Amino acid-amino acid interactions studied by charge-transfer chromatography

The interaction between amino acids was studied by charge-transfer reversed-phase thin-layer chromatography. The dependence of the lipophilicity of Trp on the concentration of other amino acids in the eluent was considered to be linearly related to the strength of interaction. Arg, Asn, Glu, Met, Phe and Thr interacted with Trp; Ala, Gly and Ser showed no interaction. Stepwise regression analysis indicated that the pK value of the amino acid side-chain and the lipophilicity of the amino acid had the greatest impact on the interaction, suggesting the simultaneous presence of weak hydrophilic and hydrophobic bonding forces between amino acids. Sodium acetate in the eluent increased the interactive strength between Phe and Trp; acetic acid and sodium chloride did not influence the interaction significantly. No significant difference was found between the effects of l- and d-Asn.