The understanding of dynamics and functioning of biological membranes and in particular of membrane embedded proteins is one of the most fundamental problems and challenges in modern biology and biophysics. Even though biological membranes were studied for decades, very few biologically relevant processes were revealed on a molecular level. The reason is the combination of very small nanometer length scales and very fast dynamics of pico- and nanoseconds, which poses particular experimental challenges. Neutron scattering is an ideal microscope to study structure and dynamics in these systems, because it gives access to the relevant length and time scales. New instrumentation and more powerful neutron sources offer greatly enhanced sensitivities and are capable to access a large range of time and length scales, covering microscopic to mesoscopic dynamics. The optimized intensity even allows to study dynamics in single bilayers.
We discuss how membrane properties, such as elasticity, can be determined from inelastic scattering experiments [Phys. Rev. Lett. 93, 108107 (2004), Phys. Rev. Lett. 97, 048103 (2006)]. Recently, we found first experimental evidence for a protein-protein interaction in a biological membrane under physiological conditions [accepted for publication in Phys. Rev. Lett.]. Even in simple models, biological systems must be considered as an array of units interacting through coherent reactions. Coherence must therefore be considered as a fundamental property of biomolecular systems [Phys. Rev. Lett. 101, 248106 (2008)]. So while for a long time, motions in biological materials were considered as thermally activated vibrations or librations in local potentials, at least part of the fluctuation spectrum stems from interactions. The future challenge is to understand the impact of collective molecular motions in membranes and proteins on their biological function.
Our experiments address the fundamental question how membrane composition and properties affect protein function. A possible dynamical coupling between membranes and proteins and their hydration water is important for the understanding of macromolecular function in a cellular context.
Host: Vladimir Ladizhansky