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Oxidation Leads (oxidation + lead)
Selected AbstractsPE-UHMW in Hip Implants: Properties of Conventional and Crosslinked Prosthetic ComponentsADVANCED ENGINEERING MATERIALS, Issue 10 2009Ruth Markut-Kohl Hip implants made of crosslinked ultra high molecular weight polyethylene,PE-UHMW,(different as-received conditions) are compared with a retrieval made from non-crosslinked PE-UHMW and a control PE-UHMW. Oxidation leads to recrystallization and the enhanced crystallinity corresponds to higher hardness values. These structure-property relations are discussed for conventional PE-UHMW and also for crosslinked material. [source] Neutral and Oxidized Triisopropylsilyl End-Capped Oligothienoacenes: A Combined Electrochemical, Spectroscopic, and Theoretical StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2010Juan Aragó Abstract This work presents an analysis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end-capped oligothienoacenes (TIPS- Tn -TIPS, n=4,8) by combining cyclic voltammetry, spectroscopic techniques, and quantum-chemical calculations. TIPS- Tn -TIPS compounds form stable radical cations, and dications are only obtained for the longest oligomers (n=7 and 8). Oxidation leads to the quinoidization of the conjugated backbone, from which electrons are mainly extracted. The absorption and fluorescence spectra show partially resolved vibronic structures even at room temperature, due to the rigid molecular geometry. Two well-resolved vibronic progressions are observed at low temperatures due to the vibronic coupling, with normal modes showing wavenumbers of ,1525 and ,480,cm,1. Optical absorption bands display remarkable bathochromic dispersion with the oligomer length, indicative of the extent of , conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two intense absorption bands emerging at energies lower than in the neutral compounds. The formation of the dication is only detected for the heptamer and the octamer, and shows a new band at intermediate energies. Optical data are interpreted with the help of density functional theory calculations performed at the B3LYP/6-31G** level, both for the neutral and the oxidized compounds. [source] Increased temperature and protein oxidation lead to HSP72 mRNA and protein accumulation in the in vivo exercised rat heartEXPERIMENTAL PHYSIOLOGY, Issue 1 2009Jessica L. Staib Expression of myocardial heat shock protein 72 (HSP72), mediated by its transcription factor, heat shock factor 1 (HSF1), increases following exercise. However, the upstream stimuli governing exercise-induced HSF1 activation and subsequent Hsp72 gene expression in the whole animal remain unclear. Exercise-induced increases in body temperature may promote myocardial radical production, leading to protein oxidation. Conceivably, myocardial protein oxidation during exercise may serve as an important signal to promote nuclear HSF1 migration and activation of Hsp72 expression. Therefore, these experiments tested the hypothesis that prevention of exercise-induced increases in body temperature attenuates cardiac protein oxidation, diminishes HSF1 activation and decreases HSP72 expression in vivo. To test this hypothesis, in vivo exercise-induced changes in body temperature were manipulated by exercising male rats in either cold (4°C) or warm ambient conditions (22°C). Warm exercise increased both body temperature (+3°C) and myocardial protein oxidation, whereas these changes were attenuated by cold exercise. Interestingly, exercise in both conditions did not significantly increase myocardial nuclear localized phosphorylated HSF1. Nonetheless, warm exercise elevated left-ventricular HSP72 mRNA by ninefold and increased myocardial HSP72 protein levels by threefold compared with cold-exercised animals. Collectively, these data indicate that elevated body temperature and myocardial protein oxidation promoted exercise-induced cardiac HSP72 mRNA expression and protein accumulation following in vivo exercise. However, these results suggest that exercise-induced myocardial HSP72 protein accumulation is not a result of nuclear-localized, phosphorylated HSF1, indicating that other transcriptional or post-transcriptional regulatory mechanisms are involved in exercise-induced HSP72 expression. [source] A New Synthesis of Push-Pull Pyrroles, Their Oxidation to Stable 3H -Pyrroles and an Unexpected Anellation ReactionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2009Gunther Buehrdel Abstract A new synthesis of push-pull pyrroles of type 5 was developed starting from bis(imidoyl chlorides) 1 and various iminodiacetic acid derivatives 3. The use of appropriate N -trifluoroacetyl residues as protecting/activating group proved to be the method of choice for the straightforward preparation of the 3,4-diarylamino-1H -pyrroles 5. When benzothiazole substructures are present in 2,5-position of heterocycles 5, a two-electron oxidation leads to 3H -pyrroles of type 6 in excellent yields. However, in the case of cyano or ester groups, a further oxidative process immediately led to the new 3H -pyrrolo[3,4- b]quinoxalines 7 via intramolecular ring anellation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Reactivity of Tyr,Leu and Leu,Tyr dipeptides: identification of oxidation products by liquid chromatography,tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2009Conceição Fonseca Abstract The exposure of peptides and proteins to reactive hydroxyl radicals results in covalent modifications of amino acid side-chains and protein backbone. In this study we have investigated the oxidation the isomeric peptides tyrosine,leucine (YL) and leucine,tyrosine (LY), by the hydroxyl radical formed under Fenton reaction (Fe2+/H2O2). Through mass spectrometry (MS), high-performance liquid chromatography (HPLC-MS) and electrospray tandem mass spectrometry (HPLC-MSn) measurements, we have identified and characterized the oxidation products of these two dipeptides. This approach allowed observing and identifying a wide variety of oxidation products, including isomeric forms of the oxidized dipeptides. We detected oxidation products with 1, 2, 3 and 4 oxygen atoms for both peptides; however, oxidation products with 5 oxygen atoms were only present in LY. LY dipeptide oxidation leads to more isomers with 1 and 2 oxygen atoms than YL (3 vs 5 and 4 vs 5, respectively). Formation of the peroxy group occurred preferentially in the C -terminal residue. We have also detected oxidation products with double bonds or keto groups, dimers (YL,YL and LY,LY) and other products as a result of cross-linking. Both amino acids in the dipeptides were oxidized although the peptides showed different oxidation products. Also, amino acid residues have shown different oxidation products depending on the relative position on the dipeptide. Results suggest that amino acids in the C -terminal position are more prone to oxidation. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||