936 resultados para Radical


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This essay looks at the sedition trials in Scotland during the 1790s to examine how prosecution was exploited by radicals as a forum for political expression. As the government instituted a concerted campaign against radical activism, an increasing number of reformers faced trial on sedition and treason in this period. The courtroom emerged as an alternative venue for political discourse and this essay will explore some of the ways by which radicals challenged the dominant discursive and performative elements of trial proceedings. (c) 2005 Elsevier Ltd. All rights reserved.

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1. The ability of myo-inositol polyphosphates to inhibit iron-catalysed hydroxyl radical formation was studied in a hypoxanthine/xanthine oxidase system [Graf, Empson and Eaton (1987) J. Biol. Chem. 262, 11647-11650]. Fe3+ present in the assay reagents supported some radical formation, and a standard assay, with 5 microM Fe3+ added, was used to investigate the specificity of compounds which could inhibit radical generation. 2. InsP6 (phytic acid) was able to inhibit radical formation in this assay completely. In this respect it was similar to the effects of the high affinity Fe3+ chelator Desferral, and dissimilar to the effects of EDTA which, even at high concentrations, still allowed detectable radical formation to take place. 3. The six isomers of InsP5 were purified from an alkaline hydrolysate of InsP6 (four of them as two enantiomeric mixtures) and they were compared with InsP6 in this assay. Ins(1,2,3,4,6)P5 and D/L-Ins(1,2,3,4,5)P5 were similar to InsP6 in that they caused a complete inhibition of iron-catalysed radical formation at > 30 microM. Ins(1,3,4,5,6)P5 and D/L-Ins(1,2,4,5,6)P5, however, were markedly less potent than InsP6, and did not inhibit radical formation completely; even when Ins(1,3,4,5,6)P5 was added up to 600 microM, significant radical formation was still detected. Thus InsP5s lacking 2 or 1/3 phosphates are in this respect qualitatively different from InsP6 and the other InsP5s. 4. scyllo-Inositol hexakisphosphate was also tested, and although it caused a greater inhibition than Ins(1,3,4,5,6)P5, it too still allowed detectable free radical formation even at 600 microM. 5. We conclude that the 1,2,3 (equatorial-axial-equatorial) phosphate grouping in InsP6 has a conformation that uniquely provides a specific interaction with iron to inhibit totally its ability to catalyse hydroxyl radical formation; we suggest that a physiological function of InsP6 might be to act as a 'safe' binding site for iron during its transport through the cytosol or cellular organelles

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In the sera and synovial fluid of patients with rheumatoid arthritis, part of the IgG fraction is found in an aggregated and fluorescent form. Oxygen-free radicals have been implicated in this denaturation, although the precise radical species responsible is unknown. In this work, oxygen-free radicals generated radiolytically were allowed to attack polyclonal IgG in solution. OH radicals induced aggregation of the monomer and a new fluorescence appeared in the visible region (Ex 360 nm, Em 454 nm). The superoxide radical anion was found to be inert in both these respects, whilst peroxy radicals induced autofluorescence without concomitant aggregation. The results suggest that OH.and/or peroxy radical attack may be an in vivo mechanism for IgG denaturation.