Electron paramagnetic resonance and ultraviolet/visible study of compounds I and II in the horseradish peroxidase–H2O2–silk fiber reaction system

Singlet molecular oxygen produced in the presence of 2,2,6,6-tetramethyl-4-piperidone (TMPD) in 1,4-dioxan, by boron subphthalocyanine chloride as the sensitizer, was monitored by Electron Paramagnetic Resonance (EPR) via the oxidation of TMPD to the corresponding aminoxyl radical. This radical product is formed in low yields along the singlet oxygen pathway. A kinetic analysis of the process allows one to understand the reasons behind this, while affording more accurate quantitative insights into the mechanistic details. A crucial aspect of this reaction system, which explains the low aminoxyl radical yields along the singlet oxygen pathway, is the disappearance of the sensitizer triplet state in a reaction with TMPD, which has a rate constant of 1 × 109 M-1.s-1.

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Electron Paramagnetic Resonance Detection of Free Tyrosyl Radical Generated by Myeloperoxidase, Lactoperoxidase, and Horseradish Peroxidase

Journal of Biological Chemistry ◽

10.1074/jbc.273.48.32030 ◽

1998 ◽

Vol 273 (48) ◽

pp. 32030-32037 ◽

Cited By ~ 62

Author(s):

Michael L. McCormick ◽

Joseph P. Gaut ◽

Tien-Sung Lin ◽

Bradley E. Britigan ◽

Garry R. Buettner ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Horseradish Peroxidase ◽

Tyrosyl Radical ◽

Paramagnetic Resonance ◽

Resonance Detection ◽

Electron Paramagnetic

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Electron-paramagnetic-resonance studies on a photochemically produced species of horseradish peroxidase compound I

Biochemical Journal ◽

10.1042/bj1670031 ◽

1977 ◽

Vol 167 (1) ◽

pp. 31-37 ◽

Cited By ~ 12

Author(s):

A R McIntosh ◽

M J Stillman

Keyword(s):

Electron Paramagnetic Resonance ◽

New Species ◽

Horseradish Peroxidase ◽

Room Temperature ◽

Resonance Signal ◽

Compound I ◽

Radical Species ◽

Strong Electron ◽

Paramagnetic Resonance ◽

Electron Paramagnetic

Strong electron-paramagnetic-resonance signals in the g = 2.00 region were detected after irradiation of horseradish peroxidase Compound I at temperatures of 10 and 100 K. These signals establish the presence of new free-radical species in the peroxidase system. The new species are interpreted in terms of a haem-photosensitized oxidation of the protein's peptide groups close to the Compound I radical site. On warming to room temperature, the radicals decayed irreversibly to a species having a weak asymmetric electron-paramagnetic-resonance signal at 100 K, which could still be observed after incubation at room temperature for more than 1 h.

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An electron paramagnetic resonance spectroscopic investigation of hydroxyl-radical attack on allyl alcohol

Canadian Journal of Chemistry ◽

10.1139/v67-106 ◽

1967 ◽

Vol 45 (6) ◽

pp. 649-654 ◽

Cited By ~ 24

Author(s):

P. Smith ◽

P. B. Wood

Keyword(s):

Electron Paramagnetic Resonance ◽

Hydroxyl Radical ◽

Allyl Alcohol ◽

Reaction System ◽

Alcohol Concentration ◽

Paramagnetic Resonance ◽

Relative Contribution ◽

Aqueous Flow ◽

Electron Paramagnetic ◽

Radical Attack

Allyl alcohol has been subjected to hydroxyl-radical attack at 25 ± 2 °C within the cavity of an X-band electron paramagnetic resonance (e.p.r.) spectrometer by use of an aqueous flow system in which the hydroxyl radicals were generated by mixing solutions of titanous chloride and hydrogen peroxide containing sulfuric acid. The reaction conditions were varied over a considerable range. At low allyl alcohol concentrations the e.p.r. absorption observed arose chiefly from the two possible addition products CH2(OH)CHCH2OH, I, and ·CH2CH(OH)CH2OH, II, present in roughly equal steady-state molar concentrations; a relatively weak signal from the hydrogen-atom abstraction product CH2:CHCHOH, III, was also observed. As the allyl alcohol concentration was raised, the relative contribution from I and II fell while that from the products of the addition of I and II to allyl alcohol became increasingly evident. These results considerably extend and clarify those previously reported for allyl alcohol by earlier workers using this reaction system.

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