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排序方式: 共有232条查询结果,搜索用时 15 毫秒
61.
Alexander G. Zhdanko 《Tetrahedron》2009,65(24):4692-2000
Fully protected natural and unnatural N-acetylcysteine, dipeptide Cys-Gly, glutathione, and homoglutathione derivatives were synthesized by the Ugi four-component reaction using various benzylthio aldehydes and ketones as carbonyl building blocks. The scope and limitations of the method were investigated. Formation of imidazoline by-products in the Ugi reaction was discussed. 2,2,2-Trifluoroethanol was shown to be a superior reaction media than methanol in some reactions. Also, the 4-methyl-2,6,7-trioxabicyclo[2.2.2]octyl derivative (OBO-ester) of isocyanoacetic acid was shown to be superior to use than ethyl isocyanoacetate as a peptide synthesis precursor in cases when higher reactivity of an isocyanide is required. 相似文献
62.
Gcineka Mbambisa 《Microchemical Journal》2009,93(1):60-66
Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10− 7 to 10− 6 M. 相似文献
63.
64.
Héctor Rosas Leidy Erika Sarmiento Vito Lubes María Goncalves Mary Lorena Araujo Felipe Brito 《Journal of solution chemistry》2008,37(5):701-711
The complex species formed between vanadium(III) cysteine and small blood serum bioligands: lactic, oxalic, citric and phosphoric
acids were studied in aqueous solution by means of electromotive force measurements, Emf(H), at 25 °C and 3.0 mol⋅dm−3 KCl as the ionic medium. The ternary complexes were studied by potentiometric measurements and the data analyzed using the
least-squares computational program LETAGROP to obtain the respective stability constants and stoichiometric coefficients.
The UV-Vis spectrophotometric measurements were done in order to make a qualitative characterization of the complexes formed
in aqueous solution. 相似文献
65.
Masahiko ABE Robert S. SCHECHTER Robert D. SELLIAH Baharuddin SHEIKH William H. WADE 《Journal of Dispersion Science and Technology》2013,34(2):157-172
This paper describes the effect of pH on phase behavior of branched tail EO carboxylate surfactants in electrolyte/ alkane microemulsion system3 which are of possible pertinence to enhanced oil recovery. The pH of the aqueous surfactant solutions was found to have a considerable effect on the salinity requirement for middle phase microemulsion formation. At 70 and 60°C alcohol-free optimal three phase microemulsion systems are formed with all alkanes studied over the entire pH range of 6-12. At lower temperatures and. higher pH values, liquid crystals were found to form in systems which contained lower molecular weight alkanes. 相似文献
66.
In the present study, a novel mixture consisting of N,N′‐bis(salicylidene)‐1,2‐phenylenediamino cobalt (CoSalophen, CoSal) complex and (n‐butyl)4SiW12O40 (SiW12), have been used to chemically modify a carbon paste electrode (CPE) for sensitive determination of cysteine (CySH). The electrocatalytic effect of the newly developed modified CPE towards oxidation of CySH was evaluated by comparing cyclic and differential pulse voltammograms in the presence of cysteine at bare, CoSal, SiW12 and CoSal/SiW12 modified CPE. The differential pulse voltammetry method was applied as a sensitive method for quantitative detection of CySH trace amounts, the experimental conditions being optimized in order to evaluate the best analytical parameters of the sensor. Reproducibility and stability studies were also performed and the sensor was applied for the determination of CySH in a pharmaceutical sample and in human blood serum and urine samples. 相似文献
67.
Jaime De Andres-llopis Antonio Aguilar-navarro Jorge Domenech 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1575-1585
Abstract The reaction kinetics of atactic polypropylene (APP) in bulk with dicumyl peroxide (DCP) as a radical generator have been studied by means of thermal differential analysis. Hydrogen abstraction from APP by cumyl radicals gives (polypropylen)yl radicals which undergo transfer to DCP, chain scission, disproportionation, and crosslinking, as well as reaction with cumyl radicals. Chain scission is shown to be the faster and crosslinking the slower of these two processes, even at temperatures of 473 K and above. Activation parameters are determined, and an analysis of the different processes is made on their basis. 相似文献
68.
Sheng Chen Jianniao TianYixuan Jiang Yanchun ZhaoJuanni Zhang Shulin Zhao 《Analytica chimica acta》2013
In this paper, we report a simple, selective, sensitive and low-cost turn-on photoluminescent sensor for cysteine and homocysteine based on the fluorescence recovery of the CdTe/CdS quantum dots (QDs)–phenanthroline (Phen) system. In the presence of Phen, the fluorescence of QDs could be quenched effectively due to the formation of the non-fluorescent complexes between water-soluble thioglycolic acid (TGA)-capped QDs and Phen. Subsequently, upon addition of cysteine and homocysteine, the strong affinity of cysteine and homocysteine to QDs enables Phen to be dissociated from the surface of QDs and to form stable and luminescent complexes with cysteine and homocysteine in solution. Thus, the fluorescence of CdTe/CdS QDs was recovered gradually. A good linear relationship was obtained from 1.0 to 70.0 μM for cysteine and from 1.0 to 90.0 μM for homocysteine, respectively. The detection limits of cysteine and homocysteine were 0.78 and 0.67 μM, respectively. In addition, the method exhibited a high selectivity for cysteine and homocysteine over the other substances, such as amino acids, thiols, proteins, carbohydrates, etc. More importantly, the sensing system can not only achieve quantitative detection of cysteine and homocysteine but also could be applied in semiquantitative cysteine and homocysteine determination by digital visualization. Therefore, as a proof-of-concept, the proposed method has potential application for the selective detection of cysteine and homocysteine in biological fluids. 相似文献
69.
Hao-Ran Qu Zi-You Zhang Nan Wang Qian Sun Shan-Shan Liu Wei-Bing Zhang Jun-Hong Qian 《中国化学快报》2015,26(10):1249-1254
The synthesis of three isomers based on Michael addition mechanism for the detection of sulfurcontaining species in aqueous solution is described. These compounds are constructed by conjugating an enone to a coumarin fluorophore. A substituted-phenyl (o, m, or p-) was appended at the carbonyl carbon to adjust the reactivity. The experimental results showed that (E)-7-(diethylamino)-3-(3-(3-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (m-QPS) and (E)-7-(diethylamino)-3-(3-(4-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (p-QPS) barely react with sulfur-containing nucleophiles, while (E)-7-(diethylamino)-3-(3-(2-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (o-QPS) exhibited a fast response toward sulfite, sulfide and thiols in DMSO/phosphate buffer (2:1). The above results are probably due to the intramolecular H-bonding activated Michael addition. More interestingly, cysteine triggered unusual photophysical responses of o-QPS:the original absorption (488 nm) and emission peaks (573 nm) underwent significant blue shifts initially and then recovered, which might be caused by the Michael addition and elimination reaction, respectively. 相似文献
70.
Determination of Cysteine at Bismuth Nanostructure – Carbon Ionic Liquid Electrode by Square Wave Voltammetry 下载免费PDF全文
Bismuth nanostructure‐carbon ionic liquid electrode has been employed for sensitive determination of cysteine (Cys). Bismuth nanostructure was incorporated into the carbon ionic liquid electrode (CILE) and applied for determination of cysteine. An interaction was taking place between bismuth nanostructure and the thiol group of cysteine. The bismuth cysteinate complex oxidation potential occurred at more negative potential compared to the cysteine oxidation peak obtained at bare carbon ionic liquid electrode (CILE). Square wave voltammetry (SWV) was used for the determination of the cysteine and satisfactory results were obtained. The calibration curve was linear in the concentration range of 1 to 500 µM and 0.5–2 mM of Cys. A low detection limit of 0.5 µM was achieved for Cys. The electrode showed a good selectivity for determination of cysteine in the presence of other amino acids. The proposed electrode was satisfactory applied for the determination of cysteine in human serum plasma sample. 相似文献