5 years ago

Hydrogen-Bond Strength of CC and GG Pairs Determined by Steric Repulsion: Electrostatics and Charge Transfer Overruled

Hydrogen-Bond Strength of CC and GG Pairs Determined by Steric Repulsion: Electrostatics and Charge Transfer Overruled
Célia Fonseca Guerra, Stephanie C. C. van der Lubbe
Theoretical and experimental studies have elucidated the bonding mechanism in hydrogen bonds as an electrostatic interaction, which also exhibits considerable stabilization by charge transfer, polarization, and dispersion interactions. Therefore, these components have been used to rationalize the differences in strength of hydrogen-bonded systems. A completely new viewpoint is presented, in which the Pauli (steric) repulsion controls the mechanism of hydrogen bonding. Quantum chemical computations on the mismatched DNA base pairs CC and GG (C=cytosine, G=guanine) show that the enhanced stabilization and shorter distance of GG is determined entirely by the difference in the Pauli repulsion, which is significantly less repulsive for GG than for CC. This is the first time that evidence is presented for the Pauli repulsion as decisive factor in relative hydrogen-bond strengths and lengths. When electrons come too close: The Pauli repulsion can be a decisive factor for relative hydrogen bonding strengths and lengths. This study on DNA base pairs highlights the complex nature of hydrogen bonds, which are an interplay between steric, electrostatic, covalent, cooperative, and π-resonance interactions, and emphasizes the importance of state-of-the-art quantum chemical analysis to shed light on their bonding mechanism.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701821

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