Determination of the conformational order of lipid membranes from Raman spectroscopy

Raman spectroscopy demonstrated that (1) in pure lipid membranes (dihexadecylphosphatidic acid or phosphatidylcholines), the lipid chains are mainly in an all-trans conformation in the ordered membrane phase, and in the fluid phase, lipid chains contain all-trans segments of 11 or 8 C atoms, resp.; (2) in charged membranes (dimyristoylmethylphosphatidic acid at pH 9), in addn. to a phase transition shift from 46 to 32 Deg, the lipid chain conformation is disordered, and the disordering effect is concd. at the chain ends; and (3) the presence of proteins (melittin) in dimyrisytoylphosphatidylcholine membranes decreases the conformational order below the phase transition temp., with a slight increase in the conformational order being obsd. in the fluid phase. [on SciFinder (R)]