Liquid chromatographic determination of sulindac and metabolites in serum

An improved liquid chromatographic procedure is described for the quantitative determination of sulindac, sulindac sulfone, and sulindac sulfide from serum. The procedure makes use of acetonitrile extraction of the compounds of interest from acidified serum samples. Under these conditions extraction efficiencies in the 85 percent range are obtained for each of the compounds. The liquid chromatographic separation of the compounds of interest and the internal standard (indomethacin) is accomplished in an isocratic elution procedure using a nitrile (CN) stationary phase. The HPLC separation procedure is completed in less than 10 minutes, giving excellent resolution and peak shape.     

Sample preparation for the determination of steroids (corticoids and anabolics) in feed using LC

An improved sample preparation procedure for the determination of 17 steroids (corticoids (CC) and androgenic anabolic steroids (AAS)), used potentially as growth promoters, in feed samples has been developed. This procedure is based on two reported LC-UV methods. The improved procedure includes a leaching process using ACN, saponification, and SPE using polymeric cartridges. The proposed method was validated according to the EU criteria established for quantitative screening methods in PFS. The extraction efficiencies, decision limits (CCalpha) and detection capabilities (CCbeta), for these compounds were in the ranges of 82-100%, 19-40, and 24-53 microg/kg, respectively. The repeatability and the within-laboratory reproducibility at 1.0, 1.5, and 2.0 CCbeta levels were smaller than 10%. Accuracy was in the 97-101% range. The robustness was evaluated using the Youden robustness test. This method was applied to the analysis of steroids in different kinds of FS with satisfactory results.     

Direct synthesis of 4-arylpiperidines via palladium/copper(I)-cocatalyzed Negishi coupling of a 4-piperidylzinc iodide with aromatic halides and triflates

A general procedure for the synthesis of 4-arylpiperidines via the coupling of 4-(N-BOC-piperidyl)zinc iodide with aryl halides and triflates is presented. The reaction requires cocatalysis with both Cl(2)Pd(dppf) and a copper(I) species. An improved, safer procedure for the activation of zinc dust is also presented.     

Determination of dietary fibre as non-starch polysaccharides by gas-liquid chromatography.

An improved method is described for the measurement of total, soluble and insoluble dietary fibre as non-starch polysaccharides (NSP). An established procedure is modified to allow more rapid removal of starch and hydrolysis of NSP. In its present form the procedure is simpler and more robust than those previously published. In the modified method starch is removed enzymically within 50 min and NSP is precipitated with ethanol and then hydrolysed by treatment with sulfuric acid for 2 h. The constituent sugars can in turn be measured by gas-liquid chromatography, high-performance liquid chromatography or more rapidly by colorimetry. The improved procedure described here for the removal of starch and hydrolysis of NSP applies to all three techniques, but only the method for measurement of sugars by gas-liquid chromatography is described here in full.     

Improved density functional theory/electrostatic calculation of the His291 protonation state in cytochrome C oxidase: self-consistent charges for solvation energy calculation

The protonation state of His291 in cytochrome c oxidase (CcO), a ligand to the Cu(B) center of the enzyme, has been recently studied in this group by using combined density functional theory (DFT)/electrostatic (QM/MM) calculations. On the basis of these calculations, a model of the proton pumping mechanism of CcO has been proposed. Due to certain technical difficulties, the procedure used in the previous calculation to find partial atomic charges of the QM system for the solvation energy evaluation was not entirely satisfactory; i.e., it was not self-consistent. Here, we describe a procedure that resolves the problem and report on the improved calculations of the protonation state of the His residue. The new procedure fits the protein and reaction field potentials in the region of the QM system with artificial point charges placed on a surface of a sphere surrounding the QM system and a few charges inside the sphere and allows one to perform DFT calculations that involve an inhomogeneous dielectric environment in a self-consistent way. The procedure improves the accuracy of calculations in comparison with previous work. The improved results show, however, that although the absolute energies change significantly the relative energies of the protonated and deprotonated states of His291 remain close to the previously reported ones and therefore do not change significantly the pK(a) values reported earlier. Therefore, our new improved calculations support for the proposed His291 model of the CcO pump.     

A novel droplet-tap sample-loading method for two-dimensional gel electrophoresis

A novel procedure, droplet-tap mode, has been devised for sample application for two-dimensional gel electrophoresis (2DE) expression profiles. The sample was loaded by evenly distributed tapping of droplets of the sample on to the rehydration buffer (RB) and then lowering the strip on to the solution surface. At normal loading concentrations, the number of spots obtained was increased by approximately one-third by this new approach compared with the rehydration loading procedure. The method also resulted in significantly improved resolution compared with cup loading when high concentrations of proteins were present, indicating its potential usefulness in micropreparative separation. In addition, recovery of the proteins confirmed that protein uptake was enhanced by use of this method. By enabling improved performances in 2DE, the proposed procedure has much potential for sample loading to meet the requirements of global proteome analysis.Electronic Supplementary Material Electronic Supplementary Material found in     

改进的方法用于制备键合型纤维素－三（苯基氨基甲酸酯）手性固定相

The classical method for preparation of covalently boned cellulose derivative chiral stationary phases (CSP) with diisocyanate as spacer was improved. Diisocyanate was firstly allowed to react with 3-aminopropyltriethoxysilane, and the resulting product was then applied as the spacer reagent to immobilize cellulose derivatives onto silica gel. Influences of the amount and the length of the spacer on the optical resolution ability of the CSP were investigated. Comparing improved procedure to classical diisocyanate method, the cross-linking between the glucose units of the cellulose derivatives was avoided to the most extent. With the improved procedure, regio-nonselective ways could be adooted to prepare covalently bonded CSP, which showed an advantage for the rapid preparation.     

Volumetric method for the determination of uranium in the active process solutions

The DAVIES and GRAY method for the determination of uranium has been scaled down to facilitate the analysis of the radioactive solutions encountered in the fuel reprocessing plants. The sensitivity of the end point detection is improved by carrying out suitable modification in the procedure. Two procedures are described: (1) 70-ml procedure for the determination of 5–25 mg uranium, and (2) 30-ml procedure for 1–5 mg of uranium. The coefficient of variation is about 0.2% for 2–25 mg of uranium.     

Determination of oxygen in bismuthate single crystals

An improved procedure for determining oxygen in single crystals was developed. The procedure was tested on samples prepared from stoichiometric BaBiO₃ by thermal treatment in a controlled medium. The error of the procedure is about 0.5 mol%.     

A Facile,Sequential Multicomponent Approach to N-Aminoamidinothioureas—Versatile Synthons to Bioactive Heterocycles

A sequential, three-component approach for the rapid and convenient one-pot synthesis of N-aminoamidinothioureas is reported. The improved synthetic strategy involves the selective blocking of amino functionality in aminoguanidine by Schiff base formation with carbonyl compounds to generate corresponding N-(alkylidene/arylidene)aminoguanidines and their subsequent in situ condensation with isothiocyanate. The structural motif incorporates three points for diversity multiplication, making it a suitable candidate for combinatorial synthesis. The generality of the improved procedure was established by synthesizing a series of diverse compounds through solution phase parallel synthesis by varying the carbonyl and isothiocyanate components. The newly synthesized compounds were characterized by spectral methods. The developed synthetic procedure employs mild reaction conditions, and individual steps are carefully optimized for easy automation.     

Cobalt-catalyzed one-pot three-component coupling route to beta-acetamido carbonyl compounds: a general synthetic protocol for gamma-lactams

An efficient improved procedure for the synthesis of beta-acetamido carbonyl compounds is developed by a cobalt(II) chloride-catalyzed three-component coupling protocol. The procedure is also amenable to the synthesis of gamma-lactams by a three-component coupling reaction with use of 2-carbomethoxybenzaldehyde. The beta-acetamido carbonyl compounds derived from 2-carbomethoxybenzaldehyde are useful intermediates as they can be transformed to the corresponding gamma-lactams on treatment with base.     

The photometric determination of cobalt by extraction with b -nitroso-a-naphthol

An improved procedure has been described for the photometric determination of cobalt by extraction of the β-mtroso-α-naphthol complex with chloroform. This procedure can be applied in the presence of large amounts of foreign elements. Interfering elements are: gold, palladium, platinum and copper (above 25 mg).The method has been applied to the determination of cobalt in steels, non-ferrous alloys and nickel.     

Phosphonate-free phosphorylation of alcohols using bis-(tert-butyl) phosphoramidite with imidazole·hydrochloride and imidazole as the activator

A variety of commercially available alcohols were converted to their bis-(tert-butyl) protected mono-phosphate pro-drugs. The improved procedure uses the unique combination of imidazole·hydrochloride and imidazole as the activator to suppress the formation of undesired phosphonate by-product frequently encountered with the bis-(tert-butyl) phosphoramidite reagents. The new activation procedure eliminates the need to use excess reagents.     

3-(2-Arylhydrazono)-1,1,1-trifluro-3-(phenylsulfonyl)propan-2-ones as selective carboxylesterase inhibitors

Russian Chemical Bulletin - We improved the synthetic procedure for 3-(2-arylhydrazono)-1,1,1-trifluro-3-(phenylsulfonyl)propan-2-ones and established their structure. The study of their esterase...     

A universal screening assay for glycosynthases: directed evolution of glycosynthase XynB2(E335G) suggests a general path to enhance activity

Glycosynthases are catalytic mutants of mainly retaining glycoside hydrolases that catalyze the synthesis of oligosaccharides from their corresponding glycosyl-fluoride donors and suitable acceptors. Here we describe the development of a general, high-throughput screening procedure for glycosynthase activity, which is based on the release of hydrofluoric acid, a by-product of all glycosynthase reactions. This assay is sensitive, does not require the synthesis of special chromophoric or modified substrates, and, most importantly, is applicable for all glycosynthases. We used this screening procedure on error-prone PCR libraries to isolate improved glycosynthase variants of XynB2(E335G) glycosynthase, a family 52 beta-xylosidase from Geobacillus stearothermophilus. The improved variants exhibited higher K(M) values toward the acceptor and the donor, suggesting that enzyme-product release is rate determining for k(cat).     

电极法临床电解质分析仪进样流程的改进

针对目前临床电解质分析仪进样流程存在的问题，提出了新的进样流程，通过实际应用和计算机仿真表明，新的进样流程减少了流路液体残留的影响，提高了测量准确度。     

甲醛法测定铵盐中氮含量实验的改进

对铵盐中氮含量的测定(甲醛法)实验进行了改进,不仅减少了环境污染,降低了对操作者的影响,而且操作方便。改进后的方法已用于基础化学分析实验。     

Rongalite-promoted transition metal-free synthesis of S-aryl phosphorothioates

The improved procedure for the synthesis of S-aryl phosphorothioates from dialkyl phosphites (H-phosphonates), aryl iodides and elemental sulfur deals with the application of rongalite (sodium hydroxy-methanesulfinate) as the radical promoter. The reactions proceeded smoothly to give S-aryl phosphorothioates in good yields.     

Synthesis of hexahydropyridazine-3-phosphonic acid

The synthesis of hexahydropyridazine-3-phosphonic acid (piperidazine-3-phosphonic acid) was performed via a hetero-Diels-Alder reaction followed by Lewis acid-catalyzed phosphonylation. This two-step procedure was improved to a one-pot reaction.