%0 Journal Article %T Hydration Water Freezing in Single Supported Lipid Bilayers %A Laura Toppozini %A Clare L. Armstrong %A Martin D. Kaye %A Madhusudan Tyagi %A Timothy Jenkins %A Maikel C. Rheinst£¿dter %J ISRN Biophysics %D 2012 %R 10.5402/2012/520307 %X 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. 1. Introduction Despite the vast potential for applications of single membranes in biotechnology and fundamental research [1, 2], experiments using single membranes are challenging, mainly because of the small amounts of sample material and corresponding small sample signals. Recent developments in neutron scattering instrumentation, and the increasingly powerful neutron sources, have made it possible to experimentally address molecular dynamics in single bilayers. Lipid diffusion in single supported bilayers made of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine) was studied recently using quasielastic neutron scattering [3]. A freezing transition at T = 271£¿K was reported and associated with freezing of hydration water molecules. Here, we used solid-supported single-lipid bilayers as a well-defined biological interface to study freezing and melting of hydration water and membrane. We report a high-energy and temperature-resolution neutron scattering study using a backscattering spectrometer in a temperature range between 240£¿K and 290£¿K. While the temperature range 100£¿K < T < 220£¿K was investigated thoroughly in the literature to study the so-called ¡°dynamical transition¡± in hydrated protein and membrane systems, much less attention was paid to the onset of freezing at 271£¿K in the past. By analyzing the length scale dependence of the elastic coherent and incoherent scattering, freezing of hydration water and membrane dynamics was observed, and the corresponding freezing %U http://www.hindawi.com/journals/isrn.biophysics/2012/520307/