Limits...
The Role of Aromaticity, Hybridization, Electrostatics, and Covalency in Resonance-Assisted Hydrogen Bonds of Adenine-Thymine (AT) Base Pairs and Their Mimics.

Guillaumes L, Simon S, Fonseca Guerra C - ChemistryOpen (2015)

Bottom Line: In this study, we show quantum chemically that neither aromaticity nor other forms of π assistance are responsible for the enhanced stability of the hydrogen bonds in adenine-thymine (AT) DNA base pairs.Removing the aromatic rings of either A or T has no effect on the Watson-Crick bond strength.Bonding analyses based on quantitative Kohn-Sham molecular orbital theory and corresponding energy decomposition analyses (EDA) show that the stronger hydrogen bonds in the unsaturated model complexes and in AT stem from stronger electrostatic interactions as well as enhanced donor-acceptor interactions in the σ-electron system, with the covalency being responsible for shortening the hydrogen bonds in these dimers.

View Article: PubMed Central - PubMed

Affiliation: Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona 17071, Girona, Spain).

ABSTRACT
Hydrogen bonds play a crucial role in many biochemical processes and in supramolecular chemistry. In this study, we show quantum chemically that neither aromaticity nor other forms of π assistance are responsible for the enhanced stability of the hydrogen bonds in adenine-thymine (AT) DNA base pairs. This follows from extensive bonding analyses of AT and smaller analogs thereof, based on dispersion-corrected density functional theory (DFT). Removing the aromatic rings of either A or T has no effect on the Watson-Crick bond strength. Only when the smaller mimics become saturated, that is, when the hydrogen-bond acceptor and donor groups go from sp (2) to sp (3), does the stability of the resulting model complexes suddenly drop. Bonding analyses based on quantitative Kohn-Sham molecular orbital theory and corresponding energy decomposition analyses (EDA) show that the stronger hydrogen bonds in the unsaturated model complexes and in AT stem from stronger electrostatic interactions as well as enhanced donor-acceptor interactions in the σ-electron system, with the covalency being responsible for shortening the hydrogen bonds in these dimers.

No MeSH data available.


Energy decomposition analysis for A“T” and a“t” at the equilibrium distance R(sp2) of A“T” and at the equilibrium distance R(sp3) of a“t”.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4522182&req=5

fig09: Energy decomposition analysis for A“T” and a“t” at the equilibrium distance R(sp2) of A“T” and at the equilibrium distance R(sp3) of a“t”.

Mentions: The decomposition of the interaction energy is presented in graphical form in Figure 9 at the R(sp2) and R(sp3) distances. The augmentation of Pauli repulsion by compressing the dimers A“T” and a“t” from R(sp3) to the R(sp2) distance has to be overcome by the attractive contributions to the bonding energy. The electrostatic interaction gains for both dimers equally, and the dispersion correction does not change much by the compression. The largest difference due to the shortening is seen in the orbital interaction: A“T” gains more rapidly (blue line in ΔEoi) than a“t” (red line in ΔEoi). Decomposition of ΔEoi of A“T” into ΔEσ and ΔEπ of A“T” shows that it is the σ component in the orbital interaction (green line) that is responsible for strengthening the hydrogen bonds for the sp2-hybridized dimers, as it increases more rapidly. This results in an equilibrium structure of A“T” with shorter hydrogen bonds than for a“t”.


The Role of Aromaticity, Hybridization, Electrostatics, and Covalency in Resonance-Assisted Hydrogen Bonds of Adenine-Thymine (AT) Base Pairs and Their Mimics.

Guillaumes L, Simon S, Fonseca Guerra C - ChemistryOpen (2015)

Energy decomposition analysis for A“T” and a“t” at the equilibrium distance R(sp2) of A“T” and at the equilibrium distance R(sp3) of a“t”.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522182&req=5

fig09: Energy decomposition analysis for A“T” and a“t” at the equilibrium distance R(sp2) of A“T” and at the equilibrium distance R(sp3) of a“t”.
Mentions: The decomposition of the interaction energy is presented in graphical form in Figure 9 at the R(sp2) and R(sp3) distances. The augmentation of Pauli repulsion by compressing the dimers A“T” and a“t” from R(sp3) to the R(sp2) distance has to be overcome by the attractive contributions to the bonding energy. The electrostatic interaction gains for both dimers equally, and the dispersion correction does not change much by the compression. The largest difference due to the shortening is seen in the orbital interaction: A“T” gains more rapidly (blue line in ΔEoi) than a“t” (red line in ΔEoi). Decomposition of ΔEoi of A“T” into ΔEσ and ΔEπ of A“T” shows that it is the σ component in the orbital interaction (green line) that is responsible for strengthening the hydrogen bonds for the sp2-hybridized dimers, as it increases more rapidly. This results in an equilibrium structure of A“T” with shorter hydrogen bonds than for a“t”.

Bottom Line: In this study, we show quantum chemically that neither aromaticity nor other forms of π assistance are responsible for the enhanced stability of the hydrogen bonds in adenine-thymine (AT) DNA base pairs.Removing the aromatic rings of either A or T has no effect on the Watson-Crick bond strength.Bonding analyses based on quantitative Kohn-Sham molecular orbital theory and corresponding energy decomposition analyses (EDA) show that the stronger hydrogen bonds in the unsaturated model complexes and in AT stem from stronger electrostatic interactions as well as enhanced donor-acceptor interactions in the σ-electron system, with the covalency being responsible for shortening the hydrogen bonds in these dimers.

View Article: PubMed Central - PubMed

Affiliation: Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona 17071, Girona, Spain).

ABSTRACT
Hydrogen bonds play a crucial role in many biochemical processes and in supramolecular chemistry. In this study, we show quantum chemically that neither aromaticity nor other forms of π assistance are responsible for the enhanced stability of the hydrogen bonds in adenine-thymine (AT) DNA base pairs. This follows from extensive bonding analyses of AT and smaller analogs thereof, based on dispersion-corrected density functional theory (DFT). Removing the aromatic rings of either A or T has no effect on the Watson-Crick bond strength. Only when the smaller mimics become saturated, that is, when the hydrogen-bond acceptor and donor groups go from sp (2) to sp (3), does the stability of the resulting model complexes suddenly drop. Bonding analyses based on quantitative Kohn-Sham molecular orbital theory and corresponding energy decomposition analyses (EDA) show that the stronger hydrogen bonds in the unsaturated model complexes and in AT stem from stronger electrostatic interactions as well as enhanced donor-acceptor interactions in the σ-electron system, with the covalency being responsible for shortening the hydrogen bonds in these dimers.

No MeSH data available.