A theoretical study of 5-halouracils: electron affinities, ionization potentials and dissociation of the related anions

Wetmore, Stacey D.; Boyd, Russell J.; Eriksson, Leif A.

doi:10.1016/s0009-2614(01)00652-2

Cited by 116 publications

(129 citation statements)

References 21 publications

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“…A large amount of experimental [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and theoretical work has been carried out in order to elucidate the structure of cytosine and its tautomers. Chemically modified bases have attracted extensive interest due to their numerous pharmacological, biochemical, and biological capabilities [59][60][61][62]. Replacing 2 ISRN Physical Chemistry nitrogen in pyrimidine and purine DNA bases by the biological element of interest, phosphorus, may produce new synthesizable bases of special interest.…”

Section: Introductionmentioning

confidence: 99%

Structure and Stability of Chemically Modified DNA Bases: Quantum Chemical Calculations on 16 Isomers of Diphosphocytosine

Al‐Sehemi

El-Gogary

Wolschann

et al. 2013

ISRN Physical Chemistry

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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 as PC3 = 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.

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Section: Introductionmentioning

confidence: 99%

Structure and Stability of Chemically Modified DNA Bases: Quantum Chemical Calculations on 16 Isomers of Diphosphocytosine

Al‐Sehemi

El-Gogary

Wolschann

et al. 2013

ISRN Physical Chemistry

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“…Medidas do espectro de transmissão eletrônica realizadas para as 5-halouracilas apontam para a existência de ressonâncias nesses sistemas [43], enquanto cálculos de estrutura eletrônica mostram para a existência de um estado ligado [44,45]. As seções de choque de dissociação são ordens de grandeza mais elevadas nas 5-halouracilas do que na uracila ou timina, além de apresentar um espectro de fragmentos muito mais rico [46][47][48][49][50][51].…”

Section: Estados Doânionunclassified

“…Nas 5-halouracilas, fragmentos são observados já a partir de 0 eV, o que indica que as reações de dissociação correspondentes devem ser endotérmicas. Esseé um dos principais aspectos que carecem de uma melhor compre-ensão, uma vez que os cálculos existentes [44,45,48,134] riam surgir a partir da captura do elétron por fragmentos gerados da degradação térmica da molécula neutra, embora essa não deva ocorrer na faixa de temperaturas em que as mediadas foram realizadas [48]. A possibilidade usualmente mais creditadaé a de captura eletrônica em bandas vibracionalmente quentes da molécula alvo, onde a energia térmica adicional daria conta de reduzir o threshold de dissociação [48].…”

Section: Cs Oânion [Tu−h]unclassified

“…eV abaixo de cálculos anteriores [44,45,48,134], para todas as 5-halouracilas. Considerando que essa estabilizaçãoé superior ao desvio absoluto médio reportado para o método Um dos aspectos mais intrigantes sobre os dados de dissociação das 5-halouracilaś e a ausência do sinal de eliminação de hidrogênio na 5-bromouracila e 5-iodouracila, em contraste aos casos da uracila, 5-fluorouracila e 5-clorouracila.…”

Section: Cs Oânion [Tu−h]unclassified

“…Nessa energia, oátomo do hidrogênio elimi- eV, sem correção de energia de ponto zero, próxima dos valores existentes de 0,45 eV [44] e 0,37 eV [45]. Em todos os sistemas, a curvatura do potencial doânion adiabáticoé menor do que a do neutro, na vizinhança do equilíbrio da espécie neutra, e por isso a A medida que o halogênioé afastado de sua posição de equilíbrio, ocorrem uma sequência de mudanças estruturais (ver figura 4.27) e no caráter e energética doânion adiabático.…”

Section: Cs Oânion [Tu−h]unclassified

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Dinâmica de íons temporários de biomoléculas halogenadas

Kossoski¹

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We present results on the anion spectrum and on the vibrational dynamics induced by electron capture, for a series of halogenated molecules. The anion states were characterized by means of elastic scattering calculations, in the fixed nuclei approximation, performed with the Schwinger multichannel method with pseudopotentials. Quantum dynamics calculations of the nuclear wavepacket were performed by the propagation on potential energy surfaces described in the local approximation. The target molecules comprise chloromethane, chloroethene, uracil, 5-fluorouracil, 5-chlorouracil, 5-bromouracil, 5-iodouracil, 6-chlorouracil, 2-thiouracil, adenine, 2-chloroadenine and 8-chloroadenine. For chloromethane we computed vibrational excitation cross sections for the C−Cl stretching, and showed this mode is promptly activated by the presence of the extra charge. For chloroethene, we demonstrated that the direct mechanism of dissociation is very inefficient, and also revealed the interesting topology of its complex potential energy surfaces. The derivatives of uracil presented rich anionic spectra, as each one has three π * delocalized states, a σ * state located at the bond between the substituted atom and the ring, and a dipole bound state. Overall, the obtained energetics are in very good agreement with experimental data. Analysis of the anionic spectra and the potential energy surfaces indicate mechanisms in which the anion is formed in a long-lived π * resonance and changes its character to the dissociative σ * state. For 5-chlorouracil in particular, this coupling is mediated by an out-of-plane movement of the chlorine atom. As the anion states progressively stabilize as the halogen atomic number increases, the couplings become more favorable, and account for the increasing dissociation cross sections. Our results explain many of the observed features of dissociative electron attachment to halouracils, providing a theoretical basis for its radiosensitizing ability. In chloroadenines, we found a σ * resonance and four π * resonances. We support they could also act as potential radiosensitizers.

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