The understanding of biological processes at the molecular level demands accurate knowledge of the nonbonded interactions that control the geometries, binding energies and dynamics of the supramolecular structures involved. High level ab initio methods are still prohibitively
expensive for large systems, but certain density functional (DFT) methods can provide cost-effective alternatives. The performance of six different functionals (BLYP, B3LYP, X3LYP, PBE, PW91, and mPW91) for the calculation of the doubly hydrogen-bonded cis-amide dimers (formamide)2
and (2-pyridone)2 have been tested. Their N-H···O hydrogen bond motifs occur between many nucleobases, peptides, and proteins. Binding energy benchmarks using ab initio MP2 calculations and basis set extrapolations to the complete basis set (CBS) limit
with the Dunning aug-cc-pVXZ (X=D,T,Q) basis set series have been established. These yield D
= −14.80 kcal/mol for (formamide)2 and −22.63 kcal/mol for (2PY)2. Of the six functionals, PW91 consistently gives the
best agreement with the MP2 basis-set limit binding energies, closely followed by PBE. The mPW91, B3LYP and the recently proposed X3LYP functionals are in less good agreement. The BLYP functional underestimates the interaction strengths by 20–25% and is not recommended. As an application
the hydrogen-bond isomerization equilibria for the Sugar-edge, Watson-Crick and Wobble isomers of the dimers 2-pyridone·uracil and 2-pyridone·thymine from first principles are computed and compared to experiment.
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Document Type: Research Article
July 1, 2005
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International Journal for Chemistry and Official Membership Journal of the Swiss Chemical Society (SCS) and its Divisions
CHIMIA, a scientific journal for chemistry in the broadest sense, is published 10 times a year and covers the interests of a wide and diverse readership. Contributions from all fields of chemistry and related areas are considered for publication in the form of Review Articles and Notes. A characteristic feature of CHIMIA are the thematic issues, each devoted to an area of great current significance.
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