1 influence of microhydration on the ionization energy thresholds of thymine university of southern...

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Influence of Microhydration on the Ionization

Energy Thresholds of Thymine

University of Southern CaliforniaDepartment of Chemistry

Kirill Khistyaev, Prof. Anna I. Krylov

NH

NH

O

O

64th OSU International Symposium on Molecular SpectroscopyJune 22-26, 2009

22

Importance of ionization processes Importance of ionization processes in DNAin DNA11

1Bernd Giese, Annu. Rev. Biochem. 2002. 71:51–70 DOI: 10.1146/annurev.biochem.71.083101.134037

33

Experimental dataExperimental data22. PIE curves.. PIE curves.

a. thymine

b. thymine−H2O

c. thymine−(H2O)2

d. thymine−(H2O)3

Photoionization efficiency (PIE) curves recorded for

2Leonid Belau, Kevin R. Wilson, Stephen R. Leone, and Musahid Ahmed, Vacuum-Ultraviolet Photoionization Studies of the Microhydration of DNA Bases (Guanine, Cytosine, Adenine, and Thymine), J. Phys. Chem. A 2007, 111, 7562-7568

44

Experimental results.Experimental results.

Appearance Energies of Four DNA Bases and Complexes with WaterAppearance Energies of Four DNA Bases and Complexes with Water

monomer monohydrate dihydrate trihydrate

thymine 8.90 ± 0.05 8.75 ± 0.05 8.6 ± 0.1 8.6 ± 0.1

adenine 8.30 ± 0.05 8.20 ± 0.05 8.1 ± 0.1

guanine 8.1 ± 0.1 8.0 ± 0.1 8.0 ± 0.1 8.0

cytosine 8.65 ± 0.05 8.45 ± 0.05 8.4 ± 0.1 8.3 ± 0.1

55

Theoretical studies. Theoretical studies. Thymine + HThymine + H22O tautomers.O tautomers.22

2Jaroslav Rejnek, Michal Hanus, Martin Kabela, Filip Ryjaek and Pavel Hobza,Phys, Chem. Chem. Phys . , 2005 , 7 , 2006–2017

66

Thymine + HThymine + H22O O

geometry optimization.geometry optimization.

1.351

1.378 1.386

1.215

1.383

1.405

1.219

1.4661.456

1.221

1.400

1.375

1.227

1.3711.372

1.352

1.017

1.006

0.001

-0.006 -0.016

-0.008

-0.005

0.002

-0.01

0.011

0.002

ThymineThymine + H2O

Δ

rimp2/ccPVTZ

77

Ionization Energies, eVIonization Energies, eV

A'' 9.01

(9.13 for Thymine)A' 10.10

(10.13)

A'' 10.51

(10.52)A' 11.10

(11.04)

Thymine + H2O

(Thymine)

EOM-CCSD/cc-PVTZ

ΔIE = 0.12 eV ΔIE = 0.03 eV

ΔIE = 0.01 eV ΔIE = -0.06 eV

88

Ionization Energies, eVIonization Energies, eVThymine + H2O

(Thymine) A'' 12.30

(12.39 for H2O)

A'' 12.53

(12.67 for Thymine)

A' 13.70

(13.82 for Thymine)

EOM-CCSD/cc-PVTZ

99

IE of Thymine at geometry of IE of Thymine at geometry of Thymine + HThymine + H22O clusterO cluster

IP of Thymine at the equilibrium geometry IP of Thymine at the equilibrium geometry is 9.13 eVis 9.13 eV

IP of Thymine at the equilibrium geometry IP of Thymine at the equilibrium geometry of Thymine + Hof Thymine + H22O complex is 9.16 eV O complex is 9.16 eV

ΔΔIP = 0.03 eV due to the geometry changeIP = 0.03 eV due to the geometry change

EOM-CCSD/cc-PVTZ

1010

Charge distribution.Charge distribution.First Ionization EnergyFirst Ionization Energy

Element # Nutral Ionized Δ

C 2 -0.190 0.066 0.256

N 4 -0.658 -0.456 0.202

O 9 -0.599 -0.437 0.162

O 10 -0.679 -0.504 0.175

O 16 -1.020 -1.026 -0.006

H 17 0.518 0.509 -0.009

H 18 0.500 0.527 0.027

∑H2O -0.002 0.009 0.011

0.256

0.202

0.162

0.175

ΔΔIP = 0.12 eVIP = 0.12 eV

0.011

NBO/EOM-CCSD/6-31+G(d)

1111

Charge distribution.Charge distribution.Second Ionization EnergySecond Ionization Energy


O 9 -0.599 -0.105 0.494

O 10 -0.679 -0.520 0.159

O 16 -1.020 -1.017 0.004

H 17 0.518 0.506 -0.012

H 18 0.500 0.522 0.022

∑H2O -0.002 0.011 0.013

0.494

0.159

ΔΔIP = 0.03 eVIP = 0.03 eV

0.013


1212

Charge distribution.Charge distribution.Third Ionization EnergyThird Ionization Energy


N 6 -0.301 -0.679 0.377

O 9 -0.336 -0.599 0.263

O 10 -0.418 -0.679 0.261O 16 -1.011 -1.020 0.009

H 17 0.500 0.518 -0.017

H 18 0.524 0.500 0.024

∑H2O -0.002 0.014 0.016

0.377

0.263

0.261

ΔΔIP = 0.01 eVIP = 0.01 eV

0.016


1313

Charge distribution.Charge distribution.Fourth Ionization EnergyFourth Ionization Energy


O 9 -0.336 -0.44-0.4488 0.150.1511

O 10 -0.418 -0.14-0.1488 0.5310.531O 16 -1.011 -0.98-0.9877 0.030.0344

H 17 0.501 0.4780.478 -0.0-0.04040

H 18 0.524 0.530.5344 0.030.0344

∑H2O -0.002 0.025 0.027

0.531

0.151

ΔΔIP = -0.06 eVIP = -0.06 eV

0.027


1414

Correlation between Correlation between ΔΔIE and cIE and charge transfer harge transfer between Hbetween H22O and ThymineO and Thymine

0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.028

-0.05

0.00

0.05

0.10

0.15

IE

, eV

Change of H2O charge, a.u.

1515

Charge-dipole interaction.Charge-dipole interaction.

-δ’

+δ’’

1616

Correlation between charge-dipole Correlation between charge-dipole interaction and ionization energy.interaction and ionization energy.

1.5 1.6 1.7 1.8 1.9 2.0 2.1

-0.05

0.00

0.05

0.10

0.15

IE

, eV

Charge-dipole interaction energy, eV

IE1

IE2

IE3

IE4

1717

Geometry of the first ionized stateGeometry of the first ionized state (omegaB97X-D/cc-pvtz)(omegaB97X-D/cc-pvtz)

1.456

1.221

1.400

1.375

1.227

1.3711.372

1.352

1.017 1.040

1.379

1.1921.369

1.288

1.338

1.408

1818

IE of different structures of IE of different structures of Thymine + HThymine + H22OO

1919


ThymineTh+H2O

t1ΔIE

Th+H2O t2

ΔIETh +H2O

t3ΔIE

9.13 9.01 0.12 9.05 0.08 9.08 0.05

10.13 10.1 0.03 10.17 -0.04 9.97 0.16

10.52 10.51 0.01 10.36 0.16 10.34 0.18

11.04 11.1 -0.06 10.87 0.17 11.03 0.01

12.39 12.3 0.09 12.58 -0.19 12.63 -0.24

12.67 12.53 0.14 11.94 0.73 11.97 0.7

13.82 13.7 0.12 13.6 0.22 13.55 0.27

13.84 13.76 0.08 13.78 0.06 13.67 0.17

2020


9 10 11 12 13 140

20

40

60

80

100

IE, eV

2121

Conclusions:Conclusions: First calculated IE of thymine + HFirst calculated IE of thymine + H22O cluster is 9.01 eV O cluster is 9.01 eV

which is 0.12 eV lower than IE of thymine.which is 0.12 eV lower than IE of thymine.

Charge distribution between thymine and water for the Charge distribution between thymine and water for the

fist 3 ionized states can’t explain change in IE.fist 3 ionized states can’t explain change in IE.

Geometry change can’t explain the difference in IP.Geometry change can’t explain the difference in IP.

Change in IE can be explained by charge-dipole Change in IE can be explained by charge-dipole

interaction between thymine and water molecule.interaction between thymine and water molecule.

Oxygen atom of water molecule stabilize a positive Oxygen atom of water molecule stabilize a positive

charge on nearest atomscharge on nearest atoms

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AcknowledgmentsAcknowledgments• Prof. Anna I. Krylov Prof. Anna I. Krylov

groupgroup• Dr. Ksenia BravayaDr. Ksenia Bravaya• iOpenShell center for iOpenShell center for

computational studiescomputational studies• QChem QChem ab initio ab initio

packagepackage

2323

Thank you for your attentionThank you for your attention

1 influence of microhydration on the ionization energy thresholds of thymine university of southern...

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