Preparation de membranes echangeuses de cations par photogreffage d'ethers allyliques du poly (alcool vinylique). Etude de certaines de leurs proprietes—II: Photogreffage des poly (alcools vinyliques) allyles

Poly(vinyl alcohols) partially allylated have been grafted with sulphonic acid. The influence of experimental parameters (vinyl sulphonic acid concentration, swelling before grafting, photoinitiator concentration, grafting temperature and duration of the irradiation) have been studied in detail.     

THE PHOTOMORPHOGENETIC CONTROL OF THE DEVELOPMENT OF PLASTID GLYCERALDEHYDE-PHOSPHATE DEHYDROGENASE AND PHOSPHORIBULOKINASE ACTIVITIES IN COTYLEDONS OF MUSTARD SEEDLINGS

The plastid glyceraldehyde-phosphate dehydrogenase and phosphoribulokinase of mustard cotyledon extracts were activated by preincubation with ATP and with ATP and dithiothreitol respectively. By in vitro activation prior to assay, it was possible to determine the potential activities, which appear to have been directly proportional to the amount of each enzyme protein present. In this way it was possible to deduce the net synthesis of these two enzymes. The induction of synthesis of glyceraldehyde-phosphate dehydrogenase and phosphoribulokinase, by continuous far red or white light were similar hut net synthesis in continuous far red continued longer for glyceraldehyde-phosphate dehydrogenase than for phosphoribulokinase. The kinetics of the development of the glyceraldehyde-phosphate dehydrogenase potential activity were very close to those reported by Bruning et al. (1975) for this enzyme. The data do not permit elimination of either the single switch or multiple switches hypotheses for the action of phytochrome. Continuous white illumination gave results similar to those for continous far red for the net synthesis of the two enzymes but it was more effective than far-red in bringing about enzyme activation in vivo.     

Quantum-chemical investigation of the influence of the vacant orbitals of the heteroatom on the shaping of the electronically excited states and luminescence-spectroscopic properties of triphenylgallium

The electronic structure of the triphenylgallium molecule in the ground and electronically excited states has been calculated in the framework of the CNDO/S-CI method in sp and spd bases. The electron density in the AO's and atoms, the first ionization potential the energies and matrices of the changes in the electron density of the S_n and T_n states, the matrix elements of the spin-orbit coupling operator $$ " align="middle" border="0"> and $$ " align="middle" border="0"> , the intensities and directions of polarization of the S_n S_o and T₂ T_n transitions, and the phosphorescence lifetimes have been calculated. The following spectroscopic parametrization has been proposed for the Ga atom in the sp and spd bases: 1/2(I_s + a_s) = 10.075 eV, 1/2(I_p + A_p) = 4.265 eV, 1/2(I_d + A_d)=0, _Ga ^p =5 eV, _Ga ^d =O, _Ga ^sp =–7 eV, _Ga ^spd =–10 eV, and _s,p,d=1.433. The influence of the d AO's on the shaping of the orbital nature of the S₁ and T₂ states has been analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 584–590, September–October, 1985.     

Ion-pair extraction of pentacaine from biological materials

Simple and rapid extraction method for quantitative and selective isolation of the new local anesthetic pentacaine from biological materials is proposed. The technique of ion-pair formation was found to be more effective than usual access using the extraction of the nonionized species. The extraction yield of the unchanged molecule³H-pentacaine after double extraction and single scrubbing was found to be more than 90%. The radiochemical purity was over 90%. The method appears suitable for pharmacokinetic studies in the animal body.     

An evaluation of cellulose as a substrate for room-temperature phosphorescence

Cotton-linter pulps, wood pulps and several filter papers have been evaluated as substrates for room-temperature phosphorescence. A variety of chemical treatments of one filter paper is discussed in terms of reducing the background phosphorescence of the cellulose and in evaluating possible trace contaminants in cotton fibres. In order to account for uniformity of filter paper used in room temperature phosphorescence, a final evaluation of several different lots of one type of filter paper is presented.     

Computational modeling of amorphous silica. 4. Modeling the initial structures. Aerogel

A qualitative classification algorithm for constructing large clusters of aerogel model structures is used. According to this algorithm, aerogel is classified with polysilicas characterized by a packing of long chains of silicon-oxygen tetrahedra. A model of the aerogel structure is suggested, according to which aerogel is described as a set of cross-linked chains forming double or more complex ribbons. This model is in agreement with the conclusions drawn from analysis of the vibration spectra of its components. Institute of Surface Chemistry, Ukrainian Academy of Sciences. Russian University of Peoples' Friendship. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 35–38, May–June, 1994. Translated by O. Kharlamova     

Concise synthesis of acyl migration-blocked 1,1-difluorinated analogues of lysophosphatidic acid

Lysophosphatidic acid (LPA, 1- or 2-acyl-sn-glycerol 3-phosphate) is an important phospholipid mediator produced by activated platelets and by ovarian cancer cells. Efforts to understand LPA signaling through G-protein-coupled receptors are hampered by the facile acyl migration that results in equilibration to a mixture of the 1- or 2-acyl species under physiological conditions. We describe a new and efficient route to enantiomerically homogeneous lysophospholipid analogues from D-mannitol 1,2:5,6-bis-acetonide to give two 1,1-difluorodeoxy analogues of (2R)-acyl-sn-glycerol 3-phosphate. These compounds are migration-blocked analogues of the labile sn-2 LPA species. The (19)F NMR of diastereotopic fluorines of the difluoromethyl group shows an unexpected solvent dependence.     

Biomimetic dyes as affinity chromatography tools in enzyme purification

Affinity adsorbents based on immobilized triazine dyes offer important advantages circumventing many of the problems associated with biological ligands. The main drawback of dyes is their moderate selectivity for proteins. Rational attempts to tackle this problem are realized through the biomimetic dye concept according to which new dyes, the biomimetic dyes, are designed to mimic natural ligands. Biomimetic dyes are expected to exhibit increased affinity and purifying ability for the targeted proteins. Biocomputing offers a powerful approach to biomimetic ligand design. The successful exploitation of contemporary computational techniques in molecular design requires the knowledge of the three-dimensional structure of the target protein, or at least, the amino acid sequence of the target protein and the three-dimensional structure of a highly homologous protein. From such information one can then design, on a graphics workstation, the model of the protein and also a number of suitable synthetic ligands which mimic natural biological ligands of the protein. There are several examples of enzyme purifications (trypsin, urokinase, kallikrein, alkaline phosphatase, malate dehydrogenase, formate dehydrogenase, oxaloacetate decarboxylase and lactate dehydrogenase) where synthetic biomimetic dyes have been used successfully as affinity chromatography tools.     

Determination of low levels of an antioxidant in polyolefins by large-volume injection temperature-programmed packed capillary liquid chromatography

Sub-ambient column temperatures, promoting strong interactions between the analyte and the stationary phase material, were utilized to focus large volumes of the polyolefin antioxidant Irganox 1076 [benzenepropanoic acid, 3.5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester] on the column inlet, using pure acetonitrile as sample solvent and mobile phase. Injection volumes up to 100 microl were successfully employed on a 50 cm x 320 microm I.D. capillary column packed with 5 microm Kromasil 100 ODS particles. Irganox 1076 was eluted after completed injection by temperature programming, using a temperature program from 7 to 90 degrees C, in 3 degrees C min(-1). UV detection, using a low-dispersion "U"-shaped flowcell, was performed at 280 nm. The method was applied for the determination of Irganox 1076 that was extracted from low-density polyethylene (0.6 ppm, w/w). Both Soxhlet and microwave-aided solvent extractions were performed, using chloroform and acetonitrile as solvents, respectively. The microwave-aided extraction with acetonitrile was found to give approximately the same yield as the standard Soxhlet reference method. Consequently, small volumes of acetonitrile could be used both as extraction solvent, sample solvent and mobile phase, simplifying the analysis process. The mass limit of detection of the method was found to be 3.3 ng, corresponding to a concentration limit of detection of 33 ng ml(-1), utilizing an injection volume of 100 microl. The within and between day precision of retention times displayed relative standard deviations below 1.2%.     

Stereochemical effects in the electron impact mass spectra of cis–trans isomeric 1,2,3,5-tetramethylcyclohexanes and some trimethylcyclohexanes

The mass spectra of 10 isomeric trimethylcyclohexanes and six cis–trans isomeric 1,2,3,5-tetramethylcyclohexanes are discussed. The thermochemically stable isomers show a higher abundance of the [M? CH₃]⁺ ions and a lower abundance of the [M? C₂H₅]⁺ ions than the strained isomers. The log of the intensity ratio for loss of methyl and ethyl from the molecular ions correlates well with the strain energies and with the mean number of gauche arrangements of the stereoisomers.