. Obtaining
such an information for different composites is highly important for developing a general theory of
charge separation.
Out-of-phase Electron Double Resonance (OOP ELDOR) is a reasonable choice to reach the goal.
Interpreting ELDOR data one can estimate spin-to-spin interactions between hole and electron
radicals, both dipole and exchange, and therefore find out the structure of CTS. Also performing the
experiment with different delays after photoexcitation gives an opportunity to observe CTS at different
stages of charge separation and, thus, study kinetics of charge dissociation and recombination.
In this work the method of OOP ELDOR has been applied to OPV composites for the first time.
The data have been measured for a set of polymers, inlcluding benchmark polymer P3HT and high-
performance PCDTBT polymer, in conjuction with the PCBM acceptor. The data were processed
using Tikhonov regularization approach and corresponding electron-hole distance distributions have
been obtained.
Poster 31
Using optimal control methods with constraints to generate
singlet states in NMR
Bogdan A. Rodin1,2
1Novosibirsk State University, Novosibirsk, Russia
2International Tomography Center SB RAS, Novosibirsk, Russia
Konstantin L. Ivanov, Dr. Sci., Professor
Singlet state NMR is receiving increasing attention because of the attractive
possibility to generate long-lived spin order. Such a spin order can be used for investigating
slow dynamics, diffusion and transport in NMR and MRI. One of the problems associated
with LLSs is to develop a general and efficient method for generating and observing such
states. Specifically, for running experiments with singlet LLSs a technique is needed, which
can perform the magnetization-to-singlet (M2S) conversion and the reverse S2M conversion.
Here we propose a method for optimizing the performance of the APSOC
(Adiabatic-Passage Spin Order Conversion) technique, which can be exploited in NMR
experiments with singlet spin states. In this technique magnetization-to-singlet conversion
(and singlet-to-magnetization conversion) is performed by using adiabatically ramped RF-
fields. Optimization utilizes the GRAPE (Gradient Ascent Pulse Engineering) approach, in
which for a fixed search area we assume monotonicity to the envelope of the RF-field. Such
an approach allows one to achieve much better performance for APSOC; consequently, the
efficiency of magnetization-to-singlet conversion is greatly improved as compared to simple
model RF-ramps, e.g., linear ramps. We also demonstrate that the optimization method is
reasonably robust to possible inaccuracies in determining NMR parameters of the spin system
under study and also in setting the RF-field parameters. The present approach can be
exploited in other NMR and EPR applications using adiabatic switching of spin Hamiltonians.
This work has been supported by the Russian Science foundation (grant No. 14-13-
01053).
Poster 32
A highly versatile automized gas injection setup
for in-situ NMR - applicatons to PHIP and SABRE
Grit Sauera, Alexey S. Kiryutin
b and Gerd Buntkowsky
a.
aTechnical University Darmstadt, Eduard-Zintl Institute for Inorganic and Physical
Chemistry, Alarich-Weiss Straße 8, D-64287 Darmstadt, Germany bInternational Tomography Center, Institutskaya 3A, 630090 Novosibirsk, Russia
Para-Hydrogen Induced Polarization (PHIP) and Singnal Amplification By Revercible
Exchange (SABRE) are established hyperpolarization methods for signal amplification in
NMR and MRI. The signal amplification of both methods is based on spin polarization
transfer from a para-H2 molecule to a target molecule. This requires a catalytic reaction with
the parahydrogen, which typically occurs at a transition metal catalyst. Several factors are
involved in the efficient transfer of spin polarization in solution, such as a suitable substrate
and a corresponding catalyst, but also the amount of dissolved para-H2 in a given time is a
crucial factor. The kinetics of the catalytic reaction determine the efficiency of signal
amplification. For a detailed investigation of this fast reaction kinetics a setup (Figure 1) was
developed, which can inject gases such as para-H2, in a fast, precisely and computer-
controlled manner, into the sample tube placed in the NMR probe.[1]
In addition, an inert gas
such as He or N2 can be applied to degas the sample solution or to stop the reaction. The gases
are controlled by magnetic solenoid valves, which are synchronized with fast electric TTL
(Transistor-Transistor Logic) pulses and thus can be integrated into the NMR pulse program.
With this device, it is possible to achieve hydrogen saturation at pressures of 0-8bar in the
solution within less than 10s. NMR spectra can be taken immediately after hydrogen injection
with a delay of less than 1s. Due to the computer-controlled gas injection, well reproducible
polarized spectra (relative error of ± 3%) with a high spectral resolution can be achieved,
which allows quantitative NMR measurements. Three applications of this setup are shown,
namely the PHIP kinetics, a SABRE and a PANEL (PArtially Negative Line) experiment.[2]
A
B
FIGURE 1.Scheme of the Gas Injection Setup and pictures of the Switching part (A) and the Operation part (B)
Acknowledgements
This work has been supported the German Research Foundation under contract BU 911-
22-1 and by the Russian Science Foundation (grant No. 15-13-20035)
References
[1] Kiryutin, A. S.; Sauer, G.; Hadjiali, S.; Yurkovskaya, A. V.; Breitzke, H.; Buntkowsky,
G., J. Magn. Reson. 2017,285, 26-36.
[2]Kiryutin, A. S.; Sauer, G.; Yurkovskaya, A. V.; Limbach, H.-H.; Ivanov, K. L.;
Buntkowsky, G., J. Phys. Chem. C 2017,121 (18), 9879-9888
Poster 33
NMR-relaxation study of glycyrrhizin-flavonoids interaction
A. A. Schlotgauer, N. E. Polyakov1,
Russia, Novosibirsk, Voevodsky Institute of Chemical Kinetics and Combustion of SB RAS
Scientific supervisor: Prof. N. E. Polyakov
It is known that the spin-lattice T1 and spin-spin T2 relaxation times are very sensitive to the
intermolecular interaction and the diffusion mobility of molecules. This is why NMR-relaxation
technique became a powerful instrument to study non-covalent inclusion complexes of drug molecules
with various drug delivery systems (DDS). This is due to the change of the rotational correlation time
τc in the complex, which is estimated by the Stokes-Einstein-Debye τc = 4πa3η/3kT. After moving the
―guest‖ molecule inside the complex, the relaxation times of its protons significantly reduced by
slowing the diffusion and rotational mobility. DDS are widely used in pharmacology to improve the
solubility, stability and bioavailability of low soluble drugs. In the present study we used this approach
to study non-covalent interaction of glycyrrhizin as novel DDS with two low soluble flavonoids,
dihydroquercetin and puerarin. Glycyrrhizin or glycyrrhizic acid (GA) is a triterpene saponin extracted
from the licorice root. Glycyrrhizin has a number of properties that make it an attractive delivery
system. The key feature is the amphiphilicity of glycyrrhizin molecule: the hydrophilic part consists of
glucose rings, hydrophobic one is a glycyrrhetic acid residue. Owing to this, glycyrrhizic acid is
capable to form micelles in water solution and "host-guest" complexes with various hydrophobic
molecules.
Using NMR relaxation method we have shown the formation of inclusion complexes of
dihydroquercetin and puerarin with the disodium salt of GA in water solution. From the concentration
dependence of the relaxation time at various temperatures, the stability constants and thermodynamic
parameters of the inclusion complexes were estimated. К(dihydroquercetin) = 125±20 М-1
and
К(puerarin) = 480±50 М-1
at T = 30 C. Both dihydroquercetin and puerarin complexes with disodium
salt of GA demonstrate an increase in the stability constant with increasing temperature, which
indicates the predominant contribution of the entropy factor to the change in free energy during
complexation.
Poster 34
Data Processing in a Terahertz Magnetic Resonance
Spectrometer
Matúš Šedivý1, [email protected]
1Central European Institute of Technology, Brno, Czech Republic
Ing. Petr Neugebauer, Ph.D.
Magnetic resonance (MR) is a well-known phenomenon since thefirst half of the last century. The
most common kinds of MR are a nuclear magnetic resonance (NMR) and an electron spin resonance
(ESR). In both cases, similar principles apply. Due to the stricter technological requirements of
microwave instruments for the ESR, NMR techniques such as Magnetic Resonance Imaging (MRI)
have expanded more among research society [1]. As the result of advances in microwave technology,
a method called High Frequency Electron Spin Resonance (HFESR) spectroscopy become widely
accessible in recent years [2].
Our aim is to build a multifunctional broadband ESR spectrometer, which along with common
methods will allow us to utilize THz rapid frequency scan method (European Research Council
Starting Grant THz-FRaScan-ESR). This new method enhances the relation between signal-to-noise
ratio (SNR) and acquisition time, which leads to clearer results and faster measurements. However,
more demanding post-processing is needed due to distortion of the detected signal in form of
oscillations called ―wiggles‖. This can be handled by deconvolution of the signal into reconstructed
ESR spectrum [3]. Processing of a large amount of data in a short time is one of many challenges
towards a fully functional spectrometer. The spectrometer will be capable of measurements in
frequency range 80 – 1100 GHz and magnetic field of magnitude up to 16 T, to achieve high spectral
resolution. A pre-processing of measured signals by a dedicated digital signal processor will greatly
decrease the time of a final processing. Furthermore, we are developing a new design of a carousel
sample holder, which will be able to carry up to six samples in cryostat chamber at once.
All these features will enable faster and more exact experimental measurements. Our new
spectrometer will be useful in the investigation of spin relaxation times and spin-related quantum
phenomena, which understanding is necessary for the development of modern materials and
compounds.
Acknowledgement
„This project has received funding from the ERC under the European Union´s Horizon
2020 research and innovation programme, GA No.714850.“
[1] WEIL, John A. a James R. BOLTON. Electron paramagnetic resonance: elementary theory and practical
applications. 2nd ed. Hoboken, N.J.: Wiley-Interscience, c2007. ISBN 978-0471-75496-1.
[2] P. Neugebauer, A.-L. Barra. New Cavity Design for Broad-Band Quasi-Optical HF-EPR Spectroscopy.
Appl. Magn. Reson, 37, 833 (2010).
[3] J. W. Stoner, D. Szymanski, S. S. Eaton, et al. Direct-detected rapid-scan EPR at 250 MHz, J. Magn.
Reson. 170, 127 (2004).
Poster 35
NMR insight into nanopesticide bioavailability
O. Yu. Selyutina1, S. S. Khalikov
2, N. E. Polyakov
1,
1Russia, Novosibirsk, Voevodsky Institute of Chemical Kinetics and Combustion of SB
RAS
2Russia, Moscow,Nesmeyanov Institute of Organoelement Compounds of RAS
Scientific supervisor: Prof. N. E. Polyakov
To improve the bioavailability of plant protection compounds we used an approach based on the
non-covalent binding of natural water-soluble polysaccharides and oligosaccharides as delivery
systems. This approach is widely used in the pharmaceutical industry to develop new drugs with
increased solubility and bioavailability. The complexation of various plant protection compounds
(antidotes to herbicides: naphthalic anhydride and floroksam; pesticides: tebuconazole, imidacloprid,
imazalil and prochloraz) with natural poly- and oligosaccharides (arabinogalactan, glycyrrhizic acid,
sodium salt of carboxymethyl cellulose) have been studied by NMR relaxation technique. It was
demonstrated the solubility enchancement of plant protection compounds in the complexes under
study. The influence of delivery systems on penetration efficacy of plant protection products into
wheat, barley, rapeseed and corn seeds was also investigated by NMR methods. A significant
improvement in the penetration of the active components in the presence of complexants (0.1-1%) was
found. Such effect was also observed when arabinogalactan and glycyrrhizic acid were added in
standard patented composition for grains treatment. To understand the mechanism of this effect at
molecular level, the influence of polysaccharides and oligosaccharides on artificial lipid membrane
was studied by NMR relaxation method. It was concluded that the effect of polysaccharides and
oligosaccharides on the penetration efficacy of plant protection products might be associated with the
detected solubility enhancement and the affinity of delivery systems to the surface of cell membranes.
The development of new effective and safe preparations to protect plants from pests that increase
yield will reduce effective doses of active substances and reduce the negative impact on soil and the
ecosystem as a whole.
Acknowledgements
The reported research was funded by Russian Foundation for Basic Research, grant №18-416-
540007, 15-29-05792
Poster 36
The application of immobilized iridium complexes for the
generation of parahydrogen induced hyperpolarization
Ivan V. Skovpin1, Vladimir V. Zhivonitko
1 Laboratory of Magnetic Resonance Microimaging, International Tomography Center
SB RAS, Novosibirsk, Russia
2 NMR Research Unit, University of Oulu, P.O. Oulu, Finland
Low sensitivity is the main drawback of methods based on the phenomenon of nuclear magnetic
resonance (NMR spectroscopy and MRI). Last decades, approaches are actively developing aimed at
increasing sensitivity by creating a non-equilibrium spin polarization – hyperpolarization.
Parahydrogen induced hyperpolarization or PHIP is one such of the methods [1]. It is based on the use
of parahydrogen in hydrogenation reactions to create non-equilibrium populated systems. It is
important that the catalyst, which provides the activation and transfer of parahydrogen, is required for
the appearance of PHIP.
In this work we used immobilized catalysts based on neutral and cationic complexes of iridium
(Ir(COD)Cl2, [Ir(COD)Py2][PF6]). These compounds were grafted to the surface of phosphine-
modified silica gel and to Al2O3 by using heteropolyacids H3PW12O40, H4SiW12O40. Propyne, propene,
phenylacetylene and styrene were used as substrates in gas and liquid-phase hydrogenation,
respectively. It was found that the gas-phase hydrogenation of propyne by parahydrogen leads to the
observation of intense signals of PHIP on propene, a product of single hydrogen addition. The greatest
enhancement of the NMR signal of propene was about 800. At the same time, despite the active
hydrogenation of propene to propane, the signals of the PHIP were either not observed or were
comparable to the signals of thermal polarization. Similar results occurred when liquid-phase
hydrogenation of phenylacetylene and styrene was carried out. Thus, hydrogenation of the substrates
with triple carbon-carbon bond provides the greatest effect of PHIP. We assume that the
hydrogenation of the double bond is complicated by the exchange processes, which lead to loss of the
initial correlation of parahydrogen, reducing or completely eliminating the appearance of PHIP.
Acknowledgements. Ivan V. Skovpin thanks RFBR (16-33-60198) for financial support of the
research.
[1] C.R. Bowers. Encyclopedia of nuclear magnetic resonance, New York: John Wiley@Sons, 2002, 7,
750-770.
Poster 37
Terahertz Magnetic Resonance Spectrometer for Electron Spin
Dynamics Investigations
Antonín Sojka1, [email protected]
1Central European Institute of Technology, Brno, Czech Republic
Ing. Petr Neugebauer, Ph.D.
Magnetic resonance spectroscopy is a very powerful method in scientific research and it is well
known to the general public because of its common diagnostic application in hospitals (Magnetic
Resonance Imaging, MRI) [1]. During the last decades, a magnetic resonance method called High
Frequency Electron Paramagnetic Resonance (HFEPR) spectroscopy experienced a boom in the fields
of chemistry, biology, materials science, and physics [2], with commercially available spectrometers
allowing measurements at fixed frequencies and usually up to 263 GHz.
The aim of our work is to set up and develop a general purpose state-of-the-art broadband
Electron Paramagnetic Resonance spectrometer based on THz rapid frequency scans (ERC Starting
Grant THz-FRaScan-EPR) that will operate at frequencies between 80 GHz to 1100 GHz, at
temperatures from 1.8 K to 300 K, and at magnetic fields up to 16 T. High spectral resolution is
achieved by higher magnetic fields and higher frequencies, opening options to explore spin dynamics
and other phenomena not previously accessible by current technologies.
We present the design of a completely new concept of detection based on the rapid frequency
sweeps that allow performing spin relaxation investigations at THz frequencies, which are currently
either unexplored or undeveloped [3]. Fast sampling rate at several GS/s with high resolution will be
used to avoid missing details of the detected signal. Due to this fact, a large amount of data will be
gathered and processed in every measurement. Our novel design will allow multi-frequency relaxation
studies of a variety of samples ranging from bulk (crystal) materials, over powdered samples to air
sensitive samples in liquid solutions. Additionally, we are creating a new concept of carousel sample
holder that allows placing up to 6 samples at once inside the cryostat. User-friendly remote control of
the carousel will enable switching between samples without heating the cryostat, decreasing the
measurement time. Our approach will stimulate the development of new materials as well as lead to
the development of new MRI applications using HFEPR via Dynamic Nuclear Polarization (DNP)
measurements.
Acknowledgement: This project has received funding from the ERC under the European Union´s
Horizon 2020 research and innovation program, GA No.714850.
[1] K. Mobius, A. Savisky. High-Field EPR Spectroscopy on Proteins and their Model Systems:
Characterization of Transient Paramagnetic States, The Royal Society of Chemistry, (2009).
[2] P. Neugebauer, A.-L. Barra. New Cavity Design for Broad-Band Quasi-Optical HF-EPR Spectroscopy.
Appl. Magn. Reson, 37, 833 (2010).
[3] J. W. Stoner, D. Szymanski, S. S. Eaton, et al. Direct-detected rapid-scan EPR at 250 MHz, J. Magn.
Reson. 170, 127 (2004).
Poster 38
Magneto-optical studies of two-dimensional materials using
THz Electron Spin Resonance
A. Solodovnyk1*
, X. Zhang1, P. Neugebauer
1
1 Central European Institute of Technology, Brno University of Technology, Brno, Czech
Republic.
Ing. Petr Neugebauer, Ph.D.
Transition metal dichalcogenides (TMDs) figure among the most promising 2D materials and
candidates for the next generation of 2D electronics, flexible electronics, spintronics [1](eg, MoS2
[2]). Unlike their three-dimensional counterparts, which are semiconductors with an indirect band gap,
single layered TMDs usually have a direct band gap [3]. Electron spin resonance (ESR) can detect
resonant absorption of electromagnetic radiation corresponding to transitions between levels of
electron spin states, caused by internal effects and/or an applied external magnetic field. The strength
of such interactions in materials can range from tens of MHz to tens of THz. That is why the extension
of the ESR frequency range to higher values is one of the main challenges of modern ESR
spectroscopy nowadays.
We propose to apply THz-ESR to investigate solid-state samples such as TMDs in order to
reveal their magneto-optical properties. The emphasis will be put on bulk single-crystal TMDs as well
as on thin films of TMDs all the way down to a monolayer.
[1] Kośmider, K. J.; González, W. and Fernández-Rossier, J. Large spin splitting in the conduction band of
transition metal dichalcogenide monolayers. Phys. Rev. B 88, 245436, 2013;
[2] Sebenik, R. F. et al. Molybdenum and Molybdenum Compounds, Ullmann's Encyclopedia of Chemical
Technology. Wiley-VCH, Weinheim (2000);
[3] Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F. Atomically Thin MoS2: A New Direct-Gap
Semiconductor. Phys. Rev. Let. 105 (13), 2010;
Poster 39
EPR study of human serum albumin
Anna Spitsyna1,2,3
1 Novosibirsk State University, Novosibirsk 630090, Russia
2N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Novosibirsk
630090, Russia
3 International Tomography Center SB RAS, Novosibirsk 630090, Russia
Dr. Olesya Krumkacheva 1,3
Nanoscale distance measurements by pulse dipolar EPR spectroscopy (PDS) are increasingly
applied for gaining new insights into the structure and dynamics of complex biopolymers. PDS
provides the possibility of measuring long spin–spin distances of up to 16 nm. Most commonly, the
EPR distance measurements employ nitroxide spin labels. Recently the new type of spin labels based
on carbon-centered triarylmethyl radical (TAM) with improved properties was proposed. TAM labels
have microsecond relaxation times in solutions, narrow EPR spectra and high stability in various
biological reducing media. The disadvantage of TAM-based spin labels is related to their general
hydrophobicity which is the cause of exhibiting unwanted interactions with biomolecules and
aggregation.
In this work, to overcome the aggregation problem, a new hydrophilic TAM spin label has been
synthesized on the basis of Oxo63 radical. This new Oxo63 label has 12 polar hydroxyl groups
providing high water solubility. To study the properties of a new Oxo63 spin label it was selectively
introduced at Cys34 position of human serum albumin (HSA), which is an abundant plasma protein
with extraordinary ligand-binding properties. It was shown recently that HSA participates in amyloid
fibrils formation in cerebrum resulting in neurodegenerative diseases. The first stage of these
pathological process is the formation of HSA oligomers.
We have demonstrated that Oxo63 does not form aggregates with HSA and, being attached to the
protein, has the longest T2 relaxation time compared to nitroxide and Finland trityl. Furthermore,
PELDOR oscillations have been observed for singly spin-labeled HSA, that indicates the formation of
HSA oligomers in solution. The measured average interspin distance in HSA oligomers is about 2 nm
that indicates close contact between domains I of HSA within oligomers.
This work was supported by Russian Foundation for Basic Research N 18-04-00393
Poster 40
15N NMR and
15N MRI of high field SABRE hyperpolarized
molecules
Alexandra Svyatova1,2
, [email protected] 1International Tomography Center SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Dr. Kirill V. Kovtunov
The main disadvantage of nuclear magnetic resonance (NMR) is the low sensitivity because of a
small difference between the spin levels populations at the thermal equilibrium. Hyperpolarization
methods can significantly change population of spin levels and, as a result, NMR signal intensity can
be increased by several orders of magnitude.
For example, in Signal Amplification By Reversible Exchange (SABRE) approach [1] the
processes of p-H2 reversible exchange and ligands with It complex generate high levels of nuclear spin
polarization of an appropriate ligand. The SABRE process can be realized at both high magnetic field
(HF-SABRE) [2] and low magnetic field (conventional SABRE) [3]. In HF-SABRE experiments the
hyperpolarization is directly formed and detected in high magnetic field of NMR spectrometer. This
fact opens up opportunity to carry out in situ NMR and MRI experiments without magnetic field
cycling procedure.
To date, almost all MRI experiments are provided with the use of 1H atoms because of its high
gyromagnetic ratio and high natural abundance. However, the short lifetimes of hyperpolarized
molecules and high background signal in the experiments with living tissues limit an amount of
possible applications of SABRE. To solve this problem, polarization transfer from protons to other
nuclei (13
C, 15
N, 19
F, etc.) can be realized that, without doubt, expand the scope of biomolecules, which
potentially can be used as contrast agents in MRI.
In this work, 15
N-pyridine (15
N-py) was investigated by HF-SABRE approach. Several pulse
sequences were used to transfer polarization from bounced to the Ir complex atoms of p-H2 to 15
N
nuclei of 15
N-py. Optimization of pulse sequence parameters (offset and amplitude) and temperature
led to signal enhancement for 15
N-py up to 1100 and it was enough for 15
N MRI. The pulse sequence
for transferring polarization was integrated into conventional fast low angle shot (FLASH) MRI pulse
sequence for 15
N-py imaging. Previously, 15
N MR image time registration was higher than minutes. In
this work, for the first time the 15
N MR images were obtained in 2 seconds with one acquisition.
This work was supported by grant from RFBR #(16-03-00407-a)
[1] R. W. Adams, J Aguilar, K. D. Atkinson, M. J. Cowley, P. I. P. Elliott, S. B. Duckett, G. G. R. Green, I.
G. Khazal, J. López-Serrano, D. C. Williamson. - Science, 323, 1708–1711 (2009).
[2] D. A. Barskiy, K. V. Kovtunov, I. V. Koptyug, P. He, K. A Groome, Q. A. Best, F. Shi, B. M. Goodson,
R. V. Shchepin, A. M. Coffey, K.W.Waddell, E. Y. Chekmenev. - J. Am. Chem. Soc., 136, 3322–3325 (2014).
[3] K. V Kovtunov, L. M. Kovtunova, M. E. Gemeinhardt, A. V Bukhtiyarov, J. Gesiorski, V. I.
Bukhtiyarov, E. Y. Chekmenev, I. V Koptyug, B. Goodson. - Angew. Chemie Int. Ed.,56, 10433 –10437 (2017).
Poster 41
Mutational study of exposed hydrophobic groups in A42
fibril-catalyzed nucleation
Dev Thacker1 ([email protected])
1Lund University, Lund, Sweden.
Supervisor: Prof. Sara Snogerup Linse, PhD.
Alzheimer‘s disease is a neurodegenerative disease. The amyloid peptide A42 is involved in the
pathology of the AD. A42 is unfolded in its monomeric form, but has a high propensity to self-
assemble into highly ordered highly ordered amyloid fibrils. This process of A42 self-assembly from
monomeric to fibrillar aggregates involves a series of microscopic steps. The aggregation process
involves the formation of oligomers, which are believed to be the neurotoxic species. However, it is
not clear which residues are involved in the formation of A42 oligomers. The A42 fibril structure
solved by solid-state NMR shows the presence of two hydrophobic patches on the fibril surface1. It
can be reasoned that these hydrophobic patches are the regions where the oligomer formation is
initiated. We replaced these hydrophobic residues with serine to see whether the secondary nucleation
and hence the oligomer formation is affected in absence of the hydrophobic residues on the fibril
surface. We created serine mutants for the four hydrophobic residues on the fibril surface: V18S,
A21S, V40S, and A42S, two double-serine mutants for the two hydrophobic patches: V18S+A21S and
V40S+A42S, and one mutant where all the four hydrophobic residues were replaced with serine. The
aggregation kinetics was then studied for all these serine mutants using Thioflavin T fluorescence
assay.We performed aggregation assay and studied the kinetics for all the above stated serine mutants
of A42. We observed that the aggregation for all the mutants was dominated by secondary
nucleation. Hence it can be inferred that these hydrophobic patches on the fibril surface are not the site
of initiation of secondary nucleation. We also performed an ANS binding assay for the WT
Apeptide fibrils, and for the serine mutants, to confirm that there were no hydrophobic surfaces
present on the fibril surface of the mutants after replacing the four residues with serine. However,
ANS binding was observed with the mutant fibrils, indicating that there is in fact presence of
hydrophobic surfaces. This leads to the question: does amino acid mutation cause the protein to fold
differently? To confirm this, we might have to perform solid state NMR of the serine mutants and
compare the structure with the WT Afibril structure.
Simultaneously, we screen phage display libraries against A42 fibrils to select single chain
antibody fragments (scfvs) that are specific in binding to A42 fibrils. These antibody fragments will
be then purified and ranked according to their binding affinities by Surface Plasmon Resonance (SPR).
The highest binding scfvs will be then tested on A42 to study their effects on the aggregation
kinetics, secondary nucleation and its end‐ products, oligomers. Optimal conditions for imaging of
A42 fibrils for NMR will be determined and then titration of scfvs with A42 fibrils will be done to
gain further insight into the mechanism of the interaction between scfvs and A42 fibrils.
References:
[1] Atomic Resolution Structure of Monomorphic Aβ42 Amyloid Fibrils, Colvin MT, Silvers R, Ni
QZ, Can TV, Sergeyev I, Rosay M, Donovan KJ, Michael B, Wall J, Linse S, Griffin RG., J Am
Chem Soc. 2016 Aug 3;138(30):9663-74. doi: 10.1021/jacs.6b05129.
Poster 42
Ni(II)-complex formation and protonation states at the active-site
of a nickel superoxide dismutase-derived metallopeptide:
implications for the mechanism of superoxide degradation
Daniel Tietze,1* Alesia A. Tietze,2 Banabithi Koley Seth,1 Matthias Brauser,1 and Gerd Buntkowsky1*
1Eduard-Zintl Institute for Physical and Inorganic Chemistry, Darmstadt University of Technology, Alarich-
Weiss-Str. 8, 64287 Darmstadt, Germany
2Clemens-Schöpf Institute for Organic Chemistry and Biochemistry, Darmstadt University of Technology,
Alarich-Weiss-Str. 4, 64287 Darmstadt, Germany
A small, catalytically active metallopeptide (Nim6SOD, m
6SOD = ACDLAC), which was derived
from the nickel superoxide dismutase (NiSOD) active site was employed to study the mechanism of
superoxide degradation especially focusing on the protonation states of the Ni(II) donor atoms, proton
source and the role of the N-terminal proton(s). Therefore, we studied the Ni(II)-metallopeptide at
various pH and temperature using UV-Vis and NMR spectroscopy. These studies indicate a strong
reduction of the pKa of the Ni(II)-ligating donor atoms resulting in a fully deprotonated Ni(II)-active
site environment. Further, no titratable proton could be observed within a pH ranging from 6.5 to 10.5.
This rules out a recently discussed adiabatic proton tunneling-like hydrogen atom transfer process for
the metallopeptides, not found in the native enzyme.[1]
Furthermore, variable temperature 1H NMR
measurements uncovered an extended hydrogen bond network within the Ni(II) active site of the
metallopeptide similar to the enzyme.
With respect to the deprotonated Ni(II)-active site, the residual N-terminal proton, which is a
prerequisite for catalytic activity, cannot act as proton source. Most likely, it stabilizes the Ni(II)-
coordinated substrate in an end-on fashion thus allowing for an inner-sphere electron transfer.[2]
Lastly
and unlike the enzyme, the catalytic rate constant of superoxide degradation by the metallopeptides
was determined to be strongly pH dependent suggesting bulk water to be directly involved in proton
donation, which in turn strongly suggests the N-terminal histidine to be the respective proton donor in
the enzyme.[3]
Figure 1: Ni(II) active site protonation and mechanism of superoxide degradation revealed by NMR
spectroscopy and stopped-flow kinetics.
References
[1] a) J. Shearer, J. C. Schmitt and H. S. Clewett, J. Phys. Chem. B 2015, 119, 5453-5461; b) J. Shearer, K. L.
Peck, J. C. Schmitt and K. P. Neupane, J. Am. Chem. Soc. 2014, 136, 16009-16022; c) J. Shearer, Angew. Chem.,
Int. Ed. Engl. 2013, 52, 2569-2572.
[2] D. Nakane, Y. Wasada-Tsutsui, Y. Funahashi, T. Hatanaka, T. Ozawa and H. Masuda, Inorg. Chem. 2014,
53, 6512-6523.
[3] P. A. Bryngelson, S. E. Arobo, J. L. Pinkham, D. E. Cabelli and M. J. Maroney, J. Am. Chem. Soc. 2004,
126, 460-461.
Poster 43
Fullerene-based spin labels for dipolar EPR
spectroscopy
Ivan Timofeev1,2
1International Tomography Center SB RAS, 630090, Russia, Novosibirsk, 3a Institutskaya
str.
2Novosibirsk State University, 630090, Russia, Novosibirsk, 2 Pirogova str.
Dr. Olesya Krumkacheva1,2
Pulse dipolar EPR spectroscopy, mostly represented by pulsed electron-electron double resonance
(PELDOR/DEER), is widely applied tool for structural studies of proteins, nucleic acids and their
complexes. It allows distance measurements in the 1.5–8 nm range between spin labels site-
specifically introduced into a macromolecule of interest. Typical spin labels are nitroxide radicals.
Experiments employing nitroxide labels necessitate no less than 10-5
M concentration of spin-labeled
biomolecules, however, some biological systems such as ribosomal complexes can aggregate at this
concentration. To address the problem EPR laboratories are searching for new spin label kinds having
more intense EPR signal compared to nitroxide at the same concentration. Recently, Di Valentin, et al.
demonstrated the feasibility of distance measurements between
photoexcited porphyrin triplet state and nitroxide radical applying
PELDOR at 20 K [1]. The experiment exhibited high observed EPR
signal due to electron polarization of the photoexcited triplet state.
In this work, we propose to use photoexcited fullerene triplet state as
a new spin label for pulse dipolar EPR spectroscopy. Compared to
porphyrin, fullerene features 4 times narrower EPR line and relaxation
properties allowing pulse EPR detection up to room temperatures. To
implement PELDOR we synthesized model covalent pairs of fullerene
with spironitroxide (С60-NO•) and trityl (С60-Tr
•) radicals having long
phase relaxation times at room temperature. We studied relaxation time temperature dependences of
fullerene and its stable partners and obtained PELDOR time traces for both pairs in toluene at 80 K
and for С60-Tr• in o-terphenyl at 234 K.
С60-NO• gives PELDOR 80 K signal of the same 30% modulation depth and of higher sensitivity
compared to signal by the porphyrin-nitroxide pair at 20 K [1]. We managed to increase the observed
modulation depth to 70% using a trityl radical as a fullerene partner. С60-Tr• pair exhibits the most
optimal properties for pulse dipolar spectroscopy such as high signal to noise ratio, 70% modulation
depth and relaxation parameters suitable for room temperature PELDOR measurements.
This work was supported by RF President Grant 14.Y30.17.3214-MK
[1] M. Di Valentin M. Albertini, E. Zurlo, M. Gobbo, and D. Carbonera, J. Am. Chem. Soc., 2014, 136,
6582-6585
С60-NO•
С60-Tr•
Poster 44
Antioxidant and pro-oxidant activity of chelators in lipid membranes peroxidation
Viktor Timoshnikov1,2
, Olga Selyutina1, Nikolay Polyakov
1, George
Kontoghiorges3
1Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia
2Novosibirsk State University,Novosibirsk, Russia
3Postgraduate Research Institute of Science, Technology, Environment and Medicine,
Limassol, Cyprus
Scientific advisor: NikolayPolyakov, PhD
It is known that the cell membrane performs important functions, such as barrier, transport,
receptor and others. The main component of the membrane is the lipid bilayer. Most of the lipids
belong to phospholipids, consisting of a hydrophilic head and a hydrophobic tail.
In normal conditions, the cell membrane performs the above functions well. However, there are
diseases and pathologies, during which the active oxygen radicals (AOR) are being uncontrollably
generated. These radicals are able to react with all kinds of biomolecules, including phospholipids,
oxidizing and destroying them. As a result, oxidized lipids change the structure of the membrane,
affecting its properties [1].
The reasons of uncontrolled generation of AORs are numerous, for example, the accumulation of
metal ions in the body involved in redox reactions. The solution of this problem is the use of chelators.
These substances can bind to metal ions and remove them from the body. Chelators, used to treat
diseases associated with excess metals in the body, should have antioxidant properties, i.e. bind metal
ions not allowing them to participate in redox reactions. However, some chelators used as anti-cancer
drugs can have pro-oxidant activity, enhancing the generation of AOR in cancer cells, killing them [2].
There are many studies on the effect of chelators on the oxidation of cell membranes, but the
detailmechanisms haven‘t been found out.
In the present study the effect of chelators deferiprone and emodine on lipid peroxidation by iron
and copper ions was investigated by NMR method. Linoleic acid, capable of forming micelles in
aqueous solutions, was chosen as a model lipid. It was shown that deferiprone has more strong effect
on lipid peroxidation than emodine.
The reported research was funded by Russian Foundation for Basic Research, grant №18-34-
00343
[1] Jurkiewicz P, Olżyńska A, Cwiklik L, Conte E, Jungwirth P, Megli FM, Hof M., Biophysics of lipid
bilayers containing oxidatively modified phospholipids: insights from fluorescence and EPR experiments and
from MD simulations. BiochimBiophysActa. 2012, 1818(10): 2388-2402.
[2] D.S. Kalinowski, D.R. Richardson. The Evolution of Iron Chelators for the Treatment of Iron Overload
Disease and Cancer.Pharmacol.Rev. 57:547–583, 2005.
Poster 45
Geometries and energies of NHN hydrogen bonds:
spectral NMR diagnostic
Elena Tupikina1, [email protected]
1Faculty of Physics, St. Petersburg State University
Uljanovskaja 1, 198504 St. Petersburg, Russia
Supervisor Assoc. Prof. Dr. Peter M. Tolstoy
This work is dedicated to investigation of energetic and geometry characteristics of inter- and
intramolecular NH···N hydrogen bonds. As the model hydrogen bond donor we chose aniline
molecule, as the model hydrogen bond acceptor – various nitrogen bases.
We observed existence of linear correlation between hydrogen bond energy (computed both
directly and indirectly) and the difference of NMR chemical shifts of NH2 protons and propose
empirical correlation equations.
In order obtain the correlation we performed a series of calculations. The strengthening of the
NH···N hydrogen bond was modelled by the shortening of the N…N distance Calculations performed
at m062x/aug-cc-pVTZ level.
Acknowledgements this work was supported by RSF grant number 18-13-00050.
Poster 46
Paramagnetic properties of calcium aluminate C12A7
electrides coated by a thin carbon shell
Mikhail N. Uvarov1,2
1 Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya str., 3,
Novosibirsk, Russia
2 Boreskov Institute of Catalysis SB RAS, Lavrentiev Ave., 5, Novosibirsk, Russia
Alexander M. Volodin, professor
Calcium aluminate with 12CaO·7Al2O3 stoichiometry (C12A7) is the only currently known
inorganic material capable to form an electride state. Electrides are materials where electrons act as
anions [1]. Earlier it was demonstrated [2] that paramagnetic sites in inorganic core-shell structures
C12A7@C where carbon acts as a shell are characterized by narrower EPR signals in comparison with
bulk C12A7 at the same spin concentration. The main aim of this study was to analyze parameters of
paramagnetic sites in such samples by techniques of continuous wave and pulse EPR spectroscopy and
compare obtained features with those of well-known LiF:Li standard [3].
The X-band EPR line of C12A7@C has Lorenzian broadening with Hpp = 0.9 G at room
temperature and g = 1.9943. Remarkably, the EPR line became narrower with temperature decrease
down to liquid nitrogen temperatures, and the EPR line broadening is governed by phase relaxation.
Note that the stable EPR standard LiF:Li has a single narrow line which could be applied in the
temperature region within 6 K – 400 K [4]. Therefore C12A7@C could be one of EPR standards
which are necessary for precise characterization of paramagnetic species to measure g-tensor values
and number of spins. EPR investigations of modern materials based on C12A7@C could characterize
possible features of their electronic structures. Such information promises to be interesting to develop
some applications of electrides.
Acknowledgements
This study was supported by Russian Science Foundation, Project 16-13-10168.
[1] S. Matsuishi, Y. Toda, M. Miyakawa, K. Hayashi, T. Kamiya, M. Hirano, I. Tanaka, and H. Hosono,
Science, 301, 626 (2003)
[2] Volodin A.M., Zaikovskii V.I., Kenzhin R.M., Bedilo A.F., Mishakov I.V., Vedyagin A.A. Materials
Letters 189, 210 (2017)
[3] Eaton G.R., Eaton S.S., Barr D.P., Weber R.T. Quantitive EPR. Springer, 2010.
[4] Cherkasov F.G., Ovchinnikov I. V., Turanov A. N., L‘vov S. G., Goncharov V. A. Low Temperature
Physics 23, 174 (1997)
Poster 47
EPR investigations of float soda-lime glass as a retrospective
dosimeter
Maja Vojnić Kortmiš1, [email protected]
1Department of Occupational Safety and Health, Fire and Radiation Protection, Ruđer
Bošković Institute, Bijenička cesta 54, Zagreb, Croatia
Assoc. prof. dr. sc. Nadica Maltar-Strmečki
In this research project we are investigating electron paramagnetic resonance (EPR) dosimetry of
transparent float soda-lime glass in the dose range below 20 Gy for retrospective dosimetry purposes.
Since it is easily found in the places of nuclear and radiological mass-casualty incidents and possible
terrorist events involving the dispersal of radioactive materials, it is useful for retrospective dosimetry.
Previous investigations of glasses demonstrated good behavior of soda-lime glass as a
retrospective dosimeter but mostly in the high dose range. The detection in the dose range from 0-8 Gy
is essential regarding the medical treatment of casualties, to discriminate the acute radiation syndrome
treatment from long-term surveillance within a clinically relevant time period. Medical treatment of
radiological casualties depends on the received doses According to the literature the casualties whose
radiation dose is most amenable to treatment will be those who receive between 2 and 6 Gy.
It is well known that low dose limit in EPR dosimetry of glasses is dependent on the background
signal. The background signal (BKS) of the soda-lime glass is competing with the radiation induced
signal (RIS) for the doses below 6 Gy. According to previous research the BKS can be attributed to
transition-group ions, ferromagnetic precipitates, photo-induced centers as well as mechanical induced
defects. The calibration dose-EPR intensity curve of float soda – lime glass in the low dose regime
gives inaccurate answer of the unknown dose.
In this research project we are investigating other physical parameters at low dose regime that
influence EPR spectrum and that could increase sensitivity of dose reading in low dose range.
Acknowledgements: This work has been partly supported by Croatian Science Foundation under
the project number 1108 ‗‗Low-temperature molecular dynamics of systems exhibiting disorder
probed by ESR‘‘.
[1] Bassinet, C.; Trompier, F.; Clairand, I. Health Phys. 2010, 98, 400-405.
[2] Koenig, K. L.; Goans, R. E.; Hatchett, R. J.; Mettler, F. A.; Schumacher, T. A.; Noji, E. K.; Jarrett, D.
G. Ann. Emerg. Med. 2005, 45, 643-652.
[3] Gancheva, V.; Yordanov, N. D.; Karakirova, Y. Spectr. Acta. A. 2006, 63, 875-878.
[4] Ainsbury, E. A.; Samaga, D.; Della Monaca, S.; Marrale, M.; Bassinet, C.; Burbidge, I. C.; Correcher,
V.; Discher, M.; Eakins, J.; Fattibene, P.; Güçlü, I.; Higueras, M.; Lund, E.; Maltar-Strmečki, N.; McKeever, S.;
Rääf, L. C.; Sholom, S.; Veronese, I.; Wieser, A.; Woda, C.; Trompier, F. Radiat. Prot. Dosim. 2017, 178(4),
382-404.
Poster 48
Investigation of blue-light photoreceptors using CIDNP
Jakob Wörner1, [email protected]
1Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg,
Germany
Prof. Dr. Stefan Weber
Blue-light receptors, such as blue-light sensing using flavin (BLUF)-domains, cryptochromes
(cry) and light-oxygen-voltage (LOV)-domains, can be found in almost all organisms as blue-light can
induce significant damage to most matter. They often feature a flavin or any of its derivates as their
cofactor and their reaction upon illumination follows a common scheme: Light illumination induces
the formation of a radical pair that is formed by the chromophore and a proximate amino acid
followed by a subsequent reactions that trigger the biological response(s) of the respective protein [1].
As all of these subsequent reactions share a common step, the formation of a radical pair, they can
be probed by chemically induced dynamic nuclear polarization (CIDNP) spectroscopy. CIDNP
spectroscopy is a form of nuclear magnetic resonance (NMR) spectroscopy and exploits the
polarization transfer from the electrons towards the nuclei for the lifetime of the radical pair [2].
Using the CIDNP effect has two main advantages: On the one hand the CIDNP effect can result in
massive signal enhancement. On the other hand, CIDNP spectra can be used to extract magnetic
resonance parameters of very short-lived radical pairs that are undetectable by electronic paramagnetic
resonance (EPR) [3].
The focus of my PhD are mutated LOV domains and reconstituted LOV domains. Mutating the
LOV domains can massively prolong the lifetime of the radical pair and enhances its CIDNP effect
[4]. Also, reconstituting the flavin by its derivatives opens up the means to alter the optical and kinetic
parameters of LOV domains.
[1] A. Losi, W. Gärtner, Annu. Rev. Plant Biol.2012, 63, 49–72.
[2] J. Bargon, H. Fischer, Z. Naturfors. Sect. A-J. Phys. Sci.1967, 22, 1151–1555.
[3] A. S. Kiryutin, O. B. Morozova, L. T. Kuhn, A. V. Yurkovskaya, P. J. Hore, J. Phys. Chem. B2007,
111, 11221–11227.
[4] G. Richter, S. Weber, W. Römisch, A. Bacher, M. Fischer, W. Eisenreich, J. Am. Chem. Soc.2005,
127, 17245–17252.
Poster 49
Time-resolved and field-dependent CIDNP study of
photoreaction of flavin adenine dinucleotide with tryptophan:
intramolecular and intermolecular electron transfer
Ivan V. Zhukov1,2
1ITC SB RAS, Novosibirsk, Russian Federation,
2Novosibirsk State University, Novosibirsk, Russian Federation
Supervisor: Dr. Aleksandra V. Yurkovskaya
Flavin Adenine Dinucleotide (FAD) is an important cofactor in flavoproteins, which have
been proposed as magnetoreceptors in many biologically relevant reactions e.g. in migratory bird
navigation or in phototropism. Upon light illumination, in the cyclic reaction of intramolecular
electron transfer (ET) from Adenine to Flavin a short-lived biradical (BR) with the reduced flavin and
oxidized adenine moieties primarily forms. Magnetic interaction such as hyperfine and exchange
interactions are important for the magnetic field sensitivity of photoreaction of FAD. At the presence
of tryptophan (Trp), an electron is transferred from Trp to the adenine cation radical moiety of the
transient FAD biradical leading to the formation of a secondary pair consisting of the Flavin anion and
tryptophanyl cation radicals (RP). The back electron transfer rate is sensitive to the external magnetic
field strength, while the magnetic field dependence of the overall reaction yield is given by the
superposition of contributions from both primary biradical and secondary radical pair stages. A central
aim of our study was determination of the role of exchange interaction in FAD biradicals. Two
consecutive steps in light-induced processes have to be analyzed. As observables, we use chemically
induced dynamic nuclear polarization (CIDNP). The hyperpolarization formed is sensitive to magnetic
resonance parameters of the radicals such as g-factors, hyperfine coupling constants, exchange
interaction, and other. For disentanglement of the contributions from intramolecular and
intermolecular electron transfer, we use three systems: pure FAD, FAD plus Trp, and flavin
mononucleotide (FNM) plus Trp. They proceed via intramolecular ET with biradical intermediate;
combined intra- and intermolecular ET forming biradical and RP, and exclusively via intermolecular
ET with only RP intermediates, respectively. From the time dependence of CIDNP we can separate
the geminate processes in BRs and in free RPs, while from the magnetic field dependence we get
value and sign of exchange interaction (J-coupling) in the transient BRs. These observations show that
the spin dynamics in the primary FAD biradical has to be taken into account when considering the
magnetoreception mechanism of the photoreaction between FAD and Trp. Thus, CIDNP is a valuable
alternative technique for analyzing magnetic interactions in transient radicals and biradical, in
particular when EPR and optics alone are not sensitive enough.
Poster 50
Light-induced charge separation at organic donor/acceptor
composite
E.A.Beletskaya1,2
,D.A. Nevostruev2, L.V. Kulik
2
1Novosibirsk state university, Faculty of natural science
2Voevodsky Institute of Chemical Kinetics and Combustionof Siberian Branch of RAS,
email: [email protected]
Of all the known ways of using solar energy, the most effective is photoelectric.
Nowadays inorganic substances such as silicon are mainly used in solar photocells. These
photocells are expensive, therefore today attention is paid to organic photovoltaics.
The active layer of organic solar cells usually comprises a semiconducting polymer and a
fullerene derivative (C60). In this mixture the polymer acts as the donorfrom which the
photoexcited electron is transferred to the acceptor (fullerene). Thus, the charge transfer (CT)
state is formed. Charges of different sign then move to the electrodes: electrons through
acceptor molecules, and holes through polymer chains.Time-resolved EPR experiments have
shown that the CT state is a spin-correlated radical pair.
A powerful tool for investigating spin-correlated radical pairs is out-of-phase electron
spin echo spectroscopy. Using this method, one can determine distance between charges at a
certaintimeafter CT state generation by laser pulse.It is possible to make conclusions about
the degree of separation of charges from these data.
In this work, light-induced out-of-phase ESE signal is registeredfor the composite
PCDTBT/PC70BM.Dependence of the out-of-phase echo intensity on the delay between the
microwave pulses is studied. The average initial distance between electron and hole in CT
state 5 nm (T=80K) and distance distribution G(r)= exp[-(r-4,5)2 /4] is determined.
Recombination of CT statePCDTBT+/PC70BM
˗ via singlet channel has characteristic rate
constant 1,7*104 s
-1. Recombination via triplet channel is much slower.
Kraffert, F., &Behrends, J. Molecular Physics,2017,115(19); 2373-2386.
Lukina E. A., Popov A. A., Uvarov M. N., Kulik L. V., J. Phys. Chem.,2015, 119;13543–13548.
Poster 51
Development of a Sensitive Setup for Measuring the Hall Effect
in low-Mobility Materials
Ilia Kulikov1, e-mail: [email protected]
1Freie Universität Berlin, Germany
Supervisor: Prof. Dr. Jan Behrends
Charge transport in organic semiconductors strongly depends on two parameters: charge carrier
concentration and charge carrier mobility [1]. While the concentration of charge carriers can
conveniently be determined by quantitative EPR spectroscopy, the mobility is usually measured using
complementary experimental techniques [2].
Here we report on the development of
a highly sensitive AC Hall effect setup [3]
for measuring charge carrier mobilities in
organic semiconductors. The signal-to-
noise ratio has been improved
significantly by modulating both the
magnetic field (from -1 to 1 T at a
frequency of up to 100 Hz) as well as the
current through the sample. The Hall
voltage is detected at the difference
frequency. This scheme allows us to
separate the Hall voltage from Johnson
noise, probe misalignment voltage and thermoelectric voltage. The setup was compared to
conventional DC Hall effect measurements using n- and p-doped silicon samples. The improved
sensitivity of the setup allows for measuring charge carrier mobilities in the range of 10-6
cm2 V
-1 s
-1,
which is six orders of magnitude below the resolution of a conventional Hall setup.Measurements of
hole mobilities in low-mobility organic semiconductors demonstrate the high sensitivity of the setup:
charge carrier mobilities of 10-5
cm2 V
-1 s
-1 were confidently observed. We will discuss how this setup
can be used to characterize semiconducting polymers with applications in solar cells.
[1] A. J. Heeger, Semiconducting and Metallic Polymers: The Fourth Generation of Polymeric Materials
(Nobel Lecture), The Journal of Physical Chemistry B 1 (4-5) (2001) 247–267. doi:10.1016/S1567-
1739(01)00053-0.
[2] S. Tiwari, N. C. Greenham, Charge Mobility Measurement Techniques in Organic Semiconductors,
Optical and Quantum Electronics 41 (2) (2009) 69–89. doi:10.1007/s11082-009-9323-0.
[3] A. M. Hermann, J. S. Ham, Apparatus for the measurement of the hall effect in semiconductors of low
mobility and high resistivity, Review of Scientific Instruments 36 (11) (1965) 1553–1555. doi:10.1063/1.1719390
Poster 52
Proton dependence of time resolved magnetic field effect
spectra (TRMARY) in the intramolecular electron transfer
reaction of FAD
Akihiro Sakashita1, [email protected]
1Graduate School of Science and Engineering, Saitama University, Saitama, Japan
Prof. Kiminori Maeda1
【 Introduction】 Flavin Adenine Dinucleotide(FAD) is one of the
most important coenzymes in the biological systems. Previously,
Kaptein et al. observed the photo-CIDNP signal and proposed the
biradical formation by intramolecular electron transfer reaction from
the triplet excited states.[1,2] Afterward, Murakami, Maeda et al.
studied Magnetic Field Effect (MFE) on transient absorption (TA) in
laser flash photolysis. In this, the inter-conversion between the radical
pair (RP) and the triplet excited state (T) of the flavin part was
discovered and that strongly depends on the proton concentration, pH
[3]The kinetic feature has been discussed well. However, the spin
dynamics of the RP has not been discussed for long time because it is
difficult to obtain high quality data of time resolved Magnetically
Affected Reaction Yield (TRMARY) spectra. Recently, we have newly
developed a custom-made TA setup for the stable measurement of the
TRMARY spectra [4]. In the process, we could use less fluctuating
pump and probe lasers in addition with improvement of the sensitivity.
The time evolution of the half width half maximum (B1/2) of TRMARY
is determined and discussed in different pH conditions.
【 Results and Discussion】 The difference of the TA, A(B, t), which
is the TA in presence of the magnetic field A(B, t) minus that in
absence of the field A(0, t), is plotted in Fig.1at pH 3.5(a) and pH 2.0
(b). This two dimentional A(B, t) data is sliced in each delay after
the laser irradiation and fitted by Lorentz function. The obtained B1/2is
plotted versus the delay time as shown in Fig.2.The B1/2monotonously
increase with time. The theoretical calculation by Stochastic Liouville
equation predict that the increment of B1/2 is caused by the spin
dephasing and the net lifetime of RP state. The difference of the B1/2 in
different pH suggests the different spin dephasing dynamics. The detailed analysis is now underway.
References
[1] C. G.van Schagen, F. Müller, R. Kaptein, Biochemistry21, 402(1982).
[2] S. Stob,J. Kemmink, R. Kaptein, J. Am. Chem. Soc.111, 7036(1989).
[3] M. Murakami, K. Maeda, T. Arai, J. Phys. Chem. A109, 5793(2005).
[4]K.Arakawa et alAsia Pacific EPR/ESR symposium, IN-04, PO-02(2016)
Fig.2. Time evolution of B1/2in each pH
aqueous solution
Fig.1.2D-presentation of Magnetic
field effect on TA, A(B, t) at pH3.5(a)
and 2.0(b).
8.5
8.0
7.5
7.0
6.5
B1
/2/m
T
0.70.60.50.40.30.2
Time / µs
pH 2 pH 3.5