Table of Contents
ISRN Biophysics
Volume 2013, Article ID 439758, 9 pages
http://dx.doi.org/10.1155/2013/439758
Research Article

Incoherent Neutron Spin-Echo Spectroscopy as an Option to Study Long-Range Lipid Diffusion

1Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada L8S 4M1
2NIST Center for Neutron Research, NIST, Gaithersburg, MD 20899-6100, USA
3Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
4Center for Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408-1398, USA
5Canadian Neutron Beam Centre, National Research Council of Canada, Chalk River, ON, Canada K0J 1J0

Received 4 February 2013; Accepted 25 February 2013

Academic Editors: E. Dague and K. Nishizawa

Copyright © 2013 Clare L. Armstrong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Diffusion is the fundamental mechanism for lipids and other molecules to move in a membrane. It is an important process to consider in modelling the formation of membrane structures, such as rafts. Lipid diffusion is mainly studied by two different techniques: incoherent neutron scattering and fluorescence microscopy. Both techniques access distinctly different length scales. While neutron scattering measures diffusion over about 3 lipid diameters, microscopic techniques access motions of lipids over micrometer distances. The diffusion constants which are determined by these two methods often differ by about an order of magnitude, with the neutrons usually seeing a faster lipid diffusion. Different theories are used to describe lipid diffusion in the two experiments. In order to close the “gap” between these two techniques, we propose to study lipid diffusion at mesoscopic length scales using a neutron spin-echo (NSE) spectrometer. We have conducted an experiment in highly oriented, solid supported lipid bilayers to prove the feasibility of performing incoherent NSE on biological samples. Lateral lipid diffusion was measured in a fluid phase model membrane system at a length scale of 12 Å. Using the high-energy resolution of the NSE technique, we find evidence for two dynamic processes.