Effects of cholesterol on membrane molecular dynamics studied by fast field cycling NMR relaxometry.

Biological membranes are complex structures composed of various lipids and proteins. Different membrane compositions affect viscoelastic and hydrodynamic properties of membranes, which are critical to their functions. Lipid bilayer vesicles inserted by cholesterol not only enhance membrane surface motional behavior but also strengthen vesicle stability. Cholesterol-rich vesicles are similar to cell membranes in structure and composition. Therefore, cholesterol-rich vesicles can represent a typical model for studying membrane dynamics and functions. In this study, nuclear magnetic relaxation dispersion was used to investigate the detailed molecular dynamics of membrane differences between vesicles and cholesterol vesicles in the temperature range of 278-298 K. Vesicles of two different sizes were prepared. The effect of cholesterol mainly affected the order fluctuation of membranes and the diffusional motion of lipid molecules. In addition, phase variations were also observed in liposomes that contained cholesterol from analyses of the distances between lipid molecules.