SPECTROSCOPIC STUDIES OF MODEL BIOLOGICAL-MEMBRANES IN VESICLES AND LANGMUIR-BLODGETT-FILMS

Fourier transform infrared spectroscopic analyses of egg phosphatidylc holine have been undertaken for the solution state for unilamellar ves icles, for films cast from chloroform, and for Langmuir-Blodgett films . These showed that the phospholipid chains of the vesicles have a hig h proportion of gauche conformations but that both the chains and the head groups show evidence of alignment in an ''ordered'' environment. Both the head group and a proportion of the ester carbonyl groups are hydrated and published evidence of a trans/gauche population distribut ion (at the COC group) has been confirmed. Previous contradictory inte rpretations of the COC conformation have been reconciled. There is cle ar evidence of water associated with the lipid when it is cast either from chloroform or from a vesicle solution. The incorporation of alame thicin into (Z-type) LB bilayers has been successfully achieved, and e vidence of strong lipid head group/peptide interactions has been found . The peptide conformation appears to be unchanged while the lipid cha ins retain their essentially all-trans configuration. There is some ev idence that the incorporation level is lower than the initial mixture content, at least under some dipping conditions, and that peptide aggr egation is not extensive.