Structure and Stability of Chemically Modified DNA Bases: Quantum Chemical Calculations on 16 Isomers of Diphosphocytosine. (25th February 2013)

• Record Type: Journal Article
• Authors: Al-Sehemi, Abdullah G.; El-Gogary, Tarek M.; Wolschann, Karl Peter; Koehler, Gottfried
• Other Names: Starikov E. B. Academic Editor.; Tilocca A. Academic Editor.
• Is Part Of: ISRN physical chemistry. Volume 2013(2013)
• Publication Date: 2013-02-25
• Subjects: Chemistry, Physical and theoretical -- Periodicals; Chemistry, Physical and theoretical; 35.10 physical chemistry: general; Periodicals; Electronic journals; 541
• DOI: 10.1155/2013/146401
• Languages: English
• ISSNs: 2090-7761

Abstract

Abstract : We studied for the first time 16 tautomers/rotamers of diphosphocytosine by four computational methods. Some of these tautomers/rotamers are isoenergetic although they have different structures. High-level electron correlation MP2 and MP4(SDQ) ab initio methods and density functional methods employing a B3LYP and the new M06-2X functional were used to study the structure and relative stability of 16 tautomers/rotamers of diphosphocytosine. The dienol tautomers of diphosphocytosine are shown to be much more stable than the keto-enol and diketo forms. The tautomers/rotamers stability could be ranked asPC3 = PC12 < PC2 = PC11 < PC1 < PC10 < PC8 < PC9 < PC15 < PC16 < PC6 ~ PC7 < PC13 < PC4 ~ PC14 < PC5 . This stability order was discussed in the light of stereo and electronic factors. Solvation effect has been modeled in a high dielectric solvent, water using the polarized continuum model (PCM). Consideration of the solvent causes some reordering of the relative stability of diphosphocytosine tautomers:PC3 ~ PC12 ~ PC2 ~ PC11 < PC1 < PC10 < PC8 < PC9 < PC15 ~ PC16 < PC13 < PC6 ~ PC7 ~ PC14 < PC4 ~ PC5 .