Carbohydrates of allium IX. Polysaccharides of A. suvorovii

The carbohydrate compositions of all the organs ofAllium suvorovii Rgl have been determined and it has been established that the bulk of the fructose accumulates in its bulbs. The dynamics of the accumulation of glucofructans in the bulbs has been studied and it has been found that this accumulation is a maximum in the dormancy stage.     

Carbohydrates of allium IX. Polysaccharides of A. suvorovii

The carbohydrate compositions of all the organs ofAllium suvorovii Rgl have been determined and it has been established that the bulk of the fructose accumulates in its bulbs. The dynamics of the accumulation of glucofructans in the bulbs has been studied and it has been found that this accumulation is a maximum in the dormancy stage.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedienii, No. 6, pp. 622–624, November–December, 1992.     

Stoffwechselprodukte von Mikroorganismen. 50. Mitteilung. Die Konfiguration der Arcanose

The L -xylo configuration of arcanose, a sugar from the antibiotic lankamycin, has been proven by its transformation into cladinose. The determination of the absolute configuration at C-3 of arcanose and cladinose has been accomplished utilizing a new procedure.     

Polysaccharides of the protein-lipoid-polysaccharide complex of the mycelium ofVerticillium dahliae. I. Isolation and fractionation

A phytotoxic PLPC has been isolated from the mycelium of the fungusVerticillium dahliae Kleb., strain 614. The polysaccharide component has been split out from the PLPC by mild acid hydrolysis. The polysaccharide has been fractionated and the monosaccharide compositions of the fractions have been determined. A phytotoxic polysaccharide homogeneous according to gel chromatography and chromatography on DEAE-cellulose has been isolated which consists of an α-glucan containing a minor amount of D-glucosamine.     

Photochemistry of imidazolides. I. The photo-Fries-type rearrangement of N-substituted imidazoles.

A number of N-substituted imidazoles 1a–1i have been found to photo-isomerize to give the corresponding 2-substituted- and 4(or 5)-substituted imidazoles ( 2a–2i and 3a–3i ). The role of a dissociative path in these reactions has been demonstrated.     

Diterpenoids ofPulicaria salviifolia. III. The structure of salvicinin

The new diterpene acid salvicinin has been isolated from the epigeal part ofPulicaria salviifolia and its structure has been established as 15-acetoxy-6α-hydroxy-trans-cleroda-3,13-dien-19-oic acid. A capacity of salvicinin for undergoing lactonization in the presence of acetic anhydride has been revealed, and the lactone formed has been isolated and chracterized.     

Polysaccharides of Polygonatum. VII. A glucofructan from P. sewerzowii

A glucofructan has been isolated from the rhizomes ofPolygonatum sewerzowii Bunge and has been called pseverin. According to its chemical and spectral characteristics, pseverin is a polysaccharide containing both inulin, 2 1, and leven, 2 6, glycosidic bonds. The problem of the correlation between the molecular structure of a glucofructan and its supermolecular organization has been considered. X-radiographic and electron-microscope studies have been made of pseverin and its acetate. It has been established that on precipitating from solution pseverin forms globular particles which aggregate to give elongated necklace-like formations. Fine lamellar structures are characteristic for the acetate.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–20, January–February, 1986.     

Triterpene glycosides ofAstragalus and their genins. XXI. Circular dichroism of cycloartane ketones

The CD spectra of a number of natural and synthetic cycloartane ketones have been studied. The influence of 6α-hydroxy group on the Cotton effect due to a 3-keto function has been found. The Cotton effect has been determined for 6-oxo-and 11-oxocycloartanes.     

Rubbing-induced surface textures in nematic MBBA layers and their behaviour under applied d.c. or a.c. voltages

Surface irregularities (for example, rubbing-induced domains, and bumps) have been observed in MBBA nematic cells after special treatment of the electrodes using a conventional soap. Various techniques such as polarizing microscopy, the shadowgraph technique and computer processing of the images have been used. The behaviour of the rubbing-induced domains under a.c. or d.c. electric fields has been studied. A new flexoelectric effect has been observed leading to the dividision of the rubbing-induced domains. A simple model has been proposed (a modification of the Saupe model), which explains the structure and dividision of the rubbing-induced domains.     

Rubbing-induced surface textures in nematic MBBA layers and their behaviour under applied d.c. or a.c. voltages

Surface irregularities (for example, rubbing-induced domains, and bumps) have been observed in MBBA nematic cells after special treatment of the electrodes using a conventional soap. Various techniques such as polarizing microscopy, the shadowgraph technique and computer processing of the images have been used. The behaviour of the rubbing-induced domains under a.c. or d.c. electric fields has been studied. A new flexoelectric effect has been observed leading to the dividision of the rubbing-induced domains. A simple model has been proposed (a modification of the Saupe model), which explains the structure and dividision of the rubbing-induced domains.     

Halogenation of polyethylene. I. Bromination of single crystals

It has been demonstrated that the fold surfaces of polymers can be specific towards chemical attack, if the reaction is mild and nondestructive of the fold. Bromination of suspensions of single crystals of polyethylene in carbon tetrachloride has been shown to be such a system. This chemical modification of a fold surface is a powerful means of extending the applications of the physical methods available. Several methods were used, among them DTA, DSC, infrared spectroscopy and small-angle x-ray diffraction. Experimental results from these methods lead to the following conclusions. (a) Bromination takes place preferentially at the folds and is consistent with a regular adjacent reentry fold model. (b) Annealing of these brominated crystals demonstrates the major role played by the crystal surface in this process. (c) The preparation and properties of a novel copolymer system has been demonstrated. It is felt that this copolymer system may prove a useful addition to those systems presently available.     

Solution Properties of Polyelectrolytes. VI. Secondary Effects in Aqueous Size-Exclusion Chromatography

Abstract

An independent analysis of different operational variables in aqueous size exclusion chromatography of poly electrolytes has been carried out using a silica-based support. The effect of polyion concentration, pH and ionic strength on sodium polystyrenesulfonate calibration plots has been investigated. Finally, a novel semi-empirical model has been developed from thermodynamic considerations which relates the support effective pore volume to the polyelectrolyte molecular weight and qualitatively describes secondary effects.     

Structure of diepoxide–diamine network polymers. II. Soluble chemical species

Gel permeation chromatography has been used to separate diepoxide–diamine oligomers, produced at a variety of stoichiometric ratios, into individual chemical species. Probability theory has been applied to calculate expressions for the amounts of each of these compounds and close agreement has been found with the experimental results. In conjunction with previous conclusions, this provides compelling evidence in favor of a purely random reaction mechanism, contrary to the inhomogeneous network-forming mechanism suggested by other workers. The effect of adding an inert diluent prior to reaction has been investigated and it is evident that the fraction of intramolecularly formed bonds increases as the concentration of polymer decreases.     

Alkaloids ofNitraria komarovii. V. Structure and synthesis of komarovicine

The new alkaloid komarovicine has been isolated from the epigeal part of the plantNitraria komarovii Iljin et Lava. Its structure has been established on the basis of spectral and experimental results and its synthesis has been performed. A transition has been made to the alkaloids komarovine and komarovidine isolated previously.     

A new type of d.c. arc as spectrochemical light source

A new type of d.c. arc light source for spectrochemical purposes has been developed. The horizontal arc burning in a graphite tube is placed in an inhomogeneous magnetic field. The limits of detection of In and Pb have been determined. The temperature distribution between the electrodes and the tube wall has been measured.     

Berberis alkaloids. XXIV. Structure of bernumine

Bernumine, which belongs to a new group of N-benzyltetrahydroisoquinoline alkaloids, has been isolated from the leaves of Berberis nummularia Bge. Its structure has been established on the basis of spectral characteristics and chemical transformations.     

Studies on bulk polymerization of methyl methacrylate. I. Thermal polymerization

The thermal bulk polymerization of methyl methacrylate (MMA) in a wide range of temperatures has been studied using a dilatometric reactor. It is shown that, irrespective of the care taken to purify the MMA, the evolution of the time-conversion curve can be explained only if we account for the presence of an impurity associated with the monomer acting as a free radical initiator. The activation energy for the decomposition of this impurity has been estimated as 98 kJ/mol. Having accounted for this impurity, the activation energy for the real thermal polymerization of the MMA has been estimated to be 75 kJ/mol. © 1993 John Wiley & Sons, Inc.     

Diazepines. V. The reaction of homophthalic anhydride with hydrazines

The reaction of homophthalic anhydride with hydrazine and a number of substituted hydrazines has been investigated. Only in the case of the reaction of homophthalic anhydride and 1,2-dimethylhydrazine has a diazepine been isolated. The previously reported (2) diazepine from homophthalic anhydride and hydrazine appears to be a product resulting from the reaction of twomolec of homophthalic anhydride with one mole of hydrazine.     

HPLC of nucleotides. II. General methods and their development for analysis and preparative separation. An approach to selectivity control

In order to develop efficient separation methods for nucleotides according to their size and heterocyclic composition, the application of ion-exchange, reverse-phase, and normal-phase adsorption HPLC has been studied. The comparative investigation of retention power and selectivity of various packings (non-polar bonded-phase and amino silicas) in relation to nucleotide length and composition yields data which enable suitable packings to be selected and a method of preparing the new packing for a particular separation problem to be formulated. Thus a new anion exchanger with high selectivity and dynamic mass transfer has been prepared for fractionation of large oligonucleotides. The effect of the eluent pH and composition (organic modifier, salt) on retention, selectivity, and resolution in ion-exchange and reverse-phase HPLC has been studied. The optimum separation conditions comprise elution with oppositely directed gradients of the salt and the modifier, use of a precolumn packing that provides the best protection for the main column without loss of its efficiency, and the optimum gradient program for the desired retention of the component of interest. The relation between loading and sample concentration has been studied and the system for gradient elution improved. Our work shows that two-dimensional separation is the most reliable and informative method for preparation of homogeneous oligonucleotides. The hydrophobic-pair ion-exchange mechanism is proposed for ion-pair chromatography. Protected and partially deblocked oligonucleotides, chemically synthesized for genetic engineering studies, have been separated with high selectivity by adsorption (normal-phase) HPLC which is efficient for gradient elution with isohydric eluents. The analysis of a monomeric composition of nano-(pico-) molar amounts of oligonucleotides has been developed; the procedure involves microcolumn digestion of the oligonucleotides with immobilized enzymes followed by microcolumn separation of the nucleoside-mononucleotide mixture. Also, a new slurry method for packing stable HPLC columns with a tightly consolidated, nonshrinkable bed of particles has been developed.