A study of oxygen- versus hydrogen peroxide-supported activation of iron.cntdot.bleomycin

Thermodynamics and kinetics of the cleavage of DNA catalyzed by bleomycin A5

“…In Table 4, we compared the molar enthalpy change for the cleavage of calf thymus DNA induced by BLM-A 5 with those for the scission of calf thymus DNA mediated by two well-known DNA-damaging agents, ADM [39,40] and (1,10-phenanthroline)-copper [31,32]. Scission of calf thymus DNA induced by BLM in the presence of Fe 2+ and O 2 , converted calf thymus DNA to free nucleic bases [2,5,13,14].…”

“…Both Fe 2+ and O 2 serve as cofactors in DNA cleavage by BLM [2][3][4][5][6]. When ferrous BLM is exposed to O 2 , a transient complex of drug, iron and oxygen, which is kinetically competent to initiate DNA degradation and commonly termed activated BLM, is formed [2,4,5,13,14,16,18,46]. Nakamura & Peisach [47] have suggested that the bithiazloe structure of BLM-A 2 is altered when it is inactivated.…”

“…It has been found that BLM-induced autoxidation of ferrous iron follows the Michaelis-Menten kinetics [9,10]. Although a significant number of experimental approaches have been used to elucidate the mechanism of DNA cleavage by BLM in the past two decades [2][3][4][5][6][11][12][13][14][15][16][17][18][19][20], thermodynamic information for the scission, which is necessary for a thorough understanding of the mechanism, is eagerly awaited. The purpose of this investigation is to provide detailed thermodynamic and kinetic data for BLMmediated DNA degradation to furnish insights into the anticancer mechanism of BLM.Microcalorimetry is an important tool for the study of both thermodynamic and kinetic properties of biological macromolecules by virtue of its general applicability, high accuracy and precision [21][22][23][24].…”

Potentiometric sensing of nuclease activities and oxidative damage of single-stranded DNA using a polycation-sensitive membrane electrode

“…Therefore, extensive efforts have been made to measure the damage of DNA by reactive oxygen species. The same methods as for enzymatic cleavage are presently available, including but not limited to gel electrophoresis, HPLC, fluorescence resonance energy transfer techniques based on doubly labeled DNA probes (Fitzsimons and Barton, 1997;Natrajan et al, 1990;Hashimoto et al, 2001), and direct visualization via gold nanoparticles or conjugated polymers (Tang et al, 2006;Shen et al, 2009). There is still a significant interest in seeking more sensitive and convenient strategies for sensing the cleavage of DNA by ROS.…”

Ascorbate both activates and inactivates bleomycin by free radical generation

“…The activated BLM, H02--Fe111BLM, is highly oxidizing. It can abstract H' from DNA (Petering et al, 1990;Stubbe & Kozarich, 1987;Hecht, 1986), thereby initiating DNA strand scission, generate 'OH radicals (Oberley & Buettner, 1979;Solaiman et al, 1979;Sugiura & Kikuchi, 1978;Antholine et al, 1991), homolytically cleave hydroperoxides (Padbury et al, 1988), produce thiyl radicals from thiols (Antholine et al, 1991;, and oxidize HEPES to free radical products (Antholine et al, 1991).…”