| The nature of the interactions between dihydrosphingomyelin (DHSM) and cholesterol (CHoI), the most abundant lipids in human lens membranes was investigated using FTIR spectroscopy. To establish the role of the 3β-OH group of CHoI, mixtures of DHSM and CHoI or analogs with and without this group were analyzed. Significant hydrocarbon-chain order was induced by addition of CHoI or dihydrocholesterol. Simultaneously, the Amide I′ band of DHSM exhibited a red shift indicative of strong H-bond formation. Such shifts were not observed with cholestane or cholestane. These results indicate the participation of the 3β-OH group in H-bonding interactions.; As the relative amount of CHoI was changed, CHoI bound to DHSM less effectively for molar ratios of CHoI to DHSM of 0.75 or greater. This suggests the formation of CHoI clusters surrounding pools of DHSM and CHoI. Spectral shifts indicate stronger interactions between CHoI and DHSM than with sphingomyelin. |
