Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 4

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Ionisation potential and electron affinity of free 5′,8-cyclopurine-2′-deoxynucleosides. DFT study in gaseous and aqueous phase

100%
Karwowski B.
Open Chemistry
|
2010
|
vol. 8
|
issue 1
70-76
EN
Oxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts it was decided to present, for the first time, the electron affinity, ionization potential of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The zero-point vibrational corrected adiabatic electron affinity (AEA) and adiabatic ionization potential (AIP) were calculated. Additionally the vertical electron affinity (VEA), vertical detachment energy (VDE) and vertical ionization potential were taken into consideration. AEA in eV (gaseous/aqueous phase) are as follows: 0.3/1.81 (5′R)cdA, 0.13/1.76 (5′S)cdA, 0.17/1.49 (5′R)cdG, 0.14/1.53 (5′S)cdG and AIP followed the order 7.43/5.59(5′S)cdG, 7.49/5.60(5′R)cdG, 7.77/5.97(5′R)cdA, 7.84/5.93(5′S)cdA. The obtained AIPs were found to be lower than that for corresponding natural nucleosides. Therefore, even though the 5′,8-cyclopurine-2′-deoxynucleoside level in a cell was judged as low, they can play an important role in the stability, replication and transcription of genes. [...]
2
Content available remote

The difference in stability between 5′R and 5′S diastereomers of 5′,8-cyclopurine-2′-deoxynucleosides. DFT study in gaseous and aqueous phase

100%
Karwowski B.
Open Chemistry
|
2010
|
vol. 8
|
issue 1
134-141
EN
Oxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts it has been decided to calculate the stability of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The calculations showed a significant negative enthalpy for glycosidic bond cleavage reaction for cationic forms and slightly negative for neutral ones. The preliminary study of the discussed process has shown the nature of stepwise nucleophilic substitution DN*AD type mechanism. Surprisingly, the different values in free energy, between short-lived oxacarbenium ion intermediates, have been found to lie over a relatively small range, around 1 and 2.8 kcal mol−1. For anions, the decomposition enthalpies were found as positive in aqueous phases. These theoretical results are supported by the formic acid hydrolysis experiments of both diastereomers of cdA, for the first time. (5′S)cdA exhibited higher stability than (5′R)cdA. [...]
3
Content available remote

The influence of (5′R) and (5′S)-5′,8-cyclo-2′-deoxyadenosine for the electronic properties of nucleosides pairs. The theoretical quantum mechanics studies

100%
Karwowski B.
Open Chemistry
|
2013
|
vol. 11
|
issue 7
1079-1090
EN
Oxidatively generated damage to DNA frequently appears in the human genome as the effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents such as ionization radiation. In this paper, for the first time, the electronic properties of nucleoside pairs containing 5′,8-cyclo-2′-deoxyadenosine (cdA) in their 5′R and 5′S diastereomeric forms (cdA(R)::T and cdA(S)::T) as the simplest model of ds-DNA have been discussed. The following values of the selected electronic parameters, measured in eV, were found for cdA(R)::T, cdA(S)::T, and dA::T, respectively, adiabatic/vertical electron affinity: 0.39/0.24, 0.35/0.18, 0.33/0.21; and adiabatic/vertical ionization potential: 7.27/7.50, 7.7.25/7.49, 7.03/7.27. Moreover, based on the results of the relaxation energy, the presence of cdA(S)::T should provide the highest barrier for electron transfer in ds-DNA. Analyses of hydrogen bond length deviations reveal that the formation of cationic forms results in higher elongation than that of anionic forms. Moreover, during the electron attachment or detachment for the investigated cdA(R)::T, cdA(S)::T, and dA::T nucleoside pairs, the same scheme of changes in hydrogen bond length was noted. [...]
4
Content available remote

5',8-Cyclo-2'-deoxyadenosine (cdA) formation by γ-radiation. Theoretical quantum mechanics study

51%
Karwowski B., Grand A., Cadet J.
|
|
issue 4
655-662
EN
Reactions of reactive oxygen species and more specifically - of hydroxyl radical (•OH) - with nucleosides may lead to the generation of radicals in the base and 2-deoxyribose moieties. In the present study emphasis was put on the possible reaction modes of 2'-deoxyadenosine (dA) radicals, leading to the formation of related 5',8-cyclonucleosides. It appears that the prerequisite for the formation of 5',8-cyclo-2'-deoxyadenosine (cdA) is the adoption of O4'-exo conformation by 2-deoxyribose; however, this is the least energetically favored conformer among the different puckered forms adopted by the furanose ring. The O4'-exo conformation was found to be present in each of the discussed mechanisms.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.