Electron Spin Resonance Studies of 1:1:1 Bleomycin-Cobalt(II)-Qxygen Adduct Complex
Bleomycin has been used extensively in the chemotherapy and radiodiagnosis of cancer (1). One of the most important aspects of its chemistry is its ability to coordinate a variety of metals. Recently, bleomycin-metal complexes have attracted particular attention because of their interesting behavior: (i) the copper(II) complex is a metabolic form of bleomycin (2), (ii) γ-emitting metal complexes such as 57CO, 99mTc, and 111In have been investigated as a means of visualizing tumors(3), and (iii) an oxygen-labile iron(II) complex may play an important role in DNA degradation by bleomycin(4,5). Sausville et al. reported that the conversion of SV40 DNA to acid-soluble products occurs at approximately equimolar levels of Fe(II), bleomycin, and DNA(4). Takita et al. have proposed that an oxygen activated by the bleomycin-Fe(II) complex is involved in the action of bleomycin on DNA(5). Additionally, it has been suggested that superoxide radical is one of the chemical mediators responsible for the enhancement of DNA chain breakage by bleomycin (6). Herein, the 1:1 bleomycin A2-Co(II) complex and its oxygen adduct complexes have been characterized by electron spin resonance (ESR) spectroscopy; the present results should serve to facilitate an understanding of the degradation of DNA by the bleomycinFe(II)-02 complex.
KeywordsMicrowave EDTA Superoxide Adduct Schiff
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