Oxidation-Reduction Reactions of Iron Bleomycin in the Absence and Presence of DNA |
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Authors: | Sara Goldstein Gidon Czapski |
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Affiliation: | a Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel |
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Abstract: | Using the pulse radiolysis technique, we have demonstrated that bleomycin-Fe(III) is stoichiometrically reduced by CO2- to bleomycin-Fe(II) with a rate of (1.9 ± 0.2) × 108M-1s-1. In the presence of calf thymus DNA, the reduction proceeds through free bleomycin-Fe(III) and the binding constant of bleomycin-Fe(III) to DNA has been determined to be (3.8 ± 0.5) x 104 M-1. It has also been demonstrated that in the absence of DNA O2-1 reacts with bleomycin-Fe(III) to yield bleomycin-Fe(II)O2, which is in rapid equilibrium with molecular oxygen, and decomposes at room temperature with a rate of (700 ± 200) s-1. The resulting product of the decomposition reaction is Fe(III) which is bound to a modified bleomycin molecule. We have demonstrated that during the reaction of bleomycin-Fe(II) with O2, modification or self-destruction of the drug occurs, while in the presence of DNA no destruction occurs, possibly because the reaction causes degradation of DNA. |
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Keywords: | Bleomycin Iron DNA Damage Radiolysis Superoxide CO2- |
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