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Ulf Rørbæk Pedersen (RUC) Supervisors Dorthe Posselt (RUC) Peter Westh (RUC) Güenter Peters (DTU). The Structure of Phosphor Lipid Membranes Embedded with n-Alcohols Investigated by SAXS and MD-Simulations. Introduction. Method: Small angle x-ray scattering (SAXS)
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Ulf Rørbæk Pedersen (RUC) Supervisors Dorthe Posselt (RUC) Peter Westh (RUC) Güenter Peters (DTU) The Structure of Phosphor Lipid Membranes Embedded with n-Alcohols Investigated by SAXS and MD-Simulations
Introduction Method: • Small angle x-ray scattering (SAXS) • Molecular Dynamics Simulations (MD-simulations) System: DMPC/hexanol (MD-simulations) and similar systems (SAXS)
SAXS Model Smearing from line shaped beam in Kratky camera ( ) q = |kin - kout|
SAXS data DMPC DMPC/hexanol elektron dencity [a.u.] DMPC/hexanol DMPC
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)
Membrane area A=59.6 Ų (30˚C)
Voronoi Volumes mean voronoi volume [ų] number carbon in acyl chain VDMPC=1101 ų
Order parameter carbon number in acyl chain
Flip-flop event Dt = 0.4 ns
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)
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