A microcalorimetric study of the toxicity of two cobalt compounds on <Emphasis Type="Italic">Escherichia coli</Emphasis> DH5α growth

Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II) (denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)³⁺) on (E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output P _m and the time (t _m) corresponding to the P _m were obtained. The half-inhibitory concentrations (IC₅₀) of Co(II) and Co(sep)³⁺ to E. coli DH5α were 15 and 42.1 mg mL⁻¹, respectively. The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)³⁺. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)³⁺. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)³⁺ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique.     

Immobilization of <Emphasis Type="Italic">Escherichia coli</Emphasis> novablue γ-glutamyltranspeptidase in Ca-alginate-<Emphasis Type="Italic">k</Emphasis>-carrageenan beads

The recombinant Escherichia coli gamma-glutamyltranspeptidase (EcGGT) was immobilized in Ca-alginate-kappa-carrageenan beads. Effects of alginate concentration, amount of loading enzyme, and bead size on the entrapped activity were investigated. Optimum alginate concentration for EcGGT immobilization was found to be 2% (w/v). Using a loading enzyme concentration of 1.5 mg/g alginate, maximum enzyme activity was observed. With increase in bead size from 1.9 to 3.1 mm, the immobilization efficiency was decreased significantly because of mass transfer resistance. Thermal stability of the free EcGGT was increased as a result of the immobilization. Ca-alginate-kappa-carrageenan-EcGGT beads were suitable for up to six repeated uses, losing only 45% of their initial activity. Upon 30 days of storage the preserved activity of free and immobilized enzyme were found as 4% and 68%, respectively. The synthesis of L: -theanine was performed in 50 mM Tris-HCl buffer (pH 10) containing 25 mM L: -glutamine, 40 mM ethylamine, and 1.5 mg EcGGT/g alginate at 40 degrees C for 12 h, and a conversion rate of 27% was achieved.     

<Emphasis Type="Italic">N</Emphasis>′-tetrazolylmethoxyl derivatives of <Emphasis Type="Italic">N</Emphasis>-methyldiazene <Emphasis Type="Italic">N</Emphasis>-oxides

A preparation method was developed for previously unknown tetrazole derivatives containing in the 1, 2, and/or 5 positions of the tetrazole ring N-methyldiazene-N-oxide-N′-oxymethyl groups.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> adhesion to surfaces–a thermodynamic assessment

Several studies have tried to correlate bacterial adhesion with the physicochemical properties of the surface with limited success. Most often, the obtained correlations seem to be only applicable to a particular set of experimental conditions making it difficult to obtain guidelines for the design of antibiofouling surfaces. The ratio between Lifshitz van der Waals apolar component and the electron donor component (γ^LW/γ^?) was recently shown to correlate with bacterial adhesion to the surfaces of ship hulls and heat exchangers. In this work, four materials with biomedical application (polystyrene, poly-l-lactide, cellulose acetate, and polydimethylsiloxane) and glass were characterized and Escherichia coli adhesion to those materials was assayed with a parallel-plate flow chamber operating in physiological shear stress conditions. Adhesion was correlated with the γ^LW/γ^? ratio, further extending the application range tested on the original study. Additionally, results from other studies were also evaluated to confirm the applicability of this correlation to other surfaces, microorganisms, and experimental conditions. Results show that bacterial adhesion is reduced in surfaces with lower γ^LW/γ^?and enhanced otherwise. This finding may be helpful in the design of new coatings by controlling γ^LW/γ^? or in the selection of existing materials according to the desired application.     

Synthesis of 20<Emphasis Type="Italic">S</Emphasis>-protopanaxadiol <Emphasis Type="Italic">β</Emphasis>-D-galactopyranosides

20S-Protopanaxadiol (3β,12β,20S-trihydroxydammar-24-ene) 3-, 12-, and 20-O-β-D-galactopyranosides were synthesized for the first time. Condensation of 12β-acetoxy-3β,20S-dihydroxydammar-24-ene (1) and 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosylbromide (α-acetobromogalactose) (2) under Koenigs–Knorr conditions with subsequent removal of the protecting groups resulted in regio- and stereoselective formation of 20S-protopanaxadiol 3-O-β-D-galactopyranoside, an analog of the natural ginsenoside Rh₂. Glycosylation of 12β,20S-dihydroxydammar-24-en-3-one (5) by 2 with subsequent treatment of the reaction products with NaBH₄ in isopropanol and deacetylation with NaOMe gave 20S-protopanaxadiol 12- and 20-O-β-Dgalactopyranosides.     

10<Emphasis Type="Italic">α</Emphasis>-Hydroxy-<Emphasis Type="Italic">β</Emphasis>-isomorphine,a by-product of the synthesis of 10<Emphasis Type="Italic">α</Emphasis>-hydroxymorphine

Abstract  A new compound was isolated from the reaction mixture after O-demethylation of 6-O-acetyl-10α-acetoxycodeine with boron tribromide. The structure of this compound, 10α-hydroxy-β-isomorphine, was elucidated by spectral data, and its spatial arrangement was deduced from an NOE experiment. Capillary zone electrophoresis was used for separation of morphine and its 10-hydroxy analogues. Graphical abstract        

Directed Aminomethylation of Pyrrole,Indole, and Carbazole with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N′</Emphasis>,<Emphasis Type="Italic">N′</Emphasis>-Tetramethylmethanediamine

Catalytic aminomethylation of pyrrole and indole with N,N,N′,N′-tetramethylmethanediamine in the presence of 5 mol % of ZrOCl₂·8H₂O proceeds selectively at the positions 2, 5 of pyrrole and 1, 3 of indole. Carbazole under the same conditions affords 3-formyl-9-aminomethyl derivative. The reaction in the presence of 5 mol % of K₂CO₃ occurs as monoaminomethylation: for pyrrole at the position 2, for indole at the position 3, and for carbazole at the nitrogen atom of the substrate. Water-soluble 1,1′-(1H-pyrrole-2,5-diyl)bis(N,N-dimethylmethanamine) exhibits a fungistatic activity with respect to phytopathogenic fungi Rhizoctonia solani.     

Synthesis of <Emphasis Type="Italic">α</Emphasis>-chloropyridine derivatives of <Emphasis Type="Italic">γ</Emphasis>-aminobutyric acid

The sodium salt of N-(6-chloronicotinoyl)-γ-aminobutyric acid, a structural analog of the known nootropic and vasidilating drug picamilon, was synthesized via Schotten–Baumann acylation of γ-aminobutyric acid with 6-chloronicotinoyl chloride and subsequent neutralization of the N-(6-chloronicotinoyl)-γ-aminobutyric acid that was obtained in >60% yield.     

Expression of a Glucose-tolerant β-glucosidase from <Emphasis Type="Italic">Humicola grisea</Emphasis> var. <Emphasis Type="Italic">thermoidea</Emphasis> in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

A β-glucosidase gene (bgl4) from Humicola grisea var thermoidea was successfully expressed in Saccharomyces cerevisiae. The recombinant protein (BGL4 ^Sc ) was initially detected associated with yeast cells and later in the culture medium. BGL4 ^Sc showed optimal pH and temperature of 6.0 and 40 °C, respectively, and an apparent molecular mass of 57 kDa. The enzyme showed activity against cellobiose and synthetic substrates, and was inhibited more than 80% by Fe²⁺, Cu²⁺, Zn²⁺, and Al³⁺. Using p-nitrophenyl-β-d-glucopyranoside (pNPG) as substrate, BGL4 ^Sc presented a V _max of 6.72 μmol min⁻¹ mg total protein⁻¹ and a K _m of 0.16 mM under optimal conditions. Most important, BGL4 ^Sc is resistant to inhibition by glucose and the calculated K _i value for this sugar is 70 mM. This feature prompts BLG4 ^Sc as an ideal enzyme to be used in the saccharification process of lignocellulosic materials for ethanol production.     

An efficient synthesis of <Emphasis Type="Italic">β</Emphasis>-methoxycarbonyl-<Emphasis Type="Italic">γ</Emphasis>-butyrolactones

β-Methoxycarbonyl-γ-butyrolactones bearing a γ-aromatic substituent were prepared via copper-catalyzed reductive aldol addition/lactonization domino reactions of ketones with α,β-unsaturated dicarboxylate esters and a silane under ambient temperature. The reaction has advantage of using readily available reagents, mild conditions and high efficiency.     

<Emphasis Type="Italic">β</Emphasis>-Chloro-<Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">β</Emphasis>-unsaturated carbonyls as convenient precursors of highly substituted benzenes

The Diels–Alder reactions of three β-chloro-α,β-unsaturated carbonyl compounds 1–3 with different dienes were carried out to afford highly functionalized cyclohexenes 4–9, bearing quaternary centers, in good yields. These cycloadducts (CAs) undergo dehydrochlorination with subsequent aromatization in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene DBU to produce new substituted benzenes 11–14. Compound 10 is the product of lactonization and removal of an HCl molecule from compound 7. All products were characterized by NMR, IR, elementary analysis and some of them by MS. Structure assignments of isomers were carried out on the basis of NMR chemical shifts and coupling constants using 1D, 2D and heteronOe NMR techniques.     

Influence of the force interaction on accumulation of macroscopic correlations in elementary reaction <Emphasis Type="Italic">A</Emphasis> + <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">C</Emphasis>

The applicability of the Encounter Theory (ET) (the prototype of the Collision Theory) concepts for widely occurring diffusion assisted irreversible bulk reaction A + B →C (for example, radical reaction) in dilute solutions taking account of initial microscopic correlations and force interactions between reactants has been treated theoretically with modern many-particle method for the derivation of non-Markovian binary kinetic equations. The method shows that taking into consideration initial correlations and force interactions leads to the redefinition of the Markovian rate constant only in the expressions derived earlier. Thus, just as in the reaction A + A →C and the reaction A + B →C neglecting force and initial correlations, the Modified Encounter Theory (MET), when reduced to equations of a Regular Form, both extends the time applicability range of ET homogeneous rate equation, and yields the inhomogeneous equation of the Generalized Encounter Theory (GET). It reveals macroscopic correlations induced by the encounters in the reservoir of free walks in full agreement with physical considerations. Time accumulation of macroscopic correlations obeys the same time law as in the previously considered case neglecting force interactions. Just the rate of the process will change, according to traditional redefinition of the steady-state constant of the reaction.     

Computer models of eutectic-type <Emphasis Type="Italic">T</Emphasis>–<Emphasis Type="Italic">x</Emphasis>–<Emphasis Type="Italic">y</Emphasis> diagrams with allotropy

Using the eutectic-type T–x–y diagram as an example, it can be represented the analysis of its geometrical construction dependence on the temperature of a component two polymorphous modifications which participate in mono- and invariant metatectic and invariant eutectic (eutectoid) transformations above or below (and within) binary eutectics temperature intervals and below a ternary eutectic temperature. Computer models for considered phase diagrams have been designed. Such models help to solve applied tasks like visualization, isopleths and isothermal sections decoding, mass balances calculation and evaluation of phase and conglomerate concentration in microstructure.     

Three New <Emphasis Type="Italic">in situ</Emphasis> Syntheses of <Emphasis Type="Italic">N</Emphasis>-Acyl-α-triphenylphosphonioglycinates

Summary. N-Acyl--hydroxyglycinates were transformed into N-acyl--triphenylphosphonioglycinates by (i) phosphorylation with Ph ₃PBr₂ in the presence of Et ₃N or (ii) in reaction with DCC and Ph ₃P·HBF₄ in the presence of catalytic amounts of Ph ₃P as well as (iii) by a new kind of Mitsunobu reaction with Ph ₃P·HBF₄ as a nucleophile conjugated acid. The N-acyl--triphenylphosphonioglycinates can be effectively used without isolation for a nucleophilic displacement of the triphenylphosphonium group to obtain corresponding -substituted -amino acid derivatives.     

Thermophysical properties of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimеthylacetamide mixtures with <Emphasis Type="Italic">n</Emphasis>-butanol

The refraction, dielectric, viscosity, density, data of the binary mixtures of N,N-dimethylacetamide (DMA) with n-butanol at 308.15 and 313.15 K. The measured parameters used to obtain derived properties like Bruggeman factor, molar refraction and excess static dielectric constant, excess inverse relaxation time, excess molar volume and excess viscosity, excess molar refraction. The variation in magnitude with composition and temperature of these quantities has been used to discuss the type, strength and nature of binary interactions. Results confirm that there are strong hydrogen-bond interactions between unlike molecules of DMA+ n-butanol mixtures and that 1: 1 complexes are formed and strength of intermolecular interaction increases with temperature.     

Simulated Microgravity Affects Growth of <Emphasis Type="Italic">Escherichia coli</Emphasis> and Recombinant β-<Emphasis Type="SmallCaps">d</Emphasis>-Glucuronidase Production

Effects of simulated microgravity (SMG) on bacteria have been studied in various aspects. However, few reports are available about production of recombinant protein expressed by bacteria in SMG. In this study growth of E. coli BL21 (DE3) cells transformed with pET-28a (+)-pgus in double-axis clinostat that could model low shear SMG environment and the recombinant β-d-glucuronidase (PGUS) expression have been investigated. Results showed that the cell dry weights in SMG were 16.47%, 38.06%, and 28.79% more than normal gravity (NG) control, and the efficiency of the recombinant PGUS expression in SMG were 18.33%, 19.36%, and 33.42% higher than that in NG at 19 °C, 28 °C, and 37 °C, respectively (P < 0.05).     

Study of<Emphasis Type="Italic"> β</Emphasis>–<Emphasis Type="Italic">α</Emphasis> recrystallization of the polypropylene

The crystalline modifications and of polypropylene (PP) were studied by using polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Typically crystals surrounded by spherulites were observed at low temperature. With increasing temperature the crystals melted and a new crystal appeared. More interestingly, the melting temperature of the new crystal was about 5 ° higher than that of spherulites originally present in the sample formed isothermally. It was assumed that this new crystal was the recrystalline crystal. This assumption was supported by the DSC results. Furthermore, the crystallization kinetics of the PP used was studied on the basis of the traditional Avrami analysis. As a result, the Avrami exponents of crystallization temperature from 120 to 130 °C ranged between 4.21 and 3.60, indicating that the crystallization mechanism of PP order melt was spherulitic growth and random nucleation.     

Synthesis of <Emphasis Type="Italic">α</Emphasis>-chloropyridine-containing oximes of 3<Emphasis Type="Italic">β</Emphasis>,5-dihydroxy-6-ketosteroids

New derivatives of steroidal 6-ketoximes containing α-chloropyridine neonicotinoid groups characteristic of bioactive compounds were synthesized by formation of oximes of cholestane and stigmastane 3β,5-dihydroxy-6-ketosteroids with O-(2-chloropyridin-5-ylmethyl)hydroxylamine in the presence of zinc or tin(IV) chloride.