Radicals in Biological Systems

1 Radicals in Biological Systems. - The ability to resolve two separate lines with g factors gi and g2 depends on the inhomogeneous linewidth AB1/2 (which is often dominated by unresolved hyperfine interactions in biological systems) and is governed by the relationship 

A further study on the same system at 130 GHz but this time on fully deuterated Photosystem II samples from Synechococcus lividus produced a better resolved spectrum with a much higher signal to noise ratio. This gave further proof that both sets of radicals were produced at all temperatures but with the chlorophyll produced predominantly at the higher temperatures. Measured principal g values of the P-carotenoid were found to be gxx = 2.00335, gyy = 2.00251, gzz = 2.00227 and those for the chlorophyll z were gxx = 2.00312, gyy = 2.00263, gzz = 2.00202, similar to those of the chlorophyll a radical-cation. 

The role of histones in DNA in chromatin has been examined in a multifrequency study at 10 GHz and 285 GHz. The measurement of X-irradiated dry chromatin at 77 K and 285 GHz helped to confirm earlier studies that the characteristic spectra are produced from contributions of the DNA-based rad- 

The tyrosyl radical was also identified in a study of radical intermediates in turnip peroxidase isozymes. Reaction of turnip isoperoxidases 1, 3 and 7 with hydrogen peroxide causes the formation of an exchange-coupled oxoferryl-porphyrinyl radical species but, unexpectedly, at basic pH it was shown from high-field measurements that a hydrogen-bonded tyrosyl radical (gx = 2.0066) 

High-field studies have also been performed on a number of radicals in ID orientated membrane fragments to determine the orientation of the radical with respect to the membrane with measurements made on the stable tyrosyl radical Yd, the pheophytin anion and semiquinone Strong orientation and 

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Volume 105. Oxygen Radicals in Biological Systems Edited by Lester Packer... 

Pou, S., Hassett, D.J., Britigan, B.E., Cohen, M.S., and Rosen, G.M. 1989. Problems associated with spin trapping oxygen-centered free radicals in biological systems. Analytical Biochemistry 177 1-6. 

The continuous development of phenoxyl radical complexes started with an aim of modeling primarily the enzyme GO. The number of papers cited testily to the uninterrupted interest in this chemistry. Thus a small selection of more recent references from the literature including reviews (224), theoretical (225) and model studies (226), and characterization of tyrosyl radicals in biological systems (227) will close this chapter. 

On Geometrical and Spatial Factors Governing the Behavior OE Ion-Radicals in Biological Systems... 

Miyazawa T, Fujimoto K, Suzuki T, Yasuda K. Determination of phospholipid hydroperoxides using luminol chemiluminescence high-performance liquid chromatography. Oxygen Radicals in Biological Systems, Pt. C 233, 324-332, 1994. 

W. Jessup, R. T. Dean and J. M. Gebicki, in Oxygen Radicals in Biological Systems, Part C (Ed. L. Packer), Academic Press, San Diego, Methods EnzymoL, 233, 289 (1994). 

Guanine is the most easily oxidizable natural nucleic acid base [8] and many oxidants can selectively oxidize guanine in DNA [95]. Here, we focus on the site-selective oxidation of guanine by the carbonate radical anion, COs , one of the important emerging free radicals in biological systems [96]. The mechanism of COs generation in vivo can involve one-electron oxidation of HCOs at the active site of copper-zinc superoxide dismutase [97, 98], and homolysis of the nitrosoperoxycarbonate anion (0N00C02 ) formed by the reaction of peroxynitrite with carbon dioxide [99-102]. 

Garrel, C. Fontecave, M. Nitric oxide chemistry and biology, Analysis of Free Radicals in Biological Systems Eds. Favier, A. E. Cadet, J. Kalyanaraman, B. Fontecave, M. Pierre, J.-L. Birkhauser Verlag Basel, 1995, pp. 21-35. 

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