The behavior of water molecules in the most stable subgel phase of dimyristoylphosphatidylethanolamine-water system as studied by differential scanning calorimetry

摘要

The number of water molecules in different bonding modes were estimated from ice-melting DSC curves for the most stable subgel phase of dimyristoylphosphatidylethanolamine (DMPE)-water system at different water contents, and used to prepare a water-distribution diagram up to a full hydration. By the present study, it was revealed that approximately 5 H2O of water molecules per lipid present as members of the interlamellar water in the gel phase are excluded outside the bilayers during periods of thermal annealing for the conversion to the most stable subgel phase. The dehydrated subgel phase was found to involve 1 H2O of the freezable interlamellar water per lipid, via which adjacent bilayers are linked. Furthermore, almost no interlamellar water was found in intrabilayer regions between the head groups of the present subgel phase, in contrast with approximately 2 H2O of water molecules per lipid for the intrabilayer regions of the gel phase. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 18]