Comparison of DFT, Moller-Plesset, and coupled cluster calculations of theproton dissociation energies of imidazole and N-methylacetamide in the presence of zinc(II)

We report herein a comparison of DFT, Moller-Plesset, and coupled cluster c alculations of the proton dissociation energies of imidazole and N-methylac etamide in the presence of the zinc divalent cation. Despite the MP2 calcul ation showing that the proton dissociation energy of the zinc-bound imidazo le was 4 kcal/mol higher than that of the zinc-bound N-methylacetamide, all the higher-level Moller-Plesset, DFT, and coupled-cluster calculations rev ealed that the proton dissociation energy of the zinc-bound imidazole was 4 -10 kcal/mol lower than that of the zinc-bound N-methylacetamide. The resul ts support the reported hypothesis of imidazolate as a zinc ligand in prote ins. (C) 2001 Elsevier Science B.V. All rights reserved.