Ab initio calculation of the anisotropic/ring current effects of amino acid residues to locate the position of substrates in the binding site of enzymes

The ring current effects of aromatic moieties and the anisotropic effects of the CyO and C–X (X ¼ C, N, S) bonds and of the NHyC(NH2)–NH– moiety in the side chains of amino acid residues of proteins were ab initio calculated based on nuclear independent chemical shieldings as employed by P.v.R. Schleyer. Hereby, quantitative information about the spatial extension, sign and scope of the corresponding ring current/anisotropic effects was obtained and they were visualized as iso-chemical-shielding-surfaces. Examining this quantitative information compared with experimental NMR chemical shifts, the role of the corresponding amino acid residues in binding substrates in the binding site of enzymes was studied. q 2004 Elsevier B.V. All rights reserved.