Hydroperoxides structural characterization

Teeth whiteners, percarbamide, 623 Temperature, reaction rates, 903-12 Terminal olefins, selenide-catalyzed epoxidation, 384-5 a-Terpinene, peroxide synthesis, 706 a-Terpineol, preparation, 790 Terrorists, dialkyl peroxide explosives, 708 Tertiary amines, dioxirane oxidation, 1152 Tertiary hydroperoxides, structural characterization, 690-1... 

Another derivatization approach is reduction of the hydroperoxide, followed by structural characterization of the corresponding alcohol, which is usually easier to handle. Thus, the structure of amino acid hydroperoxides can be characterized more easily if, after having ascertained the hydroperoxide nature of the compound, it is reduced to the alcohol with NaBH4. The structure of three valine hydroperoxides obtained on y-radiation of bovine serum albumin, a tripeptide (31) or valine (34) was elucidated after reduction, hydrolysis (if necessary), chromatographic separation, and application of the usual MS and NMR methods on the individual hydroxy derivatives of valine. ... 

Relatedly, despite the synthesis and structural characterization of numerous arsine and stibine oxides, bomb calorimetry measurements have only been reported on triphenylarsine oxide . While corresponding measurements have been made on triphenylarsine, it is clearly premature to make general observations as to E—O bond enthalpies in the absence of additional data. In principle, reaction calorimetry should prove useful. Indeed, we note a solution phase (benzene) enthalpy of reaction study of triphenylarsine and -butyl hydroperoxide according to the reaction... 

Although LOX from soybean seed is the best characterized of plant LOXs, this enzyme is present in a wide variety of plant and animal tissues (Liavonchanka and Feussner, 2006). The enzyme occurs in a variety of isoenzymes, which often vary in their optimum pH and in product and substrate specificity. Given the occurrence of multiple LOX isoenzymes in soybean leaves and the proposed roles of these enzymes in the plant metabolism, it is possible that individual isoenzymes play specific functions (Feussner and Wasternack 2002). The molecular structure of soybean LOX is the most reported, and four isoenzymes have been isolated (Baysal and Demirdoven 2007). Soy isoenzyme 1 produces 9- and 13-hydroperoxides (1 9) when the enzyme acts on free PUFA at pH 9.0, its optimum pH (Lopez-Nicolas and others 1999). Soy isoenzyme 2 acts on triglycerides as well as free PUFA leading to 9- and 13-hydroperoxide... 

An almost complete description of both OH radical-mediated and one-electron oxidation reactions of the thymine moiety (3) of DNA and related model compounds is now possible on the basis of detailed studies of the final oxidation products and their radical precursors. Relevant information on the structure and redox properties of transient pyrimidine radicals is available from pulse radiolysis measurements that in most cases have involved the use of the redox titration technique. It may be noted that most of the rate constants implicating the formation and the fate of the latter radicals have been also assessed. This has been completed by the isolation and characterization of the main thymine and thymidine hydroperoxides that arise from the fate of the pyrimidine radicals in aerated aqueous solutions. Information is also available on the formation of thymine hydroperoxides as the result of initial addition of radiation-induced reductive species including H" atom and solvated electron. 

Lesniak J, Barton WA, Nikolov DB (2002) Structural and functional characterization of the Pseudomonas hydroperoxide resistance protein Ohr. EMBO J 21 6649-6659 Lesniak J, Barton WA, Nikolov DB (2003) Structural and functional features of the Escherichia coli hydroperoxide resistance protein OsmC. Protein Sci 12 2838-2843 Lill R, Kispal G (2000) Maturation of cellular Fe-S proteins an essential function of mitochondria. Trends Biochem Sci 25 352-356 Lill R, Miihlenhoff U (2005) Iron-sulfur protein biogenesis in eukaryotes. Trends Biochem Sci 30 133-141... 

BASIC PROTOCOL 2 HPLC ANALYSIS OF REGIO- AND STEREOCONFIGURATION OF PRODUCTS In order to thoroughly characterize the LOX of interest, an optional procedure is offered to determine the regio- and stereospecificity of oxidation. For this purpose a reaction volume is used that is somewhat larger than that described in Basic Protocol 1 and the Alternate Protocol. The product hydroperoxides are reduced to their corresponding hydroxides, purified by TLC, methyl esterified, and separated by straight-phase HPLC followed by chiral-phase HPLC. In this way a complete structural analysis is obtained. 

Another polymer which is easily peroxidized is polyacetaldehyde it has a polyacetalic structure and is characterized by the presence of some side hydroperoxide groups (1 to 4°/00) due to traces of peracetic acid when the polymer is prepared. The homolytic decomposition of these peroxide groups yields macroradicals to which methyl methacrylate could be grafted [73, 74). 

Knowledge about the chemical structure of the antioxidative MRP is very limited. Only a few attempts have been made to characterize them. Evans, et al. (12) demonstrated that pure reductones produced by the reaction between hexoses and secondary amines were effective in inhibiting oxidation of vegetable oils. The importance of reductones formed from amino acids and reducing sugars is, however, still obscure. Eichner (6) suggested that reductone-like compounds, 1,2-enaminols, formed from Amadori rearrangement products could be responsible for the antioxidative effect of MRP. The mechanism was claimed to involve inactivation of lipid hydroperoxides. 

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