Two-dimensional classification of amphiphilic monomers based on interfacial and partitioning properties. 2. Amino acids and amino acid residues

A new classification for amino acid residues is proposed, based on interfacial and partitioning properties. Amino acid residues are characterized by two parameters: standard free energy of adsorption at the hexane/water interface and standard free energy of the partition between hexane and water. Theoretical approaches are used for the estimation of these parameters. As a result, several groups of amino acid units having close values of the parameters are distinguished. Classification of the amino acid units by such a method is believed to be able to provide promising results in the search of correlations in protein sequences. The comparison of experimental and theoretical studies of free amino acids at the hexane/water interface confirm the predictive power of the theory used, because a very good coincidence between theoretical and experimental data points is observed. The obtained values of standard free energies of adsorption are consistent with literature data.