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

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.