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71.
Characterization of dehydroascorbate‐mediated modification of glutaredoxin by mass spectrometry 下载免费PDF全文
Aurore Flandrin Sebastien Allouche Yoann Rolland François‐Olivier McDuff J. Richard Wagner Klaus Klarskov 《Journal of mass spectrometry : JMS》2015,50(12):1358-1366
Ascorbate is as a potent antioxidant in vivo protecting the organism against oxidative stress. In this process, ascorbate is oxidized in two steps to dehydroascorbate (DHA), which if not efficiently reduced back to ascorbate decomposes irreversibly to a complex mixture of products. We demonstrate that a component of this mixture specifically reacts with the thiol group of cysteine residues at physiological pH to give a protein adduct involving the addition of a 5‐carbon fragment of DHA (+112 Da). Incubations of glutaredoxin‐1 expressed in Escherichia coli and dehydroascorbate revealed abundant adducts of +112, +224 and +336 Da due to the addition of one, two and three conjugation products of DHA, respectively. ESI–MS of carbamidomethylated glutaredoxin‐1 before incubation with DHA, deuterium exchange together with tandem mass spectrometry analysis and LC–ESIMS/MS of modified peptides confirmed structure and sites of modification in the protein. Modification of protein thiols by a DHA‐derived product can be involved in oxidative stress‐mediated cellular toxicity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
72.
Divinyl‐End‐Functionalized Polyethylenes: Ready Access to a Range of Telechelic Polyethylenes through Thiol–Ene Reactions 下载免费PDF全文
Dr. Sebastien Norsic Dr. Coralie Thomas Dr. Franck D'Agosto Dr. Christophe Boisson 《Angewandte Chemie (International ed. in English)》2015,54(15):4631-4635
Telechelic α,ω‐iodo‐vinyl‐polyethylenes (Vin‐PE‐I) were obtained by catalytic ethylene polymerization in the presence of [(C5Me5)2NdCl2Li(OEt2)2] in combination with a functionalized chain‐transfer agent, namely, di(10‐undecenyl)magnesium, followed by treatment of the resulting di(vinylpolyethylenyl)magnesium compounds ((vinyl‐PE)2Mg) with I2. The iodo‐functionalized vinylpolyethylenes (Vin‐PE‐I) were transformed into unique divinyl‐functionalized polyethylenes (Vin‐PE‐Vin) by simple treatment with tBuOK in toluene at 95 °C. Thiol–ene reactions were then successfully performed on Vin‐PE‐Vin with functionalized thiols in the presence of AIBN. A range of homobifunctional telechelic polyethylenes were obtained on which a hydroxy, diol, carboxylic acid, amine, ammonium chloride, trimethoxysilyl, chloro, or fluoroalkyl group was installed quantitatively at each chain end. 相似文献
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Velve Casquillas G Fu C Le Berre M Cramer J Meance S Plecis A Baigl D Greffet JJ Chen Y Piel M Tran PT 《Lab on a chip》2011,11(3):484-489
One major advantage of using genetically tractable model organisms such as the fission yeast Schizosaccharomyces pombe is the ability to construct temperature-sensitive mutations in a gene. The resulting gene product or protein behaves as wildtype at permissive temperatures. At non-permissive or restrictive temperatures the protein becomes unstable and some or all of its functions are abrogated. The protein regains its function when returning to a permissive temperature. In principle, temperature-sensitive mutation enables precise temporal control of protein activity when coupled to a fast temperature controller. Current commercial temperature control devices do not have fast switching capability over a wide range of temperatures, making repeated temperature changes impossible or impractical at the cellular timescale of seconds or minutes. Microfabrication using soft-lithography is emerging as a powerful tool for cell biological research. We present here a simple disposable polydimethylsiloxane (PDMS) based microfluidic device capable of reversibly switching between 5 °C and 45 °C in less than 10 s. This device allows high-resolution live cell imaging with an oil immersion objective lens. We demonstrate the utility of this device for studying microtubule dynamics throughout the cell cycle. 相似文献
75.
Stöger B Weil M Baran EJ González-Baró AC Malo S Rueff JM Petit S Lepetit MB Raveau B Barrier N 《Dalton transactions (Cambridge, England : 2003)》2011,40(20):5538-5548
Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO(3)(H(2)O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 °C for 30 min. A temperature of 220 °C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO(3)(H(2)O) was determined from single crystal X-ray diffraction data: P2(1)/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5) ?, β = 107.210(1)°, V = 443.42(5) ?(3), 1403 structure factors, 63 parameters, R[F(2)>2σ(F(2))] = 0.0208, wR(F(2) all) = 0.0516, S = 1.031. SrTeO(3)(H(2)O) is isotypic with the homologous BaTeO(3)(H(2)O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO(6)(H(2)O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO(3)] units. The cohesion of the structure is accomplished by moderate O-H···O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO(3)(H(2)O) condensates above 150 °C to the metastable phase ε-SrTeO(3) and transforms upon further heating to δ-SrTeO(3). The crystal structure of ε-SrTeO(3), the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P2(1)/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2) ?, β = 126.4980(7)°, V = 341.20(18) ?(3), R(Fobs) = 0.0166, R(Bobs) = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of ε-SrTeO(3) shows the same basic set-up as SrTeO(3)(H(2)O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO(3)(H(2)O) and ε-SrTeO(3) are complemented by thermal analysis and vibrational spectroscopic measurements. 相似文献
76.
Zou X Zhang F Thomas S Zhu G Valtchev V Mintova S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(43):12076-12083
Continuous metal–organic framework‐type Co3(HCOO)6 intergrown films with a one‐dimensional zigzag channel system and pore aperture of 5.5 Å are prepared by secondary growth on preseeded macroporous glass‐frit disks and silicon wafers. The adsorption behavior of CO2 or CH4 single gases on the Co3(HCOO)6 membrane is investigated by in situ IR spectroscopy. It is shown that the isosteric heats of adsorption for CO2 (17.7 kJ mol?1) and CH4 (14.4 kJ mol?1) do not vary with increasing amount of adsorbed gases. The higher value of isosteric heat for CO2 is an indication of the stronger interaction between the CO2 and the Co3(HCOO)6 membrane. The Co3(HCOO)6 membrane is studied by binary gas permeation of CO2 and CH4 at different temperatures (0, 25, and 60 °C). The membrane has CO2/CH4 selectivity with a separation factor higher than 10, which is due to the unique structure and molecular sieving effect. Upon increasing the temperature from 0 to 60 °C, the preferred permeance of CO2 over CH4 is increased from 1.70×10?6 to 2.09×10?6 mol m?2 s?1 Pa?1, while the separation factor for CO2/CH4 shows a corresponding decrease from 15.95 to 10.37. The effective pore size of the Co3(HCOO)6 material combined with the pore shape do not allow the two molecules to pass simultaneously, and once the CO2 molecules are diffused in the micropores, the CH4 is blocked. The supported Co3(HCOO)6 membrane retains high mechanical stability after a number of thermal cycles. 相似文献
77.
Aim
The purpose of this study was to evaluate the intra- and interexaminer resegmentation precision of patellar cartilage T2 mapping measurements in healthy subjects.Materials and Methods
T2-weighted images of patellar cartilage for 10 subjects were acquired. Two individuals manually segmented patellar cartilage at each slice location twice, once on each of two separate days. Bulk average and zonal T2 values for the superficial, middle, and deep layers of cartilage were calculated. The root mean square (RMS) and coefficient of variation (COV) were calculated using the repeated measurements of each slice of each subject by each examiner.Results
The intraexaminer bulk T2 differences were 0.2±1.0 ms, with an RMS error of 0.7 ms and a COV of 1.9%. The differences of interexaminer bulk T2 values was 1.0±1.4 ms, with an RMS error of 1.2 ms and a COV of 3.3%. The superficial zone of cartilage had the highest zonal variability of T2 values. The average interexaminer T2 values for the superficial, middle and deep zones were 42.2±5.6, 38.1±5.3 and 31.9±4.6 ms, respectively.Conclusion
The interexaminer variability of calculated T2 values highlights the difficulty of interpreting significant differences of T2 values which are similar in magnitude. The repeatability measurements of patellar cartilage T2 values were less than reported intersession T2 repeatability. 相似文献78.
Zoltán Siklósy Attila Demény Torsten W. Vennemann Sebastien Pilet Jan Kramers Szabolcs Leél‐Őssy Mária Bondár Chuan‐Chou Shen Ernst Hegner 《Rapid communications in mass spectrometry : RCM》2009,23(6):801-808
Stable isotope analyses of speleothems (carbonate deposits formed in caves) have been widely used to reconstruct paleoenvironmental conditions. Recent improvements in geochemical techniques have enabled us to analyze climate‐influenced deposits at high temporal resolution so that hitherto unrecognized environmental conditions may be identified. Stable H, C and O isotope analyses on carbonate and inclusion water have been combined with multicollector inductively coupled plasma mass spectrometry (MC‐ICP‐MS) age dating and laser‐ablation ICP‐MS trace element analyses on a stalagmite from southern Hungary. The study reveals significant changes in chemical and isotopic compositions of the speleothem between approx. 3800 and 3500 years BP (‘Before Present’) indicating coupled changes in the temperature and precipitation regime under which the speleothem formed. Stable isotopic and trace element correlations within this time period correlate with similar studies of stalagmites of comparable age from the Alpine‐Mediterranean region. Our studies suggest that traces of deposition of volcanic dust, possibly related to the Thera eruption of Santorini (Greece) ca. 1650 BC (~3650 BP), and environmental changes can be detected at a distance of several thousand kilometers. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
79.
80.
Dr. Stephan N. Steinmann Dr. Carine Michel Dr. Renate Schwiedernoch Dr. Jean‐Sebastien Filhol Dr. Philippe Sautet 《Chemphyschem》2015,16(11):2307-2311
Our first principles simulations of the electrooxidation of formic acid over nickel identify the reorientation of the formate intermediate and the desorption of CO2 as the rate‐limiting steps. Although they are not associated with an electron transfer, these barriers are strongly modified when the electrochemical potential is explicitly accounted for and when modeling the influence of the solvent. Hence, such a level of modeling is key to understand the kinetic limitations that penalize the reaction. 相似文献