Configuration of Carbonyl Groups at the Lipid Interphases of Different Topological Arrangements of Lipid Dispersions

MARÍA DE LOS ANGELES FRIAS; E. ANIBAL DISALVO

LANGMUIR

AMER CHEMICAL SOC

Año: 2009 vol. 25 p. 8187 - 8191

0743-7463

The purpose of this work is to analyze the conformation of the carbonyl groups of acyl phospholipids at the hydrocarbon−water interphase in different topological ensembles and phase states, such as micelles and bilayers. The separation of the band components in lipids dispersed in D2O is compared with that of PCs in a low hydrated state. When hydrated, the differences in the frequencies of the band components corresponding to the carbonyl groups identified as low hydrated and hydrated populations increase when dimyristoylphosphatidylcholine (DMPC) bilayers go from the lamellar gel to the ripple corrugated phase at the pretransition temperature. Below the pretransition, at which the membrane in the gel state is planar, the two components overlap making the deconvolution unreliable. A further analysis shows that the frequency of the highly hydrated population increases more noticeable than that corresponding to the low hydrated one following the sequence: micelles, fluid phase, ripple gel phase, and lamellar gel phase. This is confirmed by the increase in the separation of the band components when the liposomes are subjected to an osmotic dehydration suggesting that the hydrated population loses water and the dehydrated one partially hydrates. It is concluded that this behavior is a feature conferred by hydration of the different topological arrangements. The relevance of these results on the interphase properties of lipid membranes is discussed.