Effect of amino acid sequence on the hydrophobicity of small peptides

Hydrophobic adsorbents, which contain alkyl ligands of various chain lengths, were used to study the hydrophobic interactions between alkyl chains and small peptides. We investigated the adsorption of four similar peptides: GWWG, GWGW, WGWG, WGGW. All of them contained two glycines (G) and two tryptophans (W) but the amino acids were arranged in different orders. The capacity factors of peptides between 10 and 35 °C were measured and then the thermodynamic parameters, such as enthalpy and entropy changes (ΔH° and ΔS°) of adsorption, were estimated. lied that enthalpy was the major driving force in all the adsorption processes. Furthermore, ΔH° and ΔS° became more negative as the alkyl chain length was increased. It revealed that the van der Waalʹs interaction had greater influence on the adsorption as the chain length increased. It was also found that, the contribution of each amino acid to peptideʹs hydrophobicity was affected by the position of the amino acid. When a hydrophobic amino acid was positioned in the middle of a peptide chain, it exhibited the highest hydrophobicity. Interestingly, tryptophan at the carboxyl end was found more hydrophobic than it at the amino end of the peptide.