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1.
J Phys Chem A ; 111(39): 9823-9, 2007 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-17760432

RESUMO

The binding of first-row transition metal monocations (Sc+-Cu+) to N7 of guanine and N7 or N3 of adenine nucleobases has been analyzed using the hybrid B3LYP density functional theory (DFT) method. The nature of the bonding is mainly electrostatic, the electronic ground state being mainly determined by metal-ligand repulsion. M+-guanine binding energies are 18-27 kcal/mol larger than those of M+-adenine, the difference decreasing along the row. Decomposition analysis shows that differences between guanine and adenine mainly arise from Pauli repulsion and the deformation terms, which are larger for adenine. Metal cation affinity values at this level of calculation are in very good agreement with experimental data obtained by Rodgers et al. (J. Am. Chem. Soc. 2002, 124, 2678) for adenine nucleobases.


Assuntos
Adenina/química , Cátions , Físico-Química/métodos , Guanina/química , Metais/química , Cobre/química , Eletrônica , Elétrons , Íons , Espectrometria de Massas , Modelos Químicos , Modelos Moleculares , Modelos Teóricos , Conformação Molecular , Eletricidade Estática
2.
J Phys Chem B ; 110(11): 5767-72, 2006 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-16539523

RESUMO

The influence of oxidation, protonation, and metal cationization with Cu(+) and Cu(2+) on the strength of the N-glycosidic bond in 2'-deoxyguanosine has been studied by means of quantum chemical calculations. In all cases, the N9-C1' bond distance increases (0.03-0.06 A) upon introducing positive charge in the guanine moiety, the observed variations being more important for the dicationic systems. Binding energies show that the effect of X(n)(+) in guanine hinders the homolytic dissociation, whereas it largely favors the heterolytic process. With respect to the deoxyribose ring, it has been found that metal binding, oxidation, and protonation do not significantly change the values of the phase angle of pseudorotation P. However, the glycosyl torsion angle chi varies considerably (from 242.0 degrees to 189.8 degrees) as a consequence of a stabilizing guanine-sugar (H8-O4') interaction due to the increase of acidity of guanine C8-H8 upon cationization.


Assuntos
Desoxiguanosina/química , Glicosídeos/química , Íons , Metais/química , Prótons , Algoritmos , Sítios de Ligação , Desoxiguanosina/metabolismo , Glicosídeos/metabolismo , Guanina/química , Modelos Moleculares , Estrutura Molecular , Oxirredução , Teoria Quântica
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