Electron spin resonance , free

A85. Pryor, W.A. Biological effects of cigarette smoke, wood smoke, and smoke from plastics The use of electron spin resonance Free Radic. Biol. Med. 13 (1992) 659-676. 27A101. 

A122. Zang, L.Y., K. Stone, and W.A. Pryor Detection of free radicals in aqueous extracts of cigarette tar by electron spin resonance Free Radic. Biol. Med. 19 (1995) 161-167. 

Adrian F J 1971 Theory of anomalous electron spin resonance spectra of free radicals in solution. Role of diffusion-controlled separation and reencounter of radical pairs J. Chem. Rhys. 54 3918-23... 

Electron spin resonance (esr) (6,44) has had more limited use in coal studies. A rough estimate of the free-radical concentration or unsatisfied chemical bonds in the coal stmcture has been obtained as a function of coal rank and heat treatment. For example, the concentration increases from 2 X 10 radicals/g at 80 wt % carbon to a sharp peak of about 50 x 10 radicals/g at 95 wt % carbon content and drops almost to zero at 97 wt % carbon. The concentration of these radicals is less than that of the common functional groups such as hydroxyl. However, radical existence seems to be intrinsic to the coal molecule and may affect the reactivity of the coal as well as its absorption of ultraviolet radiation. Measurements from room... 

By using this technique acrylamide, acrylonitrile, and methyl acrylate were grafted onto cellulose [20]. In this case, oxidative depolymerization of cellulose also occurs and could yield short-lived intermediates [21]. They [21] reported an electron spin resonance spectroscopy study of the affects of different parameters on the rates of formation and decay of free radicals in microcrystalline cellulose and in purified fibrous cotton cellulose. From the results they obtained, they suggested that ceric ions form a chelate with the cellulose molecule, possibly, through the C2 and C3 hydroxyls of the anhy-droglucose unit. Transfer of electrons from the cellulose molecule to Ce(IV) would follow, leading to its reduction... 

For reviews of the use of ESR spectra to determine structures, see Walton, J.C. Rev. Chem. Intermed., 1984, 5, 249 Kochi, J.K. Adv. Free-Radical Chem., 1975, 5, 189. For ESR spectra of a large number of free radicals, see Bielski, B.H.J. Gebicki, J.M. Atlas of Electron Spin Resonance Spectra Academic Press NY, 1967. 

Evidence indicates [28,29] that in most cases, for organic materials, the predominant intermediate in radiation chemistry is the free radical. It is only the highly localized concentrations of radicals formed by radiation, compared to those formed by other means, that can make recombination more favored compared with other possible radical reactions involving other species present in the polymer [30]. Also, the mobility of the radicals in solid polymers is much less than that of radicals in the liquid or gas phase with the result that the radical lifetimes in polymers can be very long (i.e., minutes, days, weeks, or longer at room temperature). The fate of long-lived radicals in irradiated polymers has been extensively studied by electron-spin resonance and UV spectroscopy, especially in the case of allyl or polyene radicals [30-32]. 

KRISTENSEN D, krOger-ohlsen m V and SKIBSTED L H (2002) Radical formation in dairy products Prediction of oxidative stability based on electron spin resonance spectroscopy, in Morello M J, Shahidi F Ho CT Free Radicals in Food, Chemistry, Nutrition and Health Effects, ACS Symposium Series 807, Washington D C, 114-25. 

A number of the techniques that have been employed have the ability to directly monitor free-radical species either in vitro or in vivo [predominantly those involving electron spin resonance (e.s.r.) spectroscopy]. However, since many physiologically relevant free radicals have extremely short half-lives (e.g. 10 s for OH), the majority of the methods utilized detect products arising from their reactions with chemical components present (i.e. indirect methods). These indirect methods for... 

Garlick, P.B., Davies, M.J., Hearse, D.J. and Slater, T.F. (1987). Direct detection of free radicals in the reperfused rat heart using electron spin resonance spectroscopy. Circ. Res. 61, 757-760. 

Despite their short half-lives, it is possible to detect free radicals in biological tissues by the addition of nonradicals such as nitrones or nitroso compounds, which act as spin traps by forming relatively stable free radicals on reaction with the endogenous radical species. Utilizing the technique of electron spin resonance (e.s.r.) spectroscopy, we have demonstrated ROM generation by human rheumatoid synovium when subjected to cycles of hypoxia/normoxia in vitro. Using 3,5-dibromo-4-nitroso-benzenesulphonate (DBNBS) as a spin trap, a... 

Chemiluminescence has been used to demonstrate increased free-radical activity after induction of caerulein pancreatitis, with levels peaking at about 20 min and decreasing rapidly to control values thereafter (Gough et al., 1990). Electron spin resonance has been used to demonstrate increased hydroxyl radical activity in choline-deficient diet pancreatitis in the mouse (Nonaka etal., 1989a). 

X-Ray irradiation of quartz or silica particles induces an electron-trap lattice defect accompanied by a parallel increase in cytotoxicity (Davies, 1968). Aluminosilicate zeolites and clays (Laszlo, 1987) have been shown by electron spin resonance (e.s.r.) studies to involve free-radical intermediates in their catalytic activity. Generation of free radicals in solids may also occur by physical scission of chemical bonds and the consequent formation of dangling bonds , as exemplified by the freshly fractured theory of silicosis (Wright, 1950 Fubini et al., 1991). The entrapment of long-lived metastable free radicals has been shown to occur in the tar of cigarette smoke (Pryor, 1987). 

Jinno, J., Mori, H., Oshiro, Y., Kikuchi, T. and Sakurai, H. (1991). Evaluation of free radical scavenging activity of OPC-14117 by electron spin resonance technique. Free Rad. Res. Commun. 15, 223-230. 

Yoshikawa, T., Naito, Y., Tanigawa, T. and Kondo, M. (1993). Free radical scavei ng activity of the novel anti-ulcer agent rebamipide studied by electron spin resonance. Arzneim-Forsch. 43, 363-366. 

Mrad/h). Films were stored at -20° until analysis could be carried out. Oxidized films and derivatized, oxidized films were characterized by iodometry (reflux with Nal in isopropanol/acetic acid) and by transmission Fourier Transform (FT) IR (Perkin Elmer 1500), using the spectral subtraction technique (3, 14). Free radicals were measured by the electron spin resonance technique (e.s.r., Varian E4 spectrometer). 

Ribonucleotide reductase differs from the other 5 -deoxyadenosyl-cobalamin requiring enzymes in a number of respects. Hydrogen is transferred from coenzyme to the C2-position of the ribose moiety without inversion of configuration. Also since lipoic acid functions in hydrogen transfer, exchange with solvent protons takes place. Furthermore, exchange between free and bound 5 -deoxyadenosylcobalamin occurs rapidly during catalysis. Evidence for a Co(I)-corrin as an intermediate for this reduction is presented in our section on electron spin resonance. 

Another potentially very useful method of studying B 12-enzymes by electron spin resonance has been developed. This method involves attaching a stable organic free radical, in all cases studied so far a nitrox-... 

As with the nitroxalkylcobalamins (119) and cobinamides, the co-binamides in which nitroxide is coordinated show electron spin resonance spectra very similar to the spectrum of free nitroxide. The high field line is not broadened as much as in the spectrum of a nitroxalkyl-cobinamide. No hyperfine splitting from methyl protons in the 2 or 6 positions can be observed for the bound nitroxide. However, treatment of the coordinate spin labeled compounds with cyanide releases the nitroxide. When this happens, the proton hyperfine can be observed (Fig. 25). Thus treatment with cyanide simply displaces the nitroxide and a spectrum for free nitroxide is observed. 

The electron spin resonance spectrum of a free radical or coordination complex with one unpaired electron is the simplest of all forms of spectroscopy. The degeneracy of the electron spin states characterized by the quantum number, ms = 1/2, is lifted by the application of a magnetic field, and transitions between the spin levels are induced by radiation of the appropriate frequency (Figure 1.1). If unpaired electrons in radicals were indistinguishable from free electrons, the only information content of an ESR spectrum would be the integrated intensity, proportional to the radical concentration. Fortunately, an unpaired electron interacts with its environment, and the details of ESR spectra depend on the nature of those interactions. The arrow in Figure 1.1 shows the transitions induced by 0.315 cm-1 radiation. 

D.J.E. Ingram, Free Radicals as Studied by Electron Spin Resonance, Butterworth, London, 1958. 

P.F. Knowles, J.F. Gibson, F.M. Pick, and R.C. Bray, Electron-spin-resonance evidence for enzymic reduction of oxygen to a free radical, the superoxide ion. Biochem. J. Ill, 53-58 (1969). 

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