Thermodynamics of transfer of noble gases in hydrophobic solvents and in phospholipid membranes

Abstract

A theory of gas solubility has been formulated and tested using solubility data of noble gases in several hydrophobic solvents and in a phospholipid membrane of dimyristoyl lecithin. The theory describes solubility in terms of two independent processes: hole creation in the solvent and solute adsorption in these holes. It gives the standard thermodynamic functions of solution in terms of four independent microscopic parameters. Two parameters reflect the nature of the pure solvent and the others the nature of the solute and its interactions with the solvent. Examination reveals good agreement between theory and experiment for the solvents tested, paving the way for comparisons between membranes and bulk solvents which are more significant than the existing correlations. The characteristics of the theory and its agreement with experiment suggest an interesting method for evaluating, from the solubility data of gases, the physical properties of hydrophobic regions of membranes and of other solvents which cannot be measured directly.