Small-Angle Neutron Scattering for Studying Lipid Bilayer Membranes

Small-angle neutron scattering (SANS) is a powerful tool for studying biological membranes and model lipid bilayer membranes. The length scales probed by SANS, being from 1 nm to over 100 nm, are well-matched to the relevant length scales of the bilayer, particularly when it is in the form of a vesicle. However, it is the ability of SANS to differentiate between isotopes of hydrogen as well as the availability of deuterium labeled lipids that truly enable SANS to reveal details of membranes that are not accessible with the use of other techniques, such as small-angle X-ray scattering. In this work, an overview of the use of SANS for studying unilamellar lipid bilayer vesicles is presented. The technique is briefly presented, and the power of selective deuteration and contrast variation methods is discussed. Approaches to modeling SANS data from unilamellar lipid bilayer vesicles are presented. Finally, recent examples are discussed. While the emphasis is on studies of unilamellar vesicles, examples of the use of SANS to study intact cells are also presented.

Effect of DMSO, urea and ethanol on hydration of stratum corneum model membrane based on short-chain length ceramide [AP]

Hydration of oriented multilamellar membrane based on ceramide [AP] in the DMSO, urea and ethanol aqueous solutions at various solute concentrations was investigated by neutron diffraction. Neither urea nor DMSO influence the repeat distance of the membrane and internal structure of bilayer at their mole concentration of up to 0.15 and 0.10, respectively. The d-spacing reduction effect of both compounds was observed at their concentrations of 0.2 for urea and 0.2 and 0.4 for DMSO. Compared to hydration in the pure water, both urea and DMSO slow down the swelling process, and this slowdown is more pronounced with increasing in their concentration. At concentration of 0.2, urea and DMSO induce the slight phase separation of the fully hydrated samples; at the highest used concentration of 0.6, DMSO induces the strong time-depend separation of the sample probably due to fluidization of lipid bilayers. Ethanol at a used molar concentration of 0.03 leads to dissolution of the sample.