Preparation,characterization and morphological study of poly(<Emphasis Type="Italic">m</Emphasis>-toluidine-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-aminoacetophenone) conductive copolymer

A new series of copolymers of poly(m-toluidine-co-m-aminoacetophenone) were synthesized by the chemical oxidative method in acid medium. The copolymers were characterized by UV–Vis and FTIR spectroscopy. X-ray diffraction analysis revealed the partial crystalline nature of copolymer. The morphological study by SEM analysis indicated that the surface of the copolymer had the granular structure of agglomerated morphology with average particle size of 200 nm. The conductivity of the copolymers ranged from 2 × 10^–4 to 3.3 × 10^–8 S/cm and the conductivity decreased with the increase of comonomer concentration. The resultant copolymers showed an enhanced solubility and an improved processability when compared with pure polyaniline.     

Conducting materials prepared by the oxidation of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-benzoquinone

p-Phenylenediamine was oxidized with p-benzoquinone in the aqueous solutions of methanesulfonic acid (MSA). The conductivity of the products increased with increasing concentration of MSA from 1.5?×?10^?12 S cm^?1 in 0.1 M MSA up to 3.4?×?10^?4 S cm^?1 in 5 M MSA. The low-molecular-weight products are basically composed of one p-benzoquinone and two p-phenylenediamine molecules. Their molecular structure is discussed on the basis of mass, Fourier-transform infrared, Raman, NMR and electron paramagnetic resonance (EPR) spectroscopies. The formation of 2,5-di(p-phenylenediamine)-p-benzoquinone protonated with methanesulfonic acid best complies with the information provided by spectroscopic techniques. Its conversion to hydroquinone tautomer explains the formation of unpaired spins observed by EPR and their potential contribution to the conduction.     

Stability of <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-element diphosphates in water

The mean atomic Gibbs energies of formation of (Δ _f ? _at ⁰ ) of s-, p-, and d-element diphosphates have been calculated using ion increments of the Gibbs energy (Δ _f G ⁰). The diphosphate hydrolysis kinetics is considered, and a correlation between the Δ _f ? _at ⁰ values and the hydrolysis rate constants is presented.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

RAFT polymerization of linear ABC triblock copolymer P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS-<Emphasis Type="Italic">b</Emphasis>-P2VP and regulation of its hierarchical self-assembly structure in solution

Linear ABC triblock copolymer PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ was successfully synthesized by RAFT polymerization. Block copolymer micelles were prepared by the two-step hierarchical self-assembly process. Size exclusion chromatography and ¹H NMR were used to characterize the structure of samples. Morphologies and size of micelles were determined by transmission electron microscope. The results showed that the densely dispersed spherical micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were obtained in the first step of the hierarchical self-assembly process. In the second step, core-compartmentalized micelle strings with different lengths and distribution densities were obtained when the primary self-assembled solution was dialyzed in distilled water with pH ≈ 3. When distilled water with pH ≈ 3 was added drop-wise to this solution, uniformly dispersed spherical core-compartmentalized micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were prepared. Thus, hierarchical self-assembly structure of linear ABC triblock copolymer was obtained successfully and the preparation of uniformly dispersed spherical micelles of triblock copolymers was realized simply by changing the secondary self-assembly methods.     

Binuclear copper(II) complexes with acyldihydrazones of <Emphasis Type="Italic">N</Emphasis>-benzenesulfonyl-<Emphasis Type="Italic">L</Emphasis>-aspartic acid

The structure and the EPR spectra of copper(II) coordination compounds with acyldihydrazones of N-benzenesulfonyl-L-aspartic acid and salicylaldehyde (2-hydroxyacetophenone) were described. The compounds were studied by chemical and thermal analyses, IR spectroscopy, and EPR. The molecular and crystal structures of copper(II) complexes with N-benzenesulfonyl-L-aspartic acid bis(salicylidene)hydrazone (H₄L¹) [Cu₂L¹ · 2Py] · 1.5 H₂O was determined by X-ray diffraction. The crystals are triclinic: a = 10.4714(4) Å, b = 12.9702(5) Å, c = 14.6187(9) Å, α = 104.763(2)°, β = 93.082(2)°, γ = 111.4240(10)°, space group P \(\bar 1\), Z = 2. The binuclear complexes containing copper cations whose coordination polyhedra are connected by an aliphatic spacer (Cu...Cu, 8.669 Å) are additionally linked by phenoxy bridges (Cu...Cu, 3.398 Å). The EPR spectra of these compounds in solutions exhibit an isotropic signal of seven HFS lines due to two equivalent copper ions with the spin Hamiltonian parameters g = 2.115?2.120, a _Cu = (35.5?38.0) × 10^?4 cm^?1, which is indicative of weak exchange interactions between the paramagnetic sites.     

Characterization of Truncated <Emphasis Type="Italic">dsz</Emphasis> Operon Responsible for Dibenzothiophene Biodesulfurization in <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. FUM94

Numerous desulfurizing bacteria from the Rhodococcus genus harbor conserved dsz genes responsible for the degradation of sulfur compounds through 4S pathway. This study describes a newly identified desulfurizing bacterium, Rhodococcus sp. FUM94, which unlike previously identified strains encodes a truncated dsz operon. DNA sequencing revealed a frameshift mutation in the dszA gene, which led to an alteration of 66 amino acids and deletion of other C-terminal 66 amino acids. The resulting DszA polypeptide was shorter than DszA in Rhodococcus sp. IGTS8 reference strain. Despite the truncation, desulfurizing activity of the operon was observed and attributed to the removal of an overlap of dszA and dszB genes, and lack of active site in the altered region. Desulfurization experiments resulted in specific production rate of 6.3 mmol 2-hydroxy biphenyl (kgDCW)^?1 h^?1 at 2 g l^?1 biocatalyst concentration and 68.8% biodesulfurization yield at 20 g l^?1 biocatalyst concentration, both at 271 μM dibenzothiophene concentration which is comparable to similar wild-type biocatalysts.     

Synthesis and crystal structure of <Emphasis Type="Italic">N,N</Emphasis>-dimethylbiguanidinium hexafluorosilicate

The complex [(CH₃)₂NC(NH₂)NHC(NH₂)NH₂]SiF₆ (I) was synthesized and its structure was determined by X-ray crystallography. The crystals are monoclinic: a = 7.4346(10) Å, b = 12.7628(10) Å, c = 11.0828(10) Å, β 104.080(10)°, V = 1020.01(18) ų, ρ_calc = 1.780 g/cm³, μ(MoK _α) = 0.302 mm^?1, Z = 4, space group P2₁/c. The crystals of I are composed of SiF ₆ ^2? anions (Si-F, 1.657(2)–1.699(2) Å) and N,N-dimethylbiguanidinium (H₂L²⁺) cations combined in a framework by interionic H-bonds NH···F. In the cations, protonation sites are the terminal imide groups.     

Production of <Emphasis Type="Italic">R</Emphasis>-Mandelic Acid Using Nitrilase from Recombinant <Emphasis Type="Italic">E. coli</Emphasis> Cells Immobilized with Tris(Hydroxymethyl)Phosphine

Recombinant Escherichia coli cells harboring nitrilase from Alcaligenes faecalis were immobilized using tris(hydroxymethyl)phosphine (THP) as the coupling agent. The optimal pH and temperature of the THP-immobilized cells were determined at pH 8.0 and 55 °C. The half-lives of THP-immobilized cells measured at 35, 40, and 50 °C were 1800, 965, and 163 h, respectively. The concentration of R-mandelic acid (R-MA) reached 358 mM after merely 1-h conversion by the immobilized cells with 500 mM R,S-mandelonitrile (R,S-MN), affording the highest productivity of 1307 g L^?1 day^?1 and the space-time productivity of 143.2 mmol L^?1 h^?1 g^?1. The immobilized cells with granular shape were successfully recycled for 60 batches using 100 mM R,S-MN as substrate at 40 °C with 64% of relative activity, suggesting that the immobilized E. coli cells obtained in this study are promising for the production of R-MA.     

Ultrasound-assisted synthesis of block copolymers of chitosan and <Emphasis Type="Italic">D</Emphasis>,<Emphasis Type="Italic">L</Emphasis>-lactide: Structure and properties

The block copolymers of chitosan with D,L-lactide are synthesized under UV irradiation of the homogeneous solution of the corresponding homopolymers with the yield of the main product being 96 wt %. The polyblock structure of copolymer chains, in which the size of polylactide blocks is varied in the range of (2.9–22.0) × 10³ depending on the synthesis conditions, is demonstrated. The incorporation of polylactide blocks into the structure of chitosan leads to development of the material structure close to the structure of polylactide. The films of the block copolymers containing 16 wt % polylactide and having a molecular mass of its blocks of 22.0 × 10³ have increased values of breaking stress (47 MPa) and ultimate strain (20%) compared to chitosan (24 MPa and 1.9%, respectively). The obtained block copolymers possess bactericidal properties.     

Mononuclear cobalt (III) complexes with <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-bromobenzylamine and <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-chlorobenzylamine

Cobalt (III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H₂sbba) and N-salicylidene-2-hydroxy-5-chlorobenzylamine (H₂scba), [n-(C₄H₉)₄N][Co(sbba)₂] (I) and [n-(C₄H₉)₄N][Co(scba)₂] (II), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P2₁/n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4)°, V = 4208.2(14) ų, D_x = 1.295 g cm^?3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra(n-butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba^2? ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N₂O₄ donor set.     

Secondary self-assembly behaviors of PEO-<Emphasis Type="Italic">b</Emphasis>-P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS triblock terpolymers in solution

A series of PEO₄₅-b-PtBA₅₃-b-PS _x (x = 42, 84, 165) triblock terpolymers were synthesized by the atom transfer radical polymerization and characterized by size exclusion chromatography and ¹H NMR. Their self-assemblies were conducted by a two-step hierarchical self-assembly method and a one-step dialysis method and the self-assembly behaviors were investigated. The morphologies, sizes, and size distributions of micelles produced by the self-assembly were determined by transmission electron microscopy and dynamic light scattering. The secondary self-assembled structure of PEO₄₅-b-PtBA₅₃-b-PS _x obtained by the two-step hierarchical self-assembly could be controlled by tuning the length of PS block, the core forming block. The micelles were uniform with diameters of 20–25 nm and their size distributions, except for that of PEO₄₅-b-PtBA₅₃-b-PS₁₆₅, were narrow with particle size distribution indexes ranging from 0.014 to 0.246. The one-step dialysis of the triblock terpolymers produced vesicular micelles with distinct vesicle walls that exhibited similar thicknesses. The vesicles did not show significant aggregation. The size distribution of PEO₄₅-b-PtBA₅₃-b-PS₄₂ vesicle was the narrowest with a particle size distribution index value of 0.135. The PEO₄₅-b-PtBA₅₃-b-PS₁₆₅ vesicles tended to overlap with each other.     

Kinetics of Na|CF<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> and Li|CF<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> systems

Properties of CF _x /Li and CF _x /Na cells were examined while using galvanostatic charging/discharging, electrochemical impedance spectroscopy and scanning electron microscopy (SEM). The capacity during the first cycle was as high as ca. 1000 mAh g^?1. Such an electrode is suitable for primary CF _x /Li and CF _x /Na batteries. SEM images of CF _x cathode showed that during discharging it was transformed into amorphous carbon and LiF or NaF crystals (of diameter of ca. 5–20 μm). These systems (C?+?LiF or C?+?NaF) cannot be reversibly converted back into CF _x /Li or CF _x /Na, respectively. Exchange current densities are between 10^?7 Acm^?2 and 10^?9 Acm^?2 when working with LiPF₆ and NaPF₆ electrolytes (1.12?×?10^?7 Acm^?2 and 6.82?×?10^?9 Acm^?2, respectively). Those values are low and indicate that the charge transfer process may be the rate-determining step. Activation energies for the charge transfer process were 57 and 72 kJ mol^?1 for CF _x /LiPF₆ and CF _x /NaPF₆ systems, respectively. Higher activation energy barrier for the CF/Na⁺?+?e^??→?C?+?NaF reaction results in lower observed exchange current density in comparison to the system with lithium ions.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.     

<Emphasis Type="Italic">Stachys lavandulifolia</Emphasis> and <Emphasis Type="Italic">Lathyrus</Emphasis> sp. Mediated for Green Synthesis of Silver Nanoparticles and Evaluation Its Antifungal Activity Against <Emphasis Type="Italic">Dothiorella sarmentorum</Emphasis>

In this study, silver nanoparticles (AgNPs) were biosynthesized using Stachys lavandulifolia and Lathyrus sp. The first sign of the reduction of silver ions to AgNPs was the change in color of S. lavandulifolia and Lathyrus sp. extracts changed into dark brown and auburn after treating with silver nitrate, respectively. The UV–Vis spectroscopy of reaction mixture (extract+silver nitrate) produced by S. lavandulifolia and Lathyrus sp. showed the strong adsorption peaks at ?440 and 420 nm, respectively. The transmission electron microscope images showed the synthesis of AgNPs using S. lavandulifolia and Lathyrus sp. with an average size of 7 and 11 nm, respectively. The result of X-ray diffraction pattern showed four diffraction peaks at 38°, 44°, 64°, and 77° for both types of biosynthesized AgNPs. Fourier transform infrared spectroscopy showed the possible role of involved proteins and polyhydroxyl functional groups in the synthesis process of AgNPs. Inductively coupled plasma analysis determined the conversion rate (percentage) of silver ions to silver nanoparticles in reaction mixtures of S. lavandulifolia and Lathyrus sp. 99.73 and 99.67 %, respectively. In addition, antifungal effect of AgNPs, synthesized by both extracts, was studied separately on mycelial growth of Dothiorella sarmentorum, in a completely randomized design on potato dextrose agar (PDA) medium. The inhibition rate of mycelial growth was strongly depended on the density of AgNPs and it strongly increased with increasing the density of AgNPs in the PDA medium. AgNPs more than 90 % of them inhibited from the mycelia growth of the fungus at the concentration of 40 µg/mL and higher.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-and <Emphasis Type="Italic">C</Emphasis>-trimethylsilyl-substituded anililes

N-Metallation of bromoanilines with ethylmagnesium bromide followed by a reaction with trimethylchlorosilane provided N-mono and N-bis(trimethylsilyl)bromoanilines depending on the structure of substrate. The metallation of bissilylated bromoanilines with butyllithium permitted the introduction of a trimethylsilyl substituent in the aromatic ring. Previously unknown 2-bromo-N,N-bis(trimethylsilyl)aniline, 2,6-dibromo-N-trimethylsilylaniline, 2,6-dibromo-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilylaniline, 2-bromo-6-trimethylsilyl-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilyl-N-trimethylsilylaniline, 2,4,6-tribromo-N-trimethylsilylaniline, and 2,4,6-tribromo-N,N-bis(trimethylsilyl)aniline were prepared. The structures of the compounds obtained were established by the chromato-mass spectrometry and ¹H, ¹³C, and ²⁹Si NMR spectroscopy.     

Features of self-organization of highly dilute solutions of (<Emphasis Type="Italic">S</Emphasis>)-, (<Emphasis Type="Italic">R</Emphasis>)-, and (<Emphasis Type="Italic">SR</Emphasis>)-methionines and related carbamides and glycolurils

Aqueous solutions of (S)-, (R)-, and (SR)-methionines (1–3); carbamide (4); (S)-, (R)-, and (SR)-N-carbamoylmethionines (5–7); glycoluril (8); and glycolurils containing (S)and (R)-methionine moieties (9 and 10) kept under natural and hypoelectromagnetic conditions were studied in comparison by a complex of physicochemical methods (dynamic and electrophoretic light scattering, conductometry, pH-metry, and dielcometry). The process of selforganization and the properties of dilute solutions (1.0?10^–15–10^–1 mol L^–1) of compounds 1–10 was shown for the first time to depend substantially on the structure of the solute and configuration of methionine (Met) enantiomers. In the series 1–3, the greatest ability to self-organization is observed for solutions of (SR)-Met in which supramolecular domains (1.0?10^–5–1.0?10^–1 mol L^–1) and nanoassociates (1.0?10^–11–1.0?10^–8 mol L^–1) are formed. The formation of nanoassociates in a concentration range of 1.0?10^–12–1.0?10^–6 mol L^–1 can be responsible for the appearance of nonmonotonic concentration dependences of the physicochemical properties of solutions of N-carbamoylmethionines 5–7, whereas the physicochemical properties are more pronounced in solution of (S)-N-carbamoylmethionine 5 than in solutions of 6 and 7. The strongest influence of the configuration of the Met enantiomer on the ability of solution to self-organization was revealed in a series of glycolurils 9, 10: solutions of 9 with the (S)-Met moiety are disperse systems in which nanoassociates are formed in a range of 1.0?10^–15–1.0?10^–5 mol L^–1, whereas in solutions of 10 with the (R)-Met fragment the ability to self-organization in the low-concentration range is absent.     

Viscosities and Surface Tensions of Phenetole with <Emphasis Type="Italic">N</Emphasis>-Methyl-2-pyrrolidone, <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide and Tetrahydrofuran Binary Systems at Three Temperatures

Viscosities, η, and surface tensions, σ, of binary systems of phenetole (ethoxy benzene or ethyl phenyl ether) with N-methyl-2-pyrrolidone, N,N-dimethylformamide or with tetrahydrofuran were measured over the entire mole fraction range and at (298, 303 and 308) K. The experimental data was used to compute the deviations in viscosity, Δη, and surface tension, Δσ. Values of the excess Gibbs energy of activation G*^E, surface entropy S _σ and surface enthalpy H _σ were calculated. Viscosity data of the binary systems were calculated using the Grunberg and Nissan and the three-body and four-body McAllister correlations. The Redlich–Kister method was used for evaluation of coefficients and standard deviations for Δη, Δσ and G*^E. The results were interpreted in terms of the probable effect of molecular interactions between components as well as polarity.     

Study of the growth of <Emphasis Type="Italic">Enterococcus faecalis</Emphasis>, <Emphasis Type="Italic">Escherichia coli</Emphasis> and their mixtures by microcalorimetry

In a majority of environments, microbes live as interacting communities. Microbial communities are composed of a mix of microbes with often unknown functions. Polymicrobial diseases represent the clinical and pathological manifestations induced by the presence of multiple infectious agents. These diseases are difficult to diagnose and treat and usually are more severe than monomicrobial infections. The interaction relationship between Enterococcus faecalis and Escherichia coli was researched using a Calvet calorimeter. Three mixtures of both bacteria were prepared in the following proportions: 20 + 80 % (0.2 mL E. faecalis + 0.8 mL E. coli), 50 + 50 % (0.5 mL E. faecalis + 0.5 mL E. coli) and 80 + 20 % (0.8 mL E. faecalis + 0.2 mL E. coli). Experiments were carried out at concentration of 10⁶ CFU mL^?1 and a constant temperature of 309.65 K. The differences in shape of graph of E. faecalis, E. coli and their mixtures were compared. Also, the thermokinetic parameters such as detection time (t _d), growth constant (k), generation time (G) and the amount of heat released (Q) were calculated.     

Electronic Structure and Relative Stabilities of 10- and 12-Vertex. <Emphasis Type="Italic">Closo</Emphasis>and <Emphasis Type="Italic">Nido</Emphasis>-Heteroborane Clusters of Ga,Ge, and As Elements

A DFT method with the B3LYP functional and the 6-311++G(d,p) diffuse basis set is used to predict geometries, relative stabilities, electronic structures, and the bonding of closo- and nido-Ga_mB_n–mH _n ^2? , Ge_mB_n–mH _n ^m?2 , and As_mB_n–mH _n ^{2 m?2} (n = 10, 12 and m = 1, 2) Clusters are obtained by replacing BH with isolobal GaH, GeH⁺, and AsH²⁺ fragments, keeping the same skeleton electron pairs (SEP). Based on the polyhedral skeletal electron pairs theory (PSEPT), closo and nido structures are predicted and can be of significant interest for experimentalists working in the field of heteroboranes. Different cluster stabilities are studied according to Gimarc′s and Williams′ rules, where our calculations show that the monosubstituted clusters deviate from these rules, giving rise to open structures. As₂B₈H _n ²⁺ as 10-vertex structures lead to nido-type clusters, however, Ge_mB_n–mH _n ^m?2 (n = 10, 12 and m = 1, 2) give rise to closo isomers with close energies. All optimized structures exhibit large HOMO–LUMO gaps suggesting a good kinetic stability, thus predicting their isolation and characterization.