Efficient microwave combinatorial parallel and nonparallel synthesis of N-alkylated glycine methyl esters as peptide building blocks

An easy and convenient microwave-assisted synthesis of N-alkylated glycine methyl esters is described. Parallel and nonparallel combinatorial methods are described and compared. The described reactions are reductive alkylations of several aldehydes and glycine methyl ester in the presence of NaBH3CN. Good yields and short reaction times are the main aspects of these procedures.     

Hydrocolloid gels of polysaccharides and proteins

Recent developments from 1997 to 2000 in hydrocolloid gels which consist of dispersed phase (polysaccharide or protein) and dispersing medium (water) are reviewed in the present paper. Gels and gelling processes of polysaccharides such as gellan gum, methylcellulose, xyloglucan, curdlan, konjac glucomannan and starch are described. Fluid gels and galactomannan gels prepared by freeze-thaw cycling are also described. Effects of pH and ionic strength on the gelation of proteins such as casein and β-lactoglobulin are described. Fractal treatment is introduced to study the structure–property relationship for globular protein gels. Gels formed by different hydrocolloids are also described briefly.     

The variational alternant molecular orbital method for 3-D and 2-D hydrogen molecule

The Variational alternant molecular orbital method (VAMO ) is described and applied to the case of three-dimensional and two-dimensional hydrogen molecules. The energies of the electron system are obtained, together with the equilibrium distances of the molecules. The intergrals equivelent to the Slater's integrals of the nonvariational method are described. Applications of this method to realizable systems are described.     

Synthesis and mass spectra of 1-arylideneamino-1,2,3-triazoles

The synthesis of the title Compounds is described. Their mass spectra upon electron impact are given and the main fragmentation pathways are described.     

Calorimeters for biotechnology

The isothermal and temperature scanning calorimeters manufactured by Calorimetry Sciences Corporation are briefly described. Applications of calorimetry to determine thermodynamics and kinetics of reactions of interest in biotechnology are described with illustrative examples.     

低聚糖的固相合成与反应机理研究进展

对低聚糖的固相合成作了评述，重点介绍了聚合物载体对糖苷化反应的影响、羟基的保护（包括载体化保护基）、糖苷化反应的各种方法和偶联过程中的立体控制问题。     

Immobilized pH 2.5-11 gradients for two-dimensional electrophoresis.

Extremely wide immobilized pH gradients, pH 2.5-11, for isoelectric separation of complex protein mixtures are described. These pH gradients are theoretically and practically the maximum that can be achieved at present with the available acrylamido buffers and titrants. Conditions are described for reducing conductivity and electroendosmosis in extreme pH ranges. Furthermore, new conditions are described for the separation of proteins in the second dimension. Using this protocol, nearly all the possible cellular products can be separated in one single two-dimensional map.     

Some properties of three-periodic sphere packings

Some properties of sphere packings are reviewed. Candidates for the least-dense packings of one kind of sphere for different coordination numbers are identified and described. Some topological properties of sphere packing nets are also described.     

Controlled-Rate Thermal Desorptton

A new way of conducting thermal desorption experiments is described. The method consists in maintaining the desorption rate constant by a rigorous control of temperature. The equations for two models of constant rate desorption are described: from a surface with only one type of adsorption site, and with two different types. The technique is applied to two real systems and the kinetic parameters are determined. The results are compared with those obtained by using TPD. The main advantages are discussed and the methodology and modifications required for a TPD set-up to work at a constant desorption rate are described.     

The preparation and properties of 1,4-diazaphenoselenazine

The preparation and properties of 1,4-diazaphenoselenazine are described and compared with those of 1,4-diazaphenothiazine. Experiments leading to nitro and chloro derivatives and also ring-cleavage products of both the selenium and sulphur-containing heterocycles are also described.     

System for electrochemical studies with a four-electrode potentiostat

A four-electrode potentiostat and a system for electrochemical studies are described. The system is suitale for studies of an interface separating immiscible elecrolyte solutions by voltammetric, chronoamperometric and polarographric methods. The described systems are based on integrated operational amplifiers.     

Methan im Gashydrat. Gefangen im Wasserkäfig

This article shows the variety of gas hydrates regarding their occurrences, composition, characterization and potential usability. Synthetic clathrate hydrates are described as well as those hydrates occurring in nature. Different methods, embracing the spectrum from laboratory analytic methods to field use are described.     

Preparation of samples of plant material for chromatographic analysis

The selection, collection, and preliminary treatment of plant material samples are discussed. Stages of sample preparation and extraction techniques presently used are described, and the most recent examples of sample preparation for chromatographic analysis are reviewed. Recent applications of gas chromatography for the assessment of emission of volatile organic compounds by plants are also described.     

Adiabatic microcalorimeters for heat capacity measurement at low temperature

Technical problems in the design and construction of small sample adiabatic calorimeters are pointed out and solutions to them discussed. Two calorimeters constructed on the design principle are described with illustrative examples of data obtained with them. Hard and soft wares for fully automatic operation of the two calorimeters are described in some detail.     

Polymer films derived from aligned and polymerised reactive liquid crystals

The principles and methods of fabricating thin polymer films with particular optical properties via the process of in‐situ photopolymerisation of reactive liquid crystals are described. The optical properties of these films are described in terms of their retardation profile. Some possible applications, such as compensation films for improving the viewing angle of a TN‐TFT liquid crystal display are discussed. A novel way of combining the properties of a quarter wave foil and a compensation film for a broad band cholesteric brightness enhancement film is also described.     

Synthesis, characterisation and high-performance liquid chromatography of C6-C16 dicarboxylyl-mono-coenzyme A and -mono-carnitine esters.

The synthesis and purification of the mono-coenzyme A and mono-carnitine esters of the homologous series of straight-chain even-numbered dicarboxylic acids (C6-C16) is described. The corresponding 3-hydroxyacyl- and 2-enoyl-CoA esters were prepared enzymatically. A reversed-phase high-performance liquid chromatographic (HPLC) system for the analysis of the intact CoA esters is described and their chromatographic behaviour documented. Reversed-phase HPLC systems for the analysis of the 4-bromophenacyl derivatives of the dicarboxylyl-mono-carnitines and the 4-nitrobenzyl derivatives of the free acids are also described. Some preliminary studies of the metabolism of [U-14C]hexadecanedionoyl-mono-CoA by rat liver peroxisomes and rat skeletal muscle mitochondria are described illustrating the application of these methods.     

Preparation and properties of pure lithio esters of some carboxylic acids

Lithio esters of carboxylic acids have been prepared in pure state and their properties are described. Interaction between the lithio esters with alkali metals alkoxides has been demonstrated, and some adducts have been isolated. The IR and UV spectra of these compounds are described, and their structures are discussed.     

Preparation of hollow beads of poly(styrene-co-divinyl benzene)

Two methods are described for the production of hollow beads by copolymerization of styrene and divinyl benzene. Characterization of the beads is described and growth mechanisms proposed.     

The catalyst industry of Japan (2)

The trends of the catalyst industry in Japan are described based on the statistical data published by the Japanese government offices. Three topical items in the recent catalytic technology developments in Japan are described: resid FCC, methylmethacrylate, and emission control for lean-burn engines.     

Kinetic fluorimetric determination of cerium with 1,5-diphenyl-3-(2-stiryl)-Δ2-pyrazoline

A kinetic fluorimetric method for the determination of cerium(IV) (0.04–0.2 ppm) is described. The fluorescent species obtained results from oxidative transformation of the reagent. The reaction are described and the experimental variables and interferences in the determination are reported.