Purification and properties ofClostridium thermocellum endoglucanase 5 produced inEscherichia coli

Endoglucanase 5 (EG5) has been isolated from the strain ofE. coli TGI harboring recombinant plasmid pCU108, which contains thecel5 gene ofC. thermocellum. The enzyme has been produced with 98-fold purification and a final yield of 27% by using subsequent twofold high performance ion-exchange chromatography on Mono Q and high performance chromatofocusing on Mono P. The protein has a mol mass of 35 kDa and includes 3 multiple forms with pI 4.4–4.8 as evidenced by analytical gel isoelectrofocusing. EG5 cleaves CMC (K_m = 0.097 g/L, V_max = 8.2 mg/min·mg of protein), amorphous cellulose, xylan, lichenan as a substrate with an optimum temperature of 80?C and pH 6.0 and Avicel (K_m = 18.2 g/L, V_max = 0.035 mg/min·mg of protein) with an optimum temperature of 60?C and pH 6.O. Cellobiose in concentrations up to 200 Μg/mL do not inhibit the hydrolysis of CMC by EG5, but 10–30 Μg/mL of glucose significantly decrease the activity of this enzyme. The stimulating role of calcium chloride and concentration of protein in the system has been demonstrated for Avicel hydrolysis by EG5.     

Analytical methods for water supply systems

Summary An analytical system for monitoring and controlling water treatment plants is presented. The single measuring devices (flow, temperature, turbidity, pH, pCl, conductivity, COD, pressure difference, alkalinity, hardness, free chlorine) are described.

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Analytische Methoden für Wasserversorgungseinrichtungen

Zusammenfassung Ein analytisches System zur Überwachung und Steuerung von Wasseraufbereitungsanlagen wird vorgestellt. Die einzelnen Meßstellen (Fließgeschwindigkeit, Temperatur, Trübung, pH, pCl, Leitfähigkeit, CSB, Druckdifferenz, Alkalität, Härte, freies Cl₂) werden beschrieben.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Synergism betweenClostridiwn Thermocellum cellulases cloned inEscherichia coli

We have obtained a synergistic effect during degradation of Avicel and filter paper by Clostridium thermocellum cellulases (two endoglucanases and one cellobiohydrolase) cloned in Escherichia coli. The highest degree of synergism was found at early stages of reaction, during the first 20 h: 2.5 and 2.9 on Avicel and filter paper, respectively. During combined action of all three cellulases the main product is cellobiose.     

The role of the alien proton acceptor on the formation of LC structure in H-bonded monomeric and polymeric derivatives of alkoxybenzoic acids

The formation of the complex between 4-cyanopyridine and 4-(6-acryloyloxy-hexyloxy) benzoic acid and its polymeric analog proceeds due to the proton transfer with the H-bond formation. The presence of two proton acceptor groups within one molecule provides a strong shift of the electron density along the complex molecule due to the conjugation within the proton acceptor molecule. The dielectric relaxation process in a symmetric associate experimentally observed is explained as a kinetic effect related to the formation and destruction of the associate.

Transition from a monomer to a polymer proton donor leads to the formation of the characteristic 1:1 complex with SmC layered structure different from that of a polymer itself.     

A new catalytic reaction of rhenium and its analytical application

Small amounts of perrhenate in fairly concentrated sulphuric acid media and in the presence of tin(II) chloride are found to catalyse the acid hydrolysis of alpha-furildioxime, with production of a new absorption peak at 320 nm, due to the di-alpha-furildiketone produced. The catalytically active species is a sulphate complex of rhenium(IV). The catalytic action of rhenium is promoted by citric acid. Rhenium can be determined in the range 0.0005-0.5 mug/ml. Interferences are eliminated by a preliminary extraction. The method has been applied to the determination of rhenium in copper concentrates of low rhenium content, copper ores and rocks. On the basis of the inhibitory effect of molybdenum the reaction can be used for determination of this element as well.     

Reactions of 2-Arylthio- and 2-Arylsulfonyl-1-nitro-1-phenylethenes with Amines

2-Arylthio- and 2-arylsulfonyl-1-nitro-1-phenylethenes react with amines to give the corresponding nitroenamines whose configuration (E or Z) depends on the amine structure. Primary amines gives rise to Z-nitroenamines, secondary cyclic amines with 2-arylthio-1-nitroalkenes form E-nitroenamines, and with more reactive 2-arylsulfonyl-1-nitroalkenes E/Z-isomeric mixtures are obtained.     

Pyramidane and isoelectronic pyramidal cations

Ab initio STO-3G, 4-31G and semi-empirical MINDO/3 calculations were performed on a series of C₄H₄X compounds to analyze the possibility of existence of their nonclassical C_4V pyramidal isomeric forms. It was shown that with the four-electron group X (C, N⁺, P⁺, O²⁺, S²⁺) in an apex, C_4V pyramidal structures are indeed stable, i.e., conform to local minima on the corresponding potential energy surfaces. Relative energies, molecular geometries and charge density distribution for various isomeric forms of the C₄H₄X compounds are presented. The theoretically derived strategies for an experimental trapping of the pyramidane 1, X = C and the C_4V pyramidal thiophene dication 1, X = S²⁺ are discussed.     

A Chain Catalytic Reaction Involving Pd Cluster as Chain Carrier

   α−Alkyl- and α,α′-dialkyl-substituted benzylic alcohols PhCR′R′′OH (R′=H, Me, Et, Bu; R′′=H, Me) are transformed to the corresponding dilbenzylic ethers and water in acid-free neat substrate media shortly after the addition of the palladium(I) cluster [Pd₄(CO)₄(OAc)₄] (1). During the catalytic reaction occurring under anaerobic conditions, cluster 1 is gradually decomposed to form Pd black, whereas neither original cluster 1 nor Pd black is responsible for the observed reaction. The true reaction catalyst is generated from cluster 1 after a short induction period. On the basis of the reaction kinetics and the HREM, X-ray diffraction, DTA-TG, and elemental analysis data, the catalytic dehydration is suggested to occur through a nonradical chain mechanism involving an unstable intermediate Pd cluster as the chain carrier.

Synthesis of derivatives of 7,8-dihydrothiazolo[2,3-<Emphasis Type="Italic">i</Emphasis>]purine by halocyclization of 6-allylthiopurine

7-Halomethyl-7,8-dihydrothiazolo[2,3-i]purines were synthesized by the reaction of bromine and iodine with 6-allylthiopurine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1551–1553, October, 2004.     

Aqueous electrochemistry of binuclear copper complex with Robson-type ligand: dissolved versus surface-immobilized reactant

The electrochemical behaviour of binuclear copper complex with Robson-type ligand [Cu₂L]Cl₂ in aqueous medium is studied by cyclic voltammetry at highly oriented pyrolytic graphite, glassy carbon and gold electrodes. The overall reduction from solution of this reactant is found to be irreversible resulting in metallic copper formation. It is also complicated by chemical transformations of Cu(I) containing species. When attached to carbon support, [Cu₂L]Cl₂ is redox active in aqueous medium in the same potential range. The reduction is more reversible if reactant is immobilized at HOPG surface, and is in general agreement with reversible copper demetallation scheme. For dissolved reactant, the contribution of surface-attached species is screened by predominating voltammetric response of irreversible reduction. These conclusions are supported by data on the reduction of free protonated ligand and its hydrolysis products. Ex situ STM is applied to characterize electrode surfaces modified by [Cu₂L]Cl₂. Adsorbate monolayer of periodic structure is observed at highly oriented pyrolytic graphite (HOPG). Adsorption is more disordered at GC and less strong at polycrystalline gold support.