Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS)

An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant K(o), thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.     

Spectrophotometric determination of traces of selenium(IV) in various environmental samples using the flow-injection technique (FIT)

A simple, sensitive, and rapid flow-injection spectrophotometric method was developed for the determination of trace amounts of selenium(IV). The method is based on the oxidation reaction of 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) by selenium(IV) followed by the coupling reaction with chromotropic acid (4.5-dihydroxy naphthalene-2.7-disulphonic acid) in a basic medium (phosphate buffer, pH 10.5) to give a pink derivative with λ_max 530 nm that is stable for more than 7 days at 35°C. The reaction and flow conditions of the full experimental design were optimized. A detection limit (2s) of 0.25 μg/L Se(IV) was obtained at a sampling rate of 10 samples per hour. Beer’s law is obeyed for a Se(IV) concentration range of 0.05–0.5 μg/mL at the wavelength of maximum absorption. The detailed study of various interference ions indicates that the method is highly selective. The method was successfully applied to the determination of traces of selenium(IV) in various water samples. The results obtained were in good agreement with those obtained by the reported methods at the 95% confidence level. The text was submitted by the authors in English.     

Kinetics of substitution of aquo ligands fromcis-diaquo-bis-(biguanide) cobalt(III) and chromium(III) ions by aspartic acid in ethanol—water mixtures

The kinetics of substitution of aqua ligands fromcis-diaqua-bis(biguanide)cobalt(III) and chromium(III) ions by aspartic acid in EtOH–H₂O media have been studied spectrophotometrically in the 30 to 45°C range. We propose the following rate law for the anation

Synthesis,crystal structure and luminescent property of a novel H<Subscript>2</Subscript>O-bridged cobalt(II) polymer with one-dimensional chain structure

The coordination compound [Co(C₁₀H₇COO)₂(H₂O)₃]_2n · 4nH₂O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions. The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can be assigned to the intraligand electronic transfer.     

Silica-alumina supported transition metal oxide catalyst for alkylation of aromatic compounds

Titanium oxide on silica-alumina support is described to be an efficient regenerable catalyst for alkylation of aromatic compounds with alkyl halides, alcohols and olefins, and the reaction is proposed to be initiated by the protonated metal active species present in the catalyst.     

Conversion of 3-benzoyl-1-methyl-4-phenyl-γ-piperidol by arylamines and arylhydrazines. Synthesis of 3-arylamino-1-oxo-1-phenylpropanes and 1,3-diarylpyrazoles and their fragmentation under electron impact

It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007.     

The Effect of Alkane Chain Length on the Liquid–Liquid Critical Temperatures of Oligostyrene/Linear-Alkane Mixtures

Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N ₁=5) to pentacontane (N ₁=50)) with an oligostyrene (1241amu, N ₂=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains.     

On the characterization of electrified interface

Summary Estimation of zeta potential from experimental data on electroosmotic and electrophoretic effects for Zeokarb 225 (Na⁺ form)/methanol-water system has been made and discussed. Results indicate that zeta potentials estimated from electroosmotic flux and electrophoretic mobility are not in agreement and vary with applied potential difference in a linear manner. Reasons for the variation of zeta potential with electrical field have been discussed. It has been argued that zeta potentials estimated from electroosmotic data are more reliable in comparison to the values obtained from electrophoretic data.With 2 figures and 2 tables     

Solution- and solid-phase synthesis of natural product-like tetrahydroquinoline-based polycyclics having a medium size ring

A solid-phase synthesis of tetrahydroquinoline-derived polycyclic 4, having a medium size ring with an enamide functionality, was achieved from tetrahydroquinoline derivative 3 in five steps with overall 40-45% yield. An enantiopure, tetrahydroquinoline-derived beta-amino ester, 1, was converted into compound 2 that has a free phenolic hydroxyl group as an anchoring site for solid-phase synthesis. The solid-phase worked well for this sequence, in which the synthesis of the unsaturated eight-membered enamide lactam was obtained by a ring-closing metathesis approach. Compound 4 is a novel, natural product-like polycyclic derivative that could further be utilized in library generation for developing small molecule chemical probes.     

Experiments in Solving Mixed Integer Programming Problems on a Small Array of Transputers

The time-consuming process of solving large-scale Mixed Integer Programming problems using the branch-and-bound technique can be speeded up by introducing a degree of parallelism into the basic algorithm. This paper describes the development and implementation of a parallel branch-and-bound algorithm created by adapting a commercial MIP solver. Inherent in the design of this software are certain ad hoc methods, the use of which are necessary in the effective solution of real problems. The extent to which these ad hoc methods can successfully be transferred to a parallel environment, in this case an array of at most nine transputers, is discussed. Computational results on a variety of real integer programming problems are reported.