Theoretical sight into hydrogen bond interactions between arsenious acid and thiols in aqueous and HEPES solutions

Abstract

Thiols compounds can be used as monomers of arsenious acid (H3AsO3) molecular-imprinted polymers to specifically recognize arsenic owing to the high affinity between arsenic and thiol. However, the recognition and binding interaction mechanisms between arsenious acid and thiol monomers remain unclear. Herein, the mechanisms of binding interaction between H3AsO3 and DTT/DTE in aqueous solution and HEPES solution were studied by quantum-chemistry calculations of density functional theory with dispersion correction (DFT-D). The most stable configurations of H3AsO3-DTT/DTE complex, connecting with O···H-O and S···H-O hydrogen bonds in the form of double-teeth were found out. In aqueous solution and HEPES solution, with polarizable continuum model, the calculated binding energies show that H3AsO3 has larger affinity towards DTT than DTE. However, in the explicit solvent model where HEPES molecule indeed participates in the hydrogen-bond binding, H3AsO3 combining with DTE (HEPES-H3AsO3-DTE) is more favorable than with DTT (HEPES-H3AsO3-DTT), which agrees well with experimental results. This finding suggests the effect of buffer solution cannot be ignored when selecting monomers for molecular-imprinted polymers. Reduced density gradient method reveals that the binding interactions are composed of hydrogen bonds, Van Der Waals force and repulsion force, while hydrogen bonds play a dominant role. Furthermore, the essence of those hydrogen bonds is identified to be electrostatic force in nature.