The relationship between hydrophobicity and interfacial tension of proteins

Charge-free hydrophobic gels of Hjerten et al. (Hjerten, S., Rosengren, J. and Pahlman, S. (1974) J. Chromatogr. 101, 281--288) were used for hydrophobic affinity chromatography. The effective hydrophobicity of proteins was expressed as their retention volumes from columns of butylepoxy- and hexylepoxy-Sepharose 4B. The effective hydrophobicity was also estimated by a partition method of Shanbhag and Axelsson ((1975) Eur. J. Biochem. 60, 17--22) from the partition coefficients of proteins between two phases, poly (ethylene glycol) and dextran. The former contained a hydrophobic ligand, palmitate. A close correlation was observed between the hydrophobicities determined by the two methods. However, no significant relationship was observed between these effective hydrophobicities and the average hydrophobicity of Bigelow ((1967) J. Theoret. Biol. 16, 187--211) that was calculated from the total amino acid composition of each protein. The interfacial tensions at the 0.2% protein/corn oil interface revealed negative correlations with the effective hydrophobicities determined by both methods indicating lower interfacial tensions with more hydrophobic proteins.