Structure of water confined in the gyroid cubic phase of the lipid monoelaidin

Abstract

We present neutron diffraction studies of the structure of water confined in the gyroid bicontinuous cubic lipid-water mesophase of monoelaidin. By applying the H-D substitution method, the partial pair correlation functions g HH( r), g XH( r) could be calculated from the measured total structure factors, where H and X denote the substituted and non-substituted atoms of the samples, respectively. Experiments were performed at two pressures and levels of hydration, corresponding to two different mean water channel thicknesses. There is no evidence to suggest that the nature of the inter-bilayer water is substantially altered by interfacial interactions or to support the concept of structured water with correlations extending up to several tens of Å. Small but pronounced modifications of the HH and XH pair correlation functions are observed as compared with bulk water, however.