Ab initio calculations of the pyrophosphate hydrolysis reaction

Humberto Saint-Martin, Iván Ortega Blake, Andrzej Leś, Ludwik Adamowicz

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Ab initio quantum mechanical calculations were used to study the hydrolysis H4P2O7 + H2O2H3PO4, as well as some molecular properties of the reactants and products. SCF calculations with several basis sets ranging from minimal to extended with polarization functions were used to look at the basis dependency of the reaction enthalpies and optimized geometries. Although the minimal basis sets yield erratic predictions of the enthalpy, when a more extended basis (3-21G*) was used for the geometry optimization, and the total energies of the reactants and products were computed with this and larger basis sets, we obtained more consistent predictions of the structural properties of the POP bridge and of the heat of the hydrolysis reaction (ΔE = -7.39 kcal/mol at the SCF/6-31G** level). A comparison is made with previous estimates performed with smaller basis sets and without taking into account the electron correlation effects, which are calculated in the present work. The inclusion of the zero point energy calculated using the harmonic approximation, and of the electronic correlation energy determined at the MBPT(2) level, raised the computed heat of the reaction to -3.83 kcal/mol, and when an estimate for the thermal energy was added, the value obtained was of -3.38 kcal/mol. In conclusion, we found that the hydrolysis of pyrophosphate should be exothermic in the gas phase. The implications of this result in relation to some recent theories about enzyme catalysis are discussed.

Original languageEnglish (US)
Pages (from-to)205-214
Number of pages10
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume1080
Issue number3
DOIs
StatePublished - Nov 15 1991

Keywords

  • Ab initio calculation
  • Enzyme mechanism
  • Gas-phase reaction
  • Pyrophosphate hydrolysis

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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