Interactions at the lipid-water interface

Fourier-transform infrared (FT-IR) spectroscopy is a non-perturbing physica l technique for monitoring intra- and intermolecular interactions at the li pid-water interface. In phospholipids the sensitivity of the ester carbonyl vibrations of the fatty acyl chains to hydrogen bonding and to polarity ef fects and the use of isotopically labeled lipids has made it possible to di stinguish different hydration sites. The vibraional modes of the phosphodie ster moiety in the lipid headgroup, also sensitive to cation binding, have been studied in hydration and dehydration experiments of zwitterionic and n egatively charged lipids. In phospho- and glycosphingolipids the band posit ion of the amide I mode is an additional indicator for intra- or intermolec ular interactions with OH-groups. In this review we summarize the recent ad vances in the analysis and interpretation of FT-IR spectra of lipids and li pid mixtures with regard to hydrogen bonding and ion bonding. (C) 1998 Else vier Science Ireland Ltd. All rights reserved.