Interaction of L-cysteine with selenious and selenic acids: A study by the density functional theory method

Abstract

Using the density functional theory method at the B3LYP/6-31G(d,p) theory level, the formation of hydrogen bonded complexes of L-cysteine with selenious and selenic acids is studied. In both cases, complexes formed through the carboxyl group of cysteine mostly arise, their enthalpy of formation being of -19kcal/mol to -21 kcal/mol and the free energy of -6kcal/mol to -9kcal/mol. The primary act of interaction in the system of hydroxyl-containing selenium compound — α-aminoacid, including the mutual orientation of reactant molecules and the formation of intermolecular hydrogen bonds is likely to a serve as prerequisite for the thiol group to be able to participate in the next stages (including deeper chemical transformations) of biologically significant reactions.