Aromatic Residues Regulating Electron Relay Ability of S-Containing Amino Acids by Formations of S∴π Multicenter Three-Electron Bonds in Proteins

Abstract

The ab initio calculations predict that the side chains of four aromatic amino acids (Phe, His, Tyr, and Trp residues) may promote methionine and cystine residues to participate in the protein electron hole transport by the formation of special multicenter, three-electron bonds (S∴π) between the S-atoms and the aromatic rings. The formations of S∴π bonds can efficiently lower the local ionization energies, which drive the electron hole moving to the close side chains of S-containing and aromatic residues in proteins. Additionally, the proper binding energies for the S∴π bonds imply that the self-movement of proteins can dissociate these three-electron bonds and promote electron hole relay.