Hydration in purple membrane as a function of relative humidity

Abstract

Neutron diffraction experiments on the purple membrane of Halobacterium halobium as a function of H 2OD 2O exchange in a wide relative humidity range, are described. Increasing relative humidity leads primarily to hydration of the lipid area in the membrane. The exchanged H density is higher in the centre of the protein than at the protein-lipid interface, in support of the hypothesis that the molecule has a hydrophilic interior. However, there is no aqueous pocket in the protein.