Free radical proteins

DIrIgent protein Free radical capture and stereoselective coupling... 

Brownson, C. and Hipkiss, A. R. (2000). Camosine reacts with a glycated protein. Free Radic. Biol. Med. 28,1564-1570. 

Siraki, A.G., Deterding, L.J., Bonini, M.G., Jian, J., Ehrenshaft, M., Tomer, K.B. and Mason, R.P. (2008) Procainamide, but not N-Acetylprocainamide, induces protein free radical formation on myeloperoxidase a potential mechanism of agranulocytosis. Chemical Research in Toxicology, 21, 1143-1153. 

The free radical X could be a protein free radical or a porphyrin n-cation radical... 

Methods for detecting ferryl iron and protein free radicals 4.1. X-ray crystallography... 

With ferryl myoglobin, in contrast to peroxidases, the reactions of the protein free radicals and that of the ferryl haem can be considered as uncoupled from each other. The protein has not been designed to form a cation radical for a specific reaction therefore not only is more than one cation free radical generated, but there is no control over their subsequent reactions. A similar situation can be observed in cytochrome c peroxidase mutants that have lost tryptophan-191. A different amino-acid free radical is still formed that is less stable. Indeed, even in the presence of tryptophan-191, small amounts of other free radicals are formed [237] this is further evidence that even in enzymes it is difficult to exclusively control free radical reactions. 

Ferryl myoglobin species (either the FeIV=0 itself or the protein free radicals) are capable of catalysing lipid peroxidation in model membranes [238], erythrocytes [239] and low-density lipoproteins [240]. They can also oxidise phenols, styrene, 3-carotene and ascorbate [211], At high peroxide levels, protein cross-linking is observed, followed by iron release which can result in Fenton chemistry in vitro. However, it is difficult to see how the peroxide haem ratio can ever be high enough in vivo to initiate these reactions. 

In spite of the protective effect of several antioxidant enzymes and metal-binding proteins, free radicals are still widely prevalent. Thus, Ames et al. (A 10) estimated that in each rat cell there are 100,000 radical hits each day, while in every human cells there are 10,000/day. Importantly, there are numerous natural free radical scavengers/chain breakers, the most notable being vitamins C andE, various carotenoids (beta-carotene, lycopene, etc.), flavonoids (rutin, quercetin, catechin, etc.), uric acid, and bilirubin, among others (Table 2). 

A20. Ayala, A., and Cutler, R. G., The utilization of 5-hydroxyl-2-amino valeric acid as a specific marker of oxidised arginine and proline residues in proteins. Free Radicals Biol. Med. 21,65-80 (1996). 

D10. Dean, R. T., Hunt, J. V., Grant, A. J., Yamamoto, Y., and Niki, E., Free radical damage to proteins The influence of file relative localization of radical generation, antioxidants, and target proteins. Free Radicals Biol. Med. 11, 161—168 (1991). 

Soszynski, M., and Bartosz, G., Decrease in accessible thiols as an index of oxidative damage to membrane proteins. Free Radicals Biol. Med. 23, 463-469 (1997). 

Wl. Waeg, G., Dimsity, G., and Esterbauer, H., Monoclonal antibodies for detection of 4-hydroxynonenal modified proteins. Free Radicals Res. 25, 149—159 (1996). 

A serious problem arises when lipids undergo peroxidation in the presence of protein. Free radicals originating from hydroperoxides transfer to several specific amino acid residues of protein. As a result, the protein undergoes radical induced polymerization, with loss of solubility and other original properties including nutritive value. 

Hunt JV, Wolff SP. The role of histidine residues in the nonenzymic covalent attachement of glucose and ascorbic acid to protein. Free Radical Res Commun 1991 14 279-287. 

Kirkwood, T. B. and Kowald, A. A network theory of ageing the interactions of defective mitochondria, aberrant proteins, free radicals and scavengers in the ageing process. Mutation Research 316 209-236 1996. 

Brand MD, Affourtit C, Esteves TC, Green K, Lambert AJ, Miwa S, Pakay JL, Parker N (2004) Mitochondrial superoxide production, biological effects, and activatiim of uncoupling proteins. Free Radic Biol Med 37 755—767... 

Free peroxyl radicals react with proteins with the formation of protein free radicals, which react with other protein free radicals to yield protein dimers, or with lipid free radicals to yield copolymers. The occurrence of a lipoprotein with covalent bonds and protein oligomers during oxidation of proteins (PH) by alkoxyl (RO ) and peroxyl (ROO ) radicals is shown in the following equations. A protein radical (P ) forms most frequently by splitting off the labile hydrogen atom on C , an alkoxyl radical yields a hydroxy acid and a peroxyl radical yields hydroperoxide ... 

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