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Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P186
Water Dynamics in Phospholipid Model Membrane Systems
Sebastian Busch 1 , Fanni Juranyi 2,3 , Thomas Gutberlet 3
1 Physics Dept. E13, Technical University Munich, 85747 Garching, Germany –
2 Physical Chemistry, University of the Saarland, 66123 Saarbruecken, Germany – 3 Lab.
f. Neutron Scattering, PSI ETHZ, 5232 Villigen PSI, Switzerland
Biological membranes are characterized by a complex hierarchy of motions which is
a fundamental prerequisite for their functionality on nature. Hydration of phospholipid
bilayers and dynamics of water molecules at the membrane surfaces are of special
importance in this context. The dynamical behavior in such membranes exhibits correlation
times ranging from 10 −12 s with the motion of alkyl chain defects up to 1 s
corresponding to collective excitations of the bilayer. Due to the huge spread in correlation
time and length quite different experimental approaches have been employed
to study membrane dynamics ranging from light microscopy, dynamic light scattering,
NMR, ESR, QENS, NSE and MD simulations [1-5].
To understand the dynamic behavior of water molecules in phospholipid membrane
systems we have started to investigate the motions of water molecules in such systems
by quasielastic neutron scattering. Rotational and translational motions of water
molecules membrane bound and non-bound were described for phospholipids model
membranes of DPPC below the main phase transition from fluid to gel state at different
levels of low hydration [6]. Water diffusion constants below the bulk value of
water were reported. We have extended these studies to phospholipids membranes at
full hydration in the biological relevant fluid state. QENS measurements of alkyl chain
deuterated DMPC at full hydration at different temperatures above and below the main
phase transition were performed at the time-of-flight neutron spectrometer FOCUS at
SINQ/PSI. The results show water diffusion within the phospholipids membranes similar
to the diffusion of bulk water. The results and the corresponding measurements
will be presented and discussed.
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[4] S. Koenig et al., Biophys. J., 68 (1995) 1871.
[5] M.C. Rheinstaedter et al., Phys. Rev. Lett. 93 (2004) 108107.
[6] S. Koenig et al., J. Chem. Phys., 100 (1994) 3307.