Structural studies of biological membranes and related model systems by raman spectroscopy. Sphingomyelin and 1,2-dilauroyl phosphatidylethanolamine

Raman spectra are reported at relatively high resolution (1.5 cm^-1) for sphingomyelin and for 1,2-dilauroyl phosphatidylethanolamine above and below their melting temperatures. The spectra of 1,2-dilauroyl phosphatidylethanolamine below T_m show the hydrocarbon chains to be less ordered in the solid phase than the fatty acid of the same chain length, without the significant occurrence of gauche isomers. The spectra of sphingomyelin show significant formation of gauche isomers below T_m, indicating a less rigid environment for this molecule in the solid state.