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Weiche Materie Vortrag: Do., 09:40–10:00 D-V28
Using Neutron Spectroscopy to Study Collective Dynamics of Biological
and Model Membrane Systems
Maikel C. Rheinstädter 1 , Tilo Seydel 1 , Wolfgang Häussler 2 , Tim Salditt 3
1 Institut Laue-Langevin, B.P. 156, 6 rue Jules Horowitz, 38042 Grenoble, France –
2 FRM-II, Technische Universität München, 85747 Garching, Germany – 3 Institut für
Röntgenphysik, Friedrich-Hund Platz 1, 37077 Göttingen, Germany
While most spectroscopic techniques, as, e.g., nuclear magnetic resonance or dielectric
spectroscopy probe macroscopic responses, neutron and within some restrictions
also x-ray scattering experiments give the unique access to microscopic dynamics at
length scales of intermolecular or atomic distances. Only recently, it has become possible
to study collective dynamics of planar lipid bilayers using neutron spectroscopy
techniques [1]. We determined the dispersion relation of the coherent fast picosecond
density fluctuations on nearest neighbor distances of the phospholipid acyl chains in
the gel and in the fluid phases of a DMPC bilayer and could shed light on the evolution
of structure and dynamics in the range of the gel-fluid main phase transition. By
combining different neutron scattering techniques, namely three-axis, backscattering
and spin-echo spectroscopy, we present measurements of short and long wavelength
collective fluctuations in biomimetic and biological membranes in a large range in momentum
and energy transfer, covering time scales from about 0.1 ps to almost 1 µs and
length scales from 3 ˚A to about 0.1 µm [1-4]. Because of optimized setups and sample
preparation, inelastic neutron scattering experiments supply for the first time sufficiently
strong coherent inelastic signals for quantitative analysis. The measurements
offer a large window of length and time scales to test and refine theoretical models
of dynamics of biomimetic and biological membranes. From a smectic hydrodynamic
theory, the long wavelength dispersion relation give direct access to the elasticity parameters
of the membranes in the fluid phase [3], i.e., the bilayer bending rigidity κ
and the compressional modulus B of the stacks.
[1] M.C. Rheinstädter, C. Ollinger, G. Fragneto, F. Demmel, T. Salditt, Phys. Rev.
Lett. 93, 108107 (2004).
[2] Maikel C. Rheinstädter, Tilo Seydel, Franz Demmel, Tim Salditt, Phys. Rev. E
71, 061908 (2005).
[3] Maikel C. Rheinstädter, Wolfgang Häußler, Tim Salditt, submitted.
[4] Maikel C. Rheinstädter, Tilo Seydel, Tim Salditt, submitted.