TY  - THES
T1  - Electron spin resonance of free radicals formed from DNA and its constituents on X-ray irradiation : influence of matrices, additives, dose, temperature and time
T3  - The journal of physical chemistry / B. - 110. 2006, 30, 14976-14987, DOI: 10.1021/jp0583086
A1  - Pal,Chandrima
Y1  - 2009/03/24
N2  - Electron spin resonance (ESR) studies were performed on free radicals formed upon X ray irradiation on DNA, its constituents and model compounds like fluorouracil and its derivatives. One aim of this thesis was to understand the much debated mechanism of radical formation in irradiated frozen aqueous solutions of DNA. In things matrix, DNA separates from the bulk ice as an inhomogeneous mass and mimics biological conditions. Fluorouracil (FU) and its derivatives were used as model compounds utilizing the large fluorine hyperfine splitting as a tool of radical identification. Glassy low temperature matrices were employed for comparison with frozen aqueous solutions. Electron scavengers like Na2S2O8 and K3Fe[CN]6 were used to enhance the contribution of oxidized radicals. This study gave evidence of direct irradiation action in the frozen aqueous system. The study was extended to frozen aqueous solutions containing DNA; where irradiation dose as well as electron and hole scavengers were used to modulate the formation of radicals. From spectra reconstruction utilizing isolated component patterns the formation of sugar based radicals and guanine cation radicals at low temperatures were observed which supports the direct effect of irradiation. Another aim was to study the hypothesis of electron transfer from DNA anions to the doped additives in post irradiation time phase. Time dependent quantitative ESR studies were done on DNA and on its complexes with mitoxantrone and riboflavin, deoxy ribonucleotides of thymine and cytosine and their complexes with mitoxantrone in 7 M LiBr glass. No transfer of electrons was observed but differential decay behavior with time of the radicals on DNA and the additive, respectively, was found.
KW  - Elektronenspinresonanz
KW  - Röntgenbestrahlung
KW  - DNS
KW  - DNS-Reparatur
KW  - DNS-Schädigung
KW  - DNS-Doppelstrangbruch
KW  - Mitoxantron
CY  - Saarbrücken
PB  - Universitäts- und Landesbibliothek
AD  - Postfach 151141, 66041 Saarbrücken
UR  - http://scidok.sulb.uni-saarland.de/volltexte/2009/2083
ER  -