A DNA Oligonucleotide-Hemin Complex Cleaves t-Butyl Hydroperoxide through a Homolytic Mechanism
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- 作者：Paul K. Witting ; Paula Travascio ; Dipankar Sen ; and A. Grant Mauk
- 刊名：Inorganic Chemistry
- 出版年：2001
- 出版时间：September 10, 2001
- 年：2001
- 卷：40
- 期：19
- 页码：5017 - 5023
- 全文大小：78K
- 年卷期：v.40,no.19(September 10, 2001)
- ISSN：1520-510X
文摘
Both electron paramagnetic resonance (EPR) and electronic absorption spectroscopy have been employed toinvestigate the reaction of a guanine-rich DNA nucleotide-hemin complex (PS2.M-hemin complex) and organicperoxide (t-Bu-OOH). Incubation of the PS2.M-hemin complex with t-Bu-OOH resulted in the time-dependentdecrease in the heme Soret with concomitant changes to the visible bands of the electronic absorbance spectrumfor the PS2.M-hemin complex. Parallel EPR studies using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO)combined with spectral simulation demonstrated the presence of tert-butyloxyl, carbon-centered methyl, and methylperoxyl radicals as well as a simple nitroxide (triplet) signal. Experiments, performed by maintaining a constantratio of t-Bu-OOH/PS2.M-hemin complex (~35 mol/mol) while varying DMPO concentration, indicated thatthe relative contributions of each radical adduct to the composite EPR spectrum were significantly influenced bythe DMPO concentration. For example, at DMPO/PS2.M-hemin of 10-50 mol/mol, a complex mixture of radicalswas consistently detected, whereas at high trapping efficiency (i.e., DMPO/PS2.M-hemin of ~250 mol/mol) thetert-butyloxyl-DMPO adduct was predominant. In contrast, at relatively low DMPO/PS2.M-hemin complexratios of 
5 mol/mol, a simple nitroxide three-line EPR signal was detected largely in the absence of all otherradicals. Together, these data indicate that tert-butyloxyl radical is the primary radical likely formed from thehomolytic cleavage of the O-O peroxy bond of t-Bu-OOH, while methyl and methyl peroxyl radicals resultfrom 
-scission of the primary tert-butyloxyl radical product.
5 mol/mol, a simple nitroxide three-line EPR signal was detected largely in the absence of all otherradicals. Together, these data indicate that tert-butyloxyl radical is the primary radical likely formed from thehomolytic cleavage of the O-O peroxy bond of t-Bu-OOH, while methyl and methyl peroxyl radicals resultfrom -scission of the primary tert-butyloxyl radical product.