Infrared attenuated total reflection spectroscopic studies on the hydration of the gramicidin a transmembrane channel

Abstract

The hydration of gramicidin incorporated in lipid bilayers has been studied by FT-IR-ATR spectroscopy. The dependence of the stability of the system on the water environment of the polypeptide moiety and of the structural water of the lipid bilayer is discussed. The results indicate that partial drying of the gramicidin-lipid system first removes the water molecules bound to the peptide groups of the polypeptide moiety stabilizing its helical structure. Removal of water molecules bound tightly to the phosphate and choline head groups of the lipid produces a destabilization of the lipid bilayer, perturbing all the system. Our observations are compatible with a conformational transformation of gramicidin upon drying.