Quantum-chemical study of C–H···O interactions between HTcO4 and aromatic amino acids Scientific paper

Abstract

This study investigates C–H···O interactions between HTcO₄ and aromatic amino acids (phenylalanine, tyrosine and tryptophan) through quan­tum-chemical calculations. The interaction energies calculations were com­bined with the analysis of molecular electrostatic potentials (MEP) to under­stand the nature of these interactions. The strongest interaction was observed for the HTcO₄–tryptophan with an energy minimum of –9.53 kJ/mol at a dis­tance of 2.1 Å. Phenylalanine showed a similarly strong interaction, with a minimum of –9.49 kJ/mol, while tyrosine exhibited the weakest interaction, with a minimum of –8.61 kJ/mol. Electrostatic potential maps confirmed the electrostatic nature of the C–H···O interactions, highlighting the role of the oxygen atoms in acting as hydrogen bond acceptors. These findings suggest that the position of the hydrogen atoms relative to the substituents on the arom­atic ring influences the strength of the interactions. The results presented here could be of great importance for the recognition of new, overlooked noncov­alent contacts between pertechnetic acid and amino acid fragments and a better understanding of the stability of pertechnetate-peptide complexes.