Table of Contents
ISRN Biophysics
Volume 2012 (2012), Article ID 520307, 7 pages
http://dx.doi.org/10.5402/2012/520307
Research Article

Hydration Water Freezing in Single Supported Lipid Bilayers

1Department of Physics & Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4M1
2NIST Center for Neutron Research, NIST, Gaithersburg, MD 20899, USA
3Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
4Canadian Neutron Beam Centre, National Research Council Canada, Chalk River, ON, Canada K0J 1J0

Received 2 January 2012; Accepted 31 January 2012

Academic Editors: J. P. Bradshaw, L. Loura, and J. Perez-Gil

Copyright © 2012 Laura Toppozini 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

We present a high-temperature and high-energy resolution neutron scattering investigation of hydration water freezing in single supported lipid bilayers. Single supported lipid bilayers provide a well-defined biological interface to study hydration water dynamics and coupling to membrane degrees of freedom. Nanosecond molecular motions of membrane and hydration water were studied in the temperature range 240 K < T < 290 K in slow heating and cooling cycles using coherent and incoherent elastic neutron scattering on a backscattering spectrometer. Several freezing and melting transitions were observed. From the length scale dependence of the elastic scattering, these transitions could be assigned to freezing and melting of hydration water dynamics, diffusive lipid, and lipid acyl-tail dynamics. Coupling was investigated by comparing the different freezing and melting temperatures. While it is often speculated that membrane and hydration water dynamics are strongly coupled, we find that membrane and hydration water dynamics are at least partially decoupled in single bilayers.