Reactivity of superoxide anion radical with a perchlorotriphenylmethyl (trityl) radical |
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Authors: | Kutala Vijay Kumar Villamena Frederick A Ilangovan Govindasamy Maspoch Daniel Roques Nans Veciana Jaume Rovira Concepció Kuppusamy Periannan |
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Affiliation: | Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA. |
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Abstract: | The reaction of superoxide radical with a tricarboxylate derivative of perchlorotriphenylmethyl radical (PTM-TC) is studied. PTM-TC is a stable ("inert") free radical, which gives a single sharp electron paramagnetic resonance (EPR) peak in aqueous solutions. PTM-TC also gives a characteristic optical absorption at 380 nm. Superoxide, on reaction with PTM-TC, induced a decrease in the intensity of the EPR signal and optical absorption of PTM-TC at 380 nm. The signal loss was specific to superoxide and linearly dependent on the superoxide flux in the system. Competitive kinetics experiments revealed that PTM-TC reacts with superoxide with an apparent second-order rate constant of 8.3x10(8) M(-1) s(-1). Electrochemical and mass spectrometric analyses of the reaction suggested the formation of perchlorotriphenylmethane and molecular oxygen as products. The high sensitivity of detection of PTM-TC combined with the high rate constant of the reaction of superoxide with PTM-TC may offer a potential opportunity for measurement of superoxide in biological systems. In conclusion, the PTM-TC molecule has high sensitivity and specificity for superoxide radicals and thus may enable quantitative detection of superoxide generation in biological systems using EPR and/or spectrophotometric methods. |
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