Deuteron spectroscopy and deuteron field-cycling nuclear magnetic resonance relaxometry of the hydration water of lipid bilayers: The corrugated-sheet model for interface molecular dynamics in the ripple phase

Abstract

Lipid bilayers are known to form the so-called ripple phase in a certain temperature interval between the gel and the liquid crystalline phase transitions. The dynamics of heavy water at the corrugated water/lipid interface was studied with the aid of field-cycling nuclear magnetic resonance (NMR) relaxometry and NMR spectroscopy of the water deuterons. Based on the “reorientation mediated by translational displacement” relaxation mechanism, model calculations were carried out. It is shown that the features of the spin-lattice relaxation dispersion and the coalescence of the deuteron quadrupole splitting in the ripple phase commonly are a consequence of the geometrical surface topology. The deuteron splitting and T1 dispersion data for the ripple phase can be explained in complete accordance with the results of freeze etching electron microscopy and tunneling microscopy. That is, the structural surface features are mirrored in the reorientational dynamics of hydration water.