排序方式: 共有35条查询结果,搜索用时 15 毫秒
1.
Klein E Nghiêm HO Valleix A Mioskowski C Lebeau L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(20):4649-4655
Thiamine (vitamin B1) is an essential nutritional factor metabolized inside the body in its mono-, di-, and triphosphate forms. Although the action of thiamine and thiamine diphosphate have been intensely investigated, many questions remain unanswered and the role of thiamine triphosphate is still especially unknown. To probe recent hypotheses on the implication of thiamine triphosphate in a new phosphorylation pathway involving synaptic proteins, we synthesized a series of thiamine di- and triphosphate analogues that are resistant to both enzymatic and chemical hydrolyses. The key step in the preparation of the title compounds is the coupling of thiamine propyl disulfide with adequately protected methylenebis-phosphonic acid, the corresponding triphosphate analogue, and difluoromethylenebisphosphonic acid. 相似文献
2.
The cyclic voltammetry of bismuth in aqueous media and electrochemical stripping determination of bismuth in aqueous and nonaqueous media after its extraction using a rotating disc electrode of glassy carbon was studied. To raise the conductivity of the organic medium and for the preparation of a convenients medium for the determination of bismuth, an alcoholic (methanol) solution of NH4SCN+HClO4 was employed. In non-aqueous medium bismuth can be determined down to concentrations 10?8M by anodic stripping voltammetry and to 5×10?8M by anodic stripping chronopotentiometry. The selectivity of the determination of bismuth after its extraction was studied. Electrochemical determination of 10?6M Bi3+ with error ±3–4% was not interfered with by these elements: Co2+, Ni2+, Zn2+, Cd2+, As3+ in the concentration 8×10?3M, Fe3+, In3+, Sn2+ and Sn4+ (5× 10?3M), Cu2+ (10?3M), Sb3+ (1.5×10?4M) and Hg2+ (2×10?5M). The reproducibility of the electrochemical determination of bismuth according to the recommended procedure is very good. 相似文献
3.
Nguyen Thanh Nghi 《Crystal Research and Technology》1985,20(10):1317-1323
The influence of the natural convection on the heat and mass transfer process during growth of GaP crystals from the solution is considered. The two-dimensional quasi-stationary thermodiffusive hydrodynamic problem for the GaP growth system by travelling solvent method (TSM), as a model, has been solved. Computation is given for the temperature and concentration field distribution in the solution. The picture of vortex configuration for different lengths of the liquid zone, the shape of the growing and dissolving interfaces and also the boundary layers thickness are obtained. The experimental dependence of the growth rate on the convection intensity observed mostly confirmed the calculation results. 相似文献
4.
R Bonfiglio RC King TV Olah K Merkle 《Rapid communications in mass spectrometry : RCM》1999,13(12):1175-1185
A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
5.
Background
Activation of fatty acids by acyl-CoA synthetase enzymes is required for de novo lipid synthesis, fatty acid catabolism, and remodeling of biological membranes. Human long-chain acyl-CoA synthetase member 6, ASCL6, is a form present in the plasma membrane of cells. Splicing events affecting the amino-terminus and alternative motifs near the ATP-binding site generate different isoforms of ACSL6. 相似文献6.
越南火龙果冷藏现状分析 总被引:1,自引:0,他引:1
随着全球化经济的快速发展,食品冷藏技术日益重要.文中综述了越南火龙果的现有冷藏技术及其存在的问题,并提出解决方案. 相似文献
7.
Hassan Osseili Khai‐Nghi Truong Thomas P. Spaniol Laurent Maron Ulli Englert Jun Okuda 《Angewandte Chemie (International ed. in English)》2019,58(6):1833-1837
Facile α‐H elimination from tetrakis(trimethylsilylmethyl)titanium precursors to give adducts of (alkylidene)bis(alkyl)titanium complexes is induced by light alkali metal amides of the NNNN‐type macrocyclic anionic ligand Me3TACD [(Me3TACD)H=1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane]. In the crystal, the alkali metal interacts with the carbene carbon atom or with the CH2 group of the trimethylsilymethyl ligand. The nucleophilic character of the carbene carbon atom was shown by the reaction with benzophenone and terminal acetylenes. 相似文献
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9.
Cyclic voltammetry of antimony was studied in aqueous media (HCl-LiCl) and in nonaqueous media after extraction with 20% tri-n-butylphosphate in toluene, with a rotating glassy carbon disc electrode. Reduction of antimony to the element in aqueous media is nearly reversible, but irreversible in nonaqueous media. Anodic stripping voltammetric and chronopotentiometric determinations were also studied in nonaqueous media; methanol and LiCI, NH4SCN or NH4NO3, were used as base electrolytes. In nonaqueous media, antimony can be determined down to concentrations of 1O−8 M by stripping voltammetry, and lO−7 M by stripping chronopotentiometry. Electrochemical stripping determinations of 10−6 M antimony(III) were not affected by Co2+, Ni2+, Cd2+, Zn2+ or As3+ (5 · 10−3 M), ag+ (4 · 10+4 M in stripping voltammetry or 10−3 M in stripping chronopotentiometry), Hg2+ (5 · 10−4M), Pb2+ (3 · 10−4 M), Cu2+ (1.5 · 10−4 M)Sn2+ and Sn4+ (7 · 10−4 M), Fe3+ (4 · 10−4 M), Au3+ (5 · 10−5 M) and Bi3+ (1.5 · 10−5 M). Thestripping chronopotentiometric determination showed better selectivity. 相似文献
10.
Tualle JM Nghiêm HL Schäfauer C Berthaud P Tinet E Ettori D Avrillier S 《Optics letters》2005,30(1):50-52
We present time-resolved measurements by speckle interferometry of the light scattered by a liquid medium. Measurements were performed by use of reflectance geometry and are compared with results obtained in the same conditions with a femtosecond laser and a streak camera. The setup was also tested in vivo on the forearm of a human volunteer to demonstrate the potential utility of such a setup for biomedical applications. 相似文献