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α- and β-mercaptocarboxamides constitute the Zn2+-ligating entity of several highly potent metalloenzyme inhibitors. We have studied their interaction energies with Zn2+ using the polarizable molecular mechanics procedure SIBFA, and compared them to the corresponding ab initio supermolecule ones. Such validations are necessary to subsequently undertake simulations on complexes of Zn2+–metalloenzymes with inhibitors. If the distributed multipoles and polarizabilities are those derived for each ligand in its appropriate Zn2+-binding conformation, a close reproduction of the ab initio binding energies is afforded. However, this representation is not tractable upon increasing the size of the ligands and/or to explore a continuum of binding conformations. This makes it necessary to construct the ligands by resorting to a library of constitutive fragments, namely in this case methanethiolate, formamide, and methane covalently connected together. A close reproduction of the ab initio interaction energies is enabled, but only if the ligand–ligand interactions are computed simultaneously with those occurring with Zn2+. This representation accounts for the nonadditivity occurring in the Zn2+–methanethiolate–formamide complex, and justifies the use of the distributed multipoles on the fragments for the construction of larger and flexible molecules. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1038–1047, 2001 |
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