Affinity Scale for the Interaction of Amino Acids with Silica Surfaces

A systematic computational study of the adsorption of 15 different amino acids (AA) (Gly, Ala, Met, Phe, Ser, Thr, Cys, Tyr, Asn, Gln, Asp, Glu, His, Lys, and Arg) on a hydroxylated silica surface has been addressed by ab initio ONIOM2(B3LYP/6-311++G(d,p):MNDO) method within a cluster approach. A model cluster cut out from the (001) surface of an all-silica edingtonite terminated by silanol groups (2.2 OH nm−2) was used to simulate the surface. The adsorption process is mainly dictated by the hydrogen-bond (H-bond) interactions between both the COOH moiety and the side-chain functionalities of the considered AA and the terminal silanol groups of the surfaces. The computed adsorption energies were corrected for basis set superposition error and the role of dispersive interactions, not accounted for by the B3LYP functional, were estimated in a posterior fashion showing to be substantial for the adsorption free energies. Large AA and rich in hydrophilic functionalities in the lateral chain exhibit the most f...