Electron paramagnetic resonance signals

Electron-nuclear double resonance (ENDOR) spectroscopy A magnetic resonance spectroscopic technique for the determination of hyperfine interactions between electrons and nuclear spins. There are two principal techniques. In continuous-wave ENDOR the intensity of an electron paramagnetic resonance signal, partially saturated with microwave power, is measured as radio frequency is applied. In pulsed ENDOR the radio frequency is applied as pulses and the EPR signal is detected as a spin-echo. In each case an enhancement of the EPR signal is observed when the radiofrequency is in resonance with the coupled nuclei. 

F. Are the "g = 2.04" Electron Paramagnetic Resonance Signals Direct Observation of Nonheme Iron-Sulfur Nitrosylation ... 

Fig. 6. Electron paramagnetic resonance signal showing the g= 1.94 characteristic of the dithionite-reduced spinach ferredoxin, a plant-type iron-sulfur protein. Spectrum taken at 20 °K...

The observation of Mason and his colleagues of an electron paramagnetic resonance signal in microsomes, g=1.91, 2.25, 2.40, see Fig. 2, was made before it was known that this was a heme-iron signal (29). For a while the signal was also called Fef but this is now known to be P-450. The signals were later shown to be induced by those Fe substrates... 

Figure 3. Antioxidative effect and intensity of electron paramagnetic resonance signal for various fractions of Maillard reaction products from histidine and glucose.

This result is interesting but perhaps not very satisfying, since it puts an upper limit on the metal-anion distance without unequivocally revealing whether the anion is directly coordinated to the metal ion. To get at this question, we attached a nitroxyl spin-labeled anion to transferrin to determine whether its electron paramagnetic resonance signal was broadened by interaction with specifically bound Fe(III) (49). The mechanism of such broadening would be similar to that in the NMR experiments, but now there is an electron-electron interaction rather than an electron-nuclear interaction as before. 

Ioaninnidis, N. and Petrouleas, V. (2000) Electron paramagnetic resonance signals from S3 state of the oxygenOevolving complex. A broading radical signal induced by low temperature near-infrared light illumination, Biochemistry 39, 5246-5254. 

Bray, R. C., and VAnngArd, T., 1969, eRapidly appearing molybdenum electron paramagnetic resonance signals from reduced xanthine oxidase, Biochem. J. 114 725n734. 

Tris[bis(trimethylsilyl)amido] titanium(III) crystallizes from pentane as bright-blue needles, extremely sensitive to oxygen and moisture. Both the solid and hydrocarbon solutions of this compound give strong electron paramagnetic resonance signals at room temperature. The g -values obtained (go = 1.911 g t = 1.993 = 1.869) agree with values calculated from the ultraviolet/visible transi-... 

Our elucidation of the structure helps in the understanding of the ferromagnetism in this material. It was argued previously that TDAE-Cso is an itinerant ferromagnet that is, the unpaired spins are carried by delocalized electrons. We have measured the electron paramagnetic resonance signal in this material, and find a relatively low value for the g-factor, g = 2.0008. This implies that the open-shell species reside principally on the C. and to a lesser extent on the TDAE. 

GT Babcock and K Sauer (1975) A rapid, light-induced transient in electron paramagnetic resonance signal II activated upon inhibition of photosynthetic oxygen evolution. Biochim Biophys Acta 376 315-328... 

H Beinert, B Kok and G Hoch (1962) The light-induced electron paramagnetic resonance signal of photocatalyst P700. Biochem Biophys Res Commun 7 209-212... 

PA Loach, GM Androes, AF Maksim and M Caivin (1963) Variation in electron paramagnetic resonance signals of photosynthetic systems with the redox level of their environment. Photochem Photobiol 2 443-454 B Rumberg (1964) Analyse der Photosynthese mit Blitzlicht. II. Die Eigenschaften des Reaktionscyclus von Chlorophyll-a,-430-703. Z Naturforschung 19B 707-716... 

JS Rieske, WS Zaugg and RE Hansen (1964) Studies on the electron transfer system. LIX. Distribution of iron and of the component giving an electron paramagnetic resonance signal at g= 1.90 in subtractions of complex III. J Bioi Chem 239 3017-3022... 

For quantification of basal vascular nitric oxide ( NO) production from isolated vessels, Kleschyov et al. (2000) incubated rabbit aortic or venous strips with 250 (iM colloid Fe/diethyldithiocarbamate, which resulted in a linear increase in tissue-associated NO-Fe/diethyldithiocarbamate electron paramagnetic resonance signal during 1 h. Removal of endothelium or addition of 3 mM N -nitro-L-arginine methyl ester inhibited the signal. 

Incubation of rat embryonic mesencephalic tissue, rich in dopaminergic neurones, with 0.2 mM tert-butyl hydroperoxide in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide for 20 min resulted in the trapping of radicals (Karlsson et al. 2000). The main radicals detected in cell suspensions were the tert-butoxyl radical and the methyl radical, indicating the one-electron reduction of the peroxide followed by a P-scission reaction. The appearance of electron paramagnetic resonance signals from the trapped radicals preceded the onset of cytotoxicity, which was almost exclusively necrotic in nature. The inclusion of resveratrol (3,5,4 -trihydroxy-fra s-stilbene) in incubations resulted in the marked protection of cells from ferf-butyl hydroperoxide. 

Isolated rat hepatocytes exposed to IFN-y, TNF-a, IL-ip, and lipopolysaccharide demonstrated a g = 2.04 axial electron paramagnetic resonance signal... 

Polypyrrole was one of the earliest conducting polymers produced. In 1968 DalT-Olio et al. [2] oxidized pyrrole in aqueous sulfuric acid to obtain a powdery precipitate on a platinum electrode. Pyrrole black, as this material became known, had a conductivity of 8 S cm". Chemical analysis determined the presence of 75% poly pyrrole and 25% sulfate anions. An intense electron paramagnetic resonance signal indicated that the polymer possessed a large number of free spins and gave a g value of 2.0026 (comparable to that of a free electron, g = 2.0023). 

Maly T, MacMillan F, Zwicker K, Kashani-Poor N, Brandt U, Prisner TF. 2004. Relaxation filtered hyperfme (REFINE) spectroscopy a novel tool for studying overlapping biological electron paramagnetic resonance signals applied to mitochondrial complex I. Biochemistry 43 3969-3978. 

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