Hydration of phosphatidylocholine. Adsorption isotherm and proton nuclear magnetic resonance studies

Adsorption-desorption isotherms were obtained for water binding by 1,2-dimyristoylphosphatidylcholine in the temperature range 15 degrees-35 degrees C. The isotherms were analyzed by Brunauer et al.'s (BET) theory and also a polarization theory, the latter being more successful in fitting the data. There was some evidence for a change in the surface field of the lipid bilayer around 25 degrees C. Proton T1 and T2 measurements were used to obtain a log-normal molecular correlation time distribution for water protons in these systems. This distribution was compared with the isotherm data to effect a description of several classes of water molecules.