the structure of phosphor lipid membranes embedded with n-alcohols investigated by saxs and...
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The Structure of Phosphor Lipid Membranes Embedded with
n-Alcohols Investigated by SAXS and MD-Simulations
Ulf Rørbæk Pedersen (RUC)
Supervisors
Dorthe Posselt (RUC)Peter Westh (RUC)
Güenter Peters (DTU)
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Introduction
Method:● Small angle x-ray scattering (SAXS)● Molecular Dynamics Simulations (MD-simulations)
System: DMPC/hexanol (MD-simulations)and similar systems (SAXS)
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SAXS Model
Smearing from line shaped beamin Kratky camera ( )
q = |kin - kout|
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SAXS data
DMPC/hexanolDMPC
DMPC
DMPC/hexanol
elek
tron
den
city
[a.
u.]
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SAXS data
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Molecular Dynamic Simulations
Program: NAMD
Force Field: CHARMM27
with modified charges in headgroup , RHF 6-31G*.
TIP3 water
Constant NPT, P=1 atm (Nosé-Hoover Langevin piston)
Periodic boundary conditions
Full electrostatics(Particle Mesh Ewald)
Time step: 1 fs(velocity Verlet integration method)
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Membrane area
A=59.6 Ų (30˚C)
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Density profile
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Voronoi Volumes
number carbon in acyl chain
mea
n vo
rono
i vol
ume
[ų]
VDMPC=1101 ų
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Order parameter
carbon number in acyl chain
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Flip-flop event
t = 0.4 ns
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Summary
Alcohol molecules intercalate with the hydroxy group in the hydrophilic part and the acyl chain parallel to
the fatty acids
n-hexanol in a membrane introduces● a reduction of the thickness (SAXS) ● a condensations of the area (MD)● a softer membrane (MD)● more free volume in inner part of membrane (MD)● more order in outer part of membrane (MD)● less order in inner part of membrane (MD)
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Perspectives
● How can we modify the properties of a membrane by doping?● Permeability● Concentration dependence● The dependence of alcohol length● Other doping molecules (cholesterol, other anesthesia)● MD-Pulling experiment
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Equations
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SAXS of MLV
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Distribution of Voronoi Volumes
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Density profile
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Literature