A molecular orbital analysis of the DNA bases

Leão, Marcelo Brito Carneiro; Longo, Ricardo L.; Pavão, Antonio C.

doi:10.1016/s0166-1280(99)00095-0

Cited by 13 publications

(11 citation statements)

References 18 publications

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“…They also include the 7H-anti-hydroxo-amino-tautomer, which has not been investigated earlier. [11][12][13] However, this form should be less favored because of steric interactions. Indeed, according to our pilot calculations, 7H-anti-hydroxo-amino-guanine has been found to lie by more than 10 kcal/mol higher than the lowest-energy tautomer of guanine.…”

Section: Methodsmentioning

confidence: 99%

Thermodynamics and Kinetics of Intramolecular Proton Transfer in Guanine. Post Hartree−Fock Study

et al. 2005

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The most stable tautomers and rotamers of guanine are characterized by post Hartree-Fock ab initio calculations at the MP2 and CCSD(T) levels employing extended basis sets. Four of the lowest-energy structures (7H-oxo-amino- < 9H-oxo-amino- < 9H-syn-hydroxo-amino- < 9H-anti-hydroxo-amino-guanine) are found to lie within ca. 1 kcal/mol. The next form of guanine is established to lie more than 3 kcal/mol higher than the global minimum tautomer. The transition states of the following reversible reactions: 9H-oxo-amino-guanine right harpoon over left harpoon 9H-syn-hydroxo-amino-guanine right harpoon over left harpoon 9H-anti-hydroxo-amino-guanine have been studied. The calculated energy data were used to obtain thermodynamic parameters and to estimate the composition of the equilibrium mixture of conformers at 0 K and room temperature. The rate constants for the tautomerization of 9H-oxo-amino-guanine were determined by using the instanton approach. Their predicted values characterize an extremely slow chemical process, which is expected to reach the equilibrium in ca. 2500 h. Despite being so slow, we have shown that such a rate of the tautomerization describes a process that is much faster than the one characterized by the observed frequency of spontaneous point mutations. Therefore, additional stabilization factors, e.g., hydrations and interactions with enzymes are necessary to secure the known fidelity of DNA synthesis.

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Section: Methodsmentioning

confidence: 99%

Thermodynamics and Kinetics of Intramolecular Proton Transfer in Guanine. Post Hartree−Fock Study

et al. 2005

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“…One of the earliest attempts at theoretical resolution of adenine PES was through a semiempirical AM1 variant of the restricted open‐shell Hartree‐Fock (HF) and Outer Valence Green's function (OVGF) approaches that were used to get vertical and adiabatic ionization energies of a selected few tautomers of the adenine DNA base 40. Guerra et al 38 computed vertical and adiabatic first ionization energies of 12 adenine tautomers with BP86/TZ2P and BP86/QZ4P levels of density functional theory (DFT).…”

Section: Introductionmentioning

confidence: 99%

“…Of the many tautomers of nucleic acid bases, those belonging to adenine have received particularly detailed attention since these tautomeric variants provide a structurally and energetically easy fit for mutagenic pairing with cytosine and thymine 37, 38. As usual, the ionization potential being a critical discriminant of reactivity, experimental determination 27–35, and theoretical calculation 33, 37–45 of ionization energies of adenine tautomers have seen much recent activity. Photoelectron spectra (PES) of the canonical adenine base have been reported by many researchers 27–35 and some of the complications in the assignment of peaks have been attributed to the presence of possible tautomers 33, 40.…”

Section: Introductionmentioning

confidence: 99%

Tautomeric forms of adenine: Vertical ionization energies and Dyson orbitals

Singh¹,

Ortiz²,

Mishra³

2009

Int J of Quantum Chemistry

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ABSTRACT:For the MP2/6-311ϩϩg(2df,p) optimized geometry of all the 14 adenine tautomers, the first three vertical ionization energies have been calculated using several electron propagator decouplings. The corresponding Dyson orbitals provide detailed insight into the role of structural variations in different adenine tautomers. Changes in the electron binding energies and the corresponding Dyson orbital amplitudes have been correlated with tautomeric proton shifts and changes in conjugation patterns.

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“…9 by 0.20–0.34 eV. A semiempirical AM1 variant of the outer valence Green's function was employed to obtain the first IE values of a number of isomers of DNA bases 10. ΔSCF AM1 values were published in the same work.…”

Section: Introductionmentioning

confidence: 99%