THE SOLUBILITY OF HYDROCARBON GASES IN PROTEIN SOLUTIONS

Abstract

A study of the solubility of butane, propane, and ethane in solutions of BSA, Hb, lysozyme, and SLS has established three points. (1) The usually large (lysozyme is an exception) solubility increment represents a direct interaction between the gas and the other solute, best understood as solubility in a nonpolar material. (2) The [DELTA] H of transfer of gas from water to the macro solute is close to zero, confirming the prediction by Kauzmann and others that the contribution of hydrophobic interactions toward stabilizing folded protein structures arises primarily from entropy changes. (3) Results obtained on BSA with propane, butane, and by other workers, isooctane suggest that the investigation of the relative and absolute solubilities of a graded series of alkanes may provide an estimate of the number and size of hydrophobic clusters in a given protein.