Spin trapping of radicals

Spin trapping of radicals generated by ultrasound (sonolysis) 126... 

Nucleic Acids. - Recent EPR studies of radical attack and formation upon DNA are reported elsewhere in this volume, by Sevilla and Becker, and therefore will not be described here in any detail. Findings of particular biomedical relevance include the spin trapping of radicals resulting from the decomposition of chloramines formed in the reaction of HOC1 with polynucleosides, RNA and... 

During 1985, Halpern and Knieper isolated and tentatively identified the tert-butoxy radical by the spin trapping of radicals in the vapor phase of cigarette smoke (27A44). 

Halpem, A. and J. Knieper Spin trapping of radicals in gas-phase cigarette smoke Z. Naturforsch. 40 (1985) 850-852. 

Rosen, G.M., Rauckman, E.J. and Finkelstein, E. Spin trapping of radical species in the propagation of lipid peroxidation, in Autoxidation in Food and Biological Systems, pp. 71-87 (1980), (edited by M.S. Simic and M. Karel) Plenum Press, New York. 

L. S. Benner and A. Balch, J. Organometallic Chem., 1977, 134, 121. Spin trapping of radicals produced by thermolysis of [Mn2L2(CO)g]. 

Albano, E., Tomasi, A., Goria-Gatti, L. and Dianzani, M.U. (1988). Spin trapping of free radical species produced during the microsomal metabolism of ethanol. Chem. Biol. Interact. 65, 223-234. 

Lai, E.K., Crossley, C., Sridhar, R., Misra, H.P., Janzen, E.G. and McCay, P.B. (1986). / wro spin-trapping of free radicals generated in brain, spleen, and liver during gamma radiation of mice. Arch. Biochem. Biophys. 244, 156-160. 

Spin trapping of short-lived radical species formed during... 

Spin trapping has been widely used for superoxide detection in various in vitro systems [16] this method was applied for the study of microsomal reduction of nitro compounds [17], microsomal lipid peroxidation [18], xanthine-xanthine oxidase system [19], etc. As DMPO-OOH adduct quickly decomposes yielding DMPO-OH, the latter is frequently used for the measurement of superoxide formation. (Discrimination between spin trapping of superoxide and hydroxyl radicals by DMPO can be performed by the application of hydroxyl radical scavengers, see below.) For example, Mansbach et al. [20] showed that the incubation of cultured enterocytes with menadione or nitrazepam in the presence of DMPO resulted in the formation of DMPO OH signal, which supposedly originated from the reduction of DMPO OOH adduct by glutathione peroxidase. 

Schreiber, J., Eling, T. E. and Mason, R. P. The oxidation of arachidonic acid by the cyclooxygenase activity of purified prostaglandin H synthase spin trapping of a carbon-centered free radical intermediate. Arch. Biochem. Biophys. 249 126-136,1986. 

A more recent example is found in the work of Schmid and Ingold (1978), who used the rate of rearrangement (17) of 5-hexenyl radicals into cyclopentylmethyl radicals (R- and R - in Scheme 5) to time the spin trapping of primary alkyl radicals. In this system, both R and R are primary alkyl, and their spin adducts with several traps therefore have virtually indistinguishable spectra. This difficulty was circumvented by labelling C-l in the hex-5-enyl radical with 13C the unrearranged radical then gives spin... 

Rate constants for spin trapping of alkyl radicals measured by the procedures outlined here, are collected with other spin-trapping rate data in Table 5. It will be seen that most nitrone and nitroso traps scavenge reactive radicals of diverse types with rate constants generally in the range 10s-10 1 mol-1 s l. Of the nitroso-compounds, the nitroso-aromatics (except for the very crowded TBN) are particularly reactive, whilst MBN and DMPO are the most reactive nitrones. Much of the data for spin trapping by nitrones has been accumulated by Janzen and his colleagues, who have discussed in a short review how steric and electronic factors influence these reactions (Janzen et ai, 1978). 

Approximate second order rate constants for spin trapping of reactive radicals ... 

Spin trapping of the superoxide radical anion, as well as that of hydroperoxyl and hydroxyl radicals and related species will be considered later in connection with biological chemistry (pp. 52-54). 

Experiments designed to utilize spin trapping to monitor free-radical chemistry in the gas phase were first reported by Janzen and Gerlock (1969). In these, radicals generated by photolysis in a stream of carrier gas were passed over solid PBN. The PBN was then dissolved in benzene, and the solution was found to contain spin adducts of radicals present in the gas stream. Photolysis of t-butyl hypochlorite vapour in this way leads to a nitroxide whose spectrum reveals splitting from two chlorine atoms. This proved to be due to butyl nitroxide (Janzen, 1971 Janzen et al., 1970), and recalls the observation of other nitroxides which apparently result from further reaction of the initial spin adducts. 

E. Albano, A. Tomasi, Spin Trapping of Free Radical Intermediates Produced during the Metabolism of Isoniazid and Iproniazid in Isolated Hepatocytes, Biochem. Pharmacol. 1987, 18, 2913-2920. 

Nitroso compounds, nitrones, and other diamagnetic molecules are used as spin traps. Capturing radicals prodnced in the reaction, spin traps form the so-called spin adducts—stable nitroxyl radicals easily detectable by ESR spectroscopy. In other words, the progress of the reaction can easily be followed by an increasing intensity of the spin-adduct signal. By and large, the method of traps reveals radicals by the disappearance (or appearance) of the ESR signal. 

Lai EK, McCay PB, Noguchi T, et al. 1979. In wVo spin-trapping of trichloromethyl radicals formed from Carbon tetrachloride. Biochem Pharmacol 28 2231-2235. 

Poyer JL, Floyd RA, McCay PB, etal. 1978. Spin-trapping of the trichloromethyl radical produced during enzymic NADPH oxidation in the presence of carbon tetrachloride or bromotrichloromethane. Biochim Biophys Acta 539 402- 409. 

Reinke LA, Towner RA, Janzen EG. 1992. Spin trapping of free radical metabolities of carbon tetrachlorie in vitro and in viva Effect of acute ethanol administration. Toxicol AppI Pharmacol 112 17-23. 

Spin Trapping of Carbon Radical Intermediate 63b C — N Bond Formation using DBNBS... 

Cheletrophic spin trapping of nitric oxide. Ultraviolet light converts the phenolic compound to a biradical, which rapidly reacts with nitric oxide to form a stable nitroxyl radical that is readily observable by electron paramagnetic resonance. 

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