Journal of Chemical Sciences

, Volume 112, Issue 4, pp 487–496 | Cite as

Quenching of nucleotide-derived radicals bybisbenzimidazole derivative Hoechst-33258 in aqueous solution



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.


Nucleotide-derived radicals Hoechst-33258 pulse radiolysis 


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Copyright information

© Indian Academy of Sciences 2000

Authors and Affiliations

  • H. Mohan
    • 1
  • A. Adhikary
    • 2
  • V. Jain
    • 2
  • J. P. Mittal
    • 1
    • 3
  1. 1.Radiation Chemistry and Chemical Dynamics DivisionBhabha Atomic Research CentreMumbaiIndia
  2. 2.Department of BiocyberneticsInstitute of Nuclear Medicine and Allied SciencesDelhiIndia
  3. 3.Jawaharlal Nehru Centre for Advanced Scientific ResearchBangaloreIndia

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