HYDRATION FORCE PARAMETERS OF PHOSPHATIDYLCHOLINE LIPID BILAYERS AS DETERMINED FROM H-2-NMR STUDIES OF DEUTERATED WATER

The continuous decrease of the quadrupolar splitting of deuterated wat er interacting with phosphocholine lipid bilayers with growing water c oncentration is analyzed as a function of the water activity. From the apparent linear dependence on water activity a measure for hydration forces is obtained. The forces calculated are in the range of publishe d data using sorption isotherms and osmotic stress technique in combin ation with SAXS. A simple interaction potential which includes orienta tional order of water adsorbed on surfaces gives a physical base for t hese findings. Therefore, deuterium NMR may become a powerful tool for hydration force analysis complementing well-known methods.