Lipid-protein interactions in human and bovine lens membranes by Fourier transform Raman and infrared spectroscopies.

In other systems, proteins have been shown to alter the molecular structures of lipids in the cell membrane bilayer. We wished to determine if proteins altered the structure of lens lipids. The structure of lipid hydrocarbon chains in urea purified human lens membrane vesicles containing intrinsic, hydrophobically bound proteins was compared to the structure of lipids in vesicles without protein. Fourier transform Raman spectroscopy was used to characterize lipid and protein structure. To study lipid interactions with extrinsic, surface bound proteins, the lipid structure was compared in bovine lipid vesicles with and without alpha-crystallin bound to the surface of the membrane. Lipid structure was studied using Fourier transform infrared spectroscopy. No change in lipid structure was detected even at protein/lipid weight ratios of two to one. Human lens intrinsic proteins contained a high amount of a helical structure (60%), but did not alter hydrocarbon chain interactions.