Abstract
Some recent topics concerning to the structure and properties of lipid bilayers are reviewed with the special reference to hydrophobic hydration. The partial molar heat capacity per CH2 group in the aqueous dispersions of phospholipids is much larger than the heat capacity per CH2 group in solid paraffins. The reason for the large heat capacity is well interpreted by hydrophobic hydration of CH2 groups within the phospholipid bilayers. The mixing enthalpies of the aqueous dispersions of triphosphoinositide (TPI) and the aqueous CaCl2 solution are positive, while those of glycerylphosphoryl-inositoldiphosphate (GPIDP, the hydrophilic part in TPI) are negative at lower concejtrations of CaCl2. The positive contribution of the hydrocarbon chains in TPI to the mixing enthalpy is attributed to the dehydration of lipid bilayers induced by Ca2+ ions. The water adsorption experiment shows that the amount of hydrophobic hydration of the unsaturated acyl chains in the lipid bilayers is much higher than that of the saturated chains.
