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Structure and singly occupied molecular orbital analysis of anionic tautomers of guanine

Haranczyk, M., Holliday, J.D., Willett, P. and Gutowski, M. (2008) Structure and singly occupied molecular orbital analysis of anionic tautomers of guanine. Journal of Computational Chemistry, 29 (8). pp. 1277-1291. ISSN 0192-8651

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Recently we reported the discovery of adiabatically bound anions of guanine which might be involved in the processes of DNA damage by low-energy electrons and in charge transfer through DNA. These anions correspond to some tautomers that have been ignored thus far. They were identified using a hybrid quantum mechanical-combinatorial approach in which an energy-based screening was performed on the library of 499 tautomers with their relative energies calculated with quantum chemistry methods.

In the current study we analyze the adiabatically bound anions of guanine in two aspects: 1) the geometries and excess electron distributions are analyzed and compared with anions of the most stable neutrals to identify the sources of stability; 2) the chemical space of guanine tautomers is explored to verify if these new tautomers are contained in a particular subspace of the tautomeric space. The first task involves the development of novel approaches – the quantum chemical data like electron density, orbital and information on its bonding/antibonding character are coded into holograms and analyzed using chemoinformatics techniques. The second task is completed using substructure analysis and clustering techniques performed on molecules represented by 2D fingerprints.

The major conclusion is that the high stability of adiabatically bound anions originates from the bonding character of the pi orbital occupied by the excess electron. This compensates for the antibonding character that usually causes significant buckling of the ring. Also the excess electron is more homogenously distributed over both rings than in the case of anions of the most stable neutral species. In terms of 2D substructure, the most stable anionic tautomers generally have additional hydrogen atoms at C8 and/or C2 and they don’t have hydrogen atoms attached to C4, C5 and C6. They also form an “island of stability” in the tautomeric space of guanine.

Item Type: Article
Copyright, Publisher and Additional Information: © 2007 Wiley Periodicals, Inc. This is an author produced version of a paper accepted for publication in Journal of Computational Chemistry. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: anions of nucleic acid bases, guanine, tautomers, substructural analysis, tautomeric space
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Social Sciences (Sheffield) > Information School (Sheffield)
Depositing User: Repository Officer
Date Deposited: 28 Jan 2008 19:23
Last Modified: 08 Feb 2013 16:55
Published Version: http://dx.doi.org/10.1002/jcc.20886
Status: Published
Publisher: John Wiley
Refereed: Yes
Identification Number: 10.1002/jcc.20886
URI: http://eprints.whiterose.ac.uk/id/eprint/3601

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