Interactions at the lipid-water interface

Fourier-transform infrared (FT-IR) spectroscopy is a non-perturbing physical technique for monitoring intra- and intermolecular interactions at the lipid-water interface. In phospholipids the sensitivity of the ester carbonyl vibrations of the fatty acyl chains to hydrogen bonding and to polarity effects and the use of isotopically labeled lipids has made it possible to distinguish different hydration sites. The vibraional modes of the phosphodiester moiety in the lipid headgroup, also sensitive to cation binding, have been studied in hydration and dehydration experiments of zwitterionic and negatively charged lipids. In phospho- and glycosphingolipids the band position of the amide I mode is an additional indicator for intra- or intermolecular interactions with OH-groups. In this review we summarize the recent advances in the analysis and interpretation of FT-IR spectra of lipids and lipid mixtures with regard to hydrogen bonding and ion bonding. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.