Quenching of nucleotide-derived radicals by bis benzimidazole derivative Hoechst-33258 in aqueous solution |
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Authors: | H Mohan A Adhikary V Jain and J P Mittal |
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Institution: | (1) Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Trombay, 400 085 Mumbai, India;(2) Department of Biocybernetics, Institute of Nuclear Medicine and Allied Sciences, Lucknow Marg, 110 054 Delhi, India;(3) Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India |
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Abstract: | The pulse radiolysis technique has been employed to investigate the reaction of DNA-minor-groove ligand bisbenzimidazole Hoechst
33258 with pyrimidine and purine nucleotide-derived radicals. Formation of an N-centred Hoechst-33258 radical is observed.
Bimolecular rate constants and the yields of Hoechst-33258 radical have been evaluated. While the rate constant for the reaction
of pyrimidine-derived radicals with Hoechst-33258 remained the same (1–2) × 109 dm3 mol−1 s−1, the yields of the Hoechst-33258 radical varied from 25% (5′-cytidine monophosphate) to 75% (5′-guanosine monophosphate)
under anoxic conditions. The rate constant values for the reaction of purine-derived radicals with Hoechst-33258, under oxic
and anoxic conditions, remained the same whereas with pyrimidine-derived radicals, the rate constant value under oxic conditions
was about two orders of magnitude lower than under anoxic conditions. The difference in the yields of Hoechst-33258 radical
with various nucleotide-derived radicals suggest the formation of different types of radicals and that the reaction mainly
occurs by electron transfer from Hoechst-33258 to the nucleotide radicals. |
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Keywords: | Nucleotide-derived radicals Hoechst-33258 pulse radiolysis |
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