Theoretical Studies of Metal Ion Selectivity.† 2. DFT Calculations of Complexation Energies of Selected Transition Metal Ions (Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+) in Metal-Binding Sites of Metalloproteins

Abstract

To obtain a deeper understanding of metal ion selectivity exhibited by different sites in biomolecules, the interactions of selected transition metal (TM) ions with model functional groups are further studied. The hypothesis is proposed that complexation energies of TM ions in metal-binding sites of a general formula [MXn]2+ can be estimated from the interaction energies of these ions with model functional groups Xi's and the quantitative evaluation of the cooperative effect. This effect is defined as the nonadditive part of the substitution energy of two functional groups for two water molecules in an [M(H2O)n]2+ complex (reference state) in comparison with the sum of the substitution energies of the respective monosubstitutions (defining the interaction energy of Xi). The model functional groups used for the evaluation of the cooperative effect are OH -, H2S, SH -, HCHO, HCOO -, NH3, and CH3NCH2. Four coordination geometries (linear, tetrahedral, square planar, and octahedral), six transition metal ions...