Microsolvation of Mg2+, Ca2+: Strong influence of formal charges in hydrogen bond networks

Juan David Gonzalez, Elizabeth Florez, Jonathan Romero, Andrés Reyes, Albeiro Restrepo

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29 Scopus citations

Abstract

A stochastic exploration of the quantum conformational spaces in the microsolvation of divalent cations with explicit consideration of up to six solvent molecules [Mg (H2 O)n )]2+, (n = 3, 4, 5, 6) at the B3LYP, MP2, CCSD(T) levels is presented. We find several cases in which the formal charge in Mg2+ causes dissociation of water molecules in the first solvation shell, leaving a hydroxide ion available to interact with the central cation, the released proton being transferred to outer solvation shells in a Grotthus type mechanism; this particular finding sheds light on the capacity of Mg2+ to promote formation of hydroxide anions, a process necessary to regulate proton transfer in enzymes with exonuclease activity. Two distinct types of hydrogen bonds, scattered over a wide range of distances (1.35-2.15 Å) were identified. We find that in inner solvation shells, where hydrogen bond networks are severely disturbed, most of the interaction energies come from electrostatic and polarization+charge transfer, while in outer solvation shells the situation approximates that of pure water clusters. © 2013 Springer-Verlag Berlin Heidelberg.
Original languageAmerican English
Pages (from-to)1763-1777
Number of pages15
JournalJournal of Molecular Modeling
Volume19
Issue number4
DOIs
StatePublished - 1 Apr 2013

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