Influence of Annealing on the Structural, Morphological, Photoluminescence and Visible Absorption Properties of Mg Doped CuO Micro Grains.

Narrow band gap oxide materials that harvest visible light have gained considerable attention for numerous visible light mediated applications. In this current work, a typical Mg doped CuO bulk material was prepared by a simple wet chemical method. The prepared material was annealed in three different temperatures viz.; 300 °C, 400 and 500 °C in air atmosphere to tune the optical band gap. XRD studies reveal that the average crystallite size increases with increase in annealing temperature. FESEM images of all the samples show their bulk nature with different grain sizes and morphologies. XPS survey scan spectra exhibit photoelectron emissions of Cu2p, O1s and Mg 1s with binding energies 933.69 eV, 533.41 eV and 1304.2 eV for all the samples and validated the effective incorporation of Mg ions into the CuO lattice. PL spectra reveal the polychromatic UV- visible luminescence bands for all the annealed samples, whereby the PL intensity is found to be decreasing as the annealing temperature increases. Finally, the band gap decreases with annealing temperature and indicates that the sample annealed at 500 °C can be exploited for visible light assisted applications such as solar cells, photocatalysis and photoelectrochemical cell.

In Staphylococcus aureus the regulation of pyruvate kinase activity by serine/threonine protein kinase favors biofilm formation.

Staphylococcus aureus, a natural inhabitant of nasopharyngeal tract, survives mainly as biofilms. Previously we have observed that S. aureus ATCC 12600 grown under anaerobic conditions exhibited high rate of biofilm formation and L-lactate dehydrogenase activity. Thus, the concentration of pyruvate plays a critical role in S. aureus, which is primarily catalyzed by pyruvate kinase (PK). Analyses of the PK gene sequence (JN645815) revealed presence of PknB site in PK gene indicating that phosphorylation may be influencing the functioning of PK. To establish this hypothesis the pure enzymes of S. aureus ATCC 12600 were obtained by expressing these genes in PK 1 and PV 1 (JN695616) clones and passing the cytosolic fractions through nickel metal chelate column. The molecular weights of pure recombinant PK and PknB are 63 and 73 kDa, respectively. The enzyme kinetics of pure PK showed K M of 0.69 ± 0.02 µM, while the K M of PknB for stpks (stpks = NLCNIPCSALLSSDITASVNCAK) substrate was 0.720 ± 0.08 mM and 0.380 ± 0.07 mM for autophosphorylation. The phosphorylated PK exhibited 40 % reduced activity (PK = 0.2 ± 0.015 µM NADH/min/ml to P-PK = 0.12 ± 0.01 µM NADH/min/ml). Elevated synthesis of pyruvate kinase was observed in S. aureus ATCC 12600 grown in anaerobic conditions suggesting that the formed pyruvate is more utilized in the synthesis phase, supporting increased rate of biofilm formation.

Copper catalyzed oxidative coupling of amines with formamides: a new approach for the synthesis of unsymmetrical urea derivatives.

Direct access to unsymmetrical urea derivatives via copper catalysed C-H/N-H coupling of formamides with amines has been developed at room temperature. This protocol is also applied to the synthesis of chiral urea derivatives.

Cloning, expression and characterization of NADP-dependent isocitrate dehydrogenase from Staphylococcus aureus.

The Krebs cycle dictates oxidative and reductive conditions in Staphylococcus aureus and is mainly regulated by isocitrate dehydrogenase (IDH) which plays pivotal role in the growth and pathogenesis of the bacteria. In the present study, IDH gene from S. aureus ATCC12600 was cloned in the Sma I site of pQE 30 vector; the resultant clone was named as UVIDH1. The insert in the clone was sequenced (accession number HM067707), and the sequence showed complete homology with IDH sequence of other S. aureus strains reported in the database indicating presence of single enzyme in S. aureus, and considerable sequence homology with other bacteria was observed; however, only 24% homology was found with NADP-dependent human IDH. Phylogenetically, the S. aureus IDH showed close identity with Bacillus subtilis and high degree of variability with other bacteria and human IDH. The expression of IDH in the clone UVIDH1 was induced with 1 mM IPTG, and the recombinant IDH was purified by passing through nickel metal chelate column; the purified recombinant IDH showed a single band in SDS-PAGE with a molecular weight of 40 kDa; K(m) and V(max) for isocitrate are 8.2 ± 0.28 and 525 ± 25 µM NADPH/mg/min, respectively, and for cofactor NADP 67.5 ± 2.82 µM and V(max) 50.5 ± 2.12 µM NADPH/mg/min.

Isocyanate- and isothiocyanate-derived Ru(IV)-based alkylidenes: synthesis, structure, and activity.

The synthesis and characterization of a series of isocyanate- and isothiocyanate-derived second generation Grubbs-Hoveyda-type ruthenium-alkylidene complexes, that is, [Ru(N=C=O)(2)(IMesH(2))(=CH-2-(2-PrO)-C(6)H(4))] (1), [Ru(N=C=O)(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(=CH-2-(2-PrO)-C(6)H(4))] (2), [Ru(N=C=S)(2)(IMesH(2))(=CH-2-(2-PrO)-C(6)H(4))] (3), and [Ru(N=C=S)(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(=CH-2-(2-PrO)-C(6)H(4))] (4), and their activity in various metathesis reactions are described. Compounds 1-4 were prepared by reaction of the parent complexes [RuCl(2)(IMesH(2))(=CH-2-(2-PrO)C(6)H(4))] (5) (IMesH(2)=1,3-bis-(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) and [RuCl(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(=CH-2-(2-PrO)-C(6)H(4))] (6) with silver cyanate and thiocyanate, respectively. The X-ray structure of 1 was determined, confirming the isocyanate-type bonding of the ligand. The isothiocyanate-type bonding in 3 and 4 was unambiguously confirmed by IR and (13)C NMR spectroscopy. The isocyanate-derived complexes 1 and 2 were found to be excellent catalysts for the ring-opening metathesis polymerization (ROMP) of cis-cycloocta-1,5-diene (COD). Both 1 and 2 yielded poly(COD) with a trans-content of about 80 %. First-order kinetics with unprecedentedly high rate constants of polymerization (k(p)=0.068 and 0.26 s(-1), respectively) were observed. Compounds 3 and 4 were also active initiators for the ROMP of COD, however, they generated poly(COD) with a cis-content of 80 and 67 %, respectively. Complexes 1 and 2 also showed good catalytic activity in cross-metathesis (CM) reactions. Finally, 1-4 were also found to be excellent catalysts for the regioselective cyclopolymerization of diethyl 2,2-dipropargylmalonate (DEDPM), resulting in poly(DEDPM) almost entirely based on five-membered repeat units, that is, cyclopent-1-ene-1,2-vinylenes.

Factors relevant for the regioselective cyclopolymerization of 1,6-heptadiynes, N,N-dipropargylamines, N,N-dipropargylammonium salts, and dipropargyl ethers by Ru(IV)-alkylidene-based metathesis initiators.

The factors relevant for the regioselectivity of insertion of various 1,6-heptadiynes, N,N-dipropargylamines, N,N-dipropargylammonium salts and dipropargyl ethers into different Ru(IV)-alkylidenes, i.e., [Ru(CF(3)COO)(2)(IMesH(2))(CHR), (R = 2,4,5-(MeO)(3)-C(6)H(2) (I1), 2-(2-PrO)-5-NO(2)-C(6)H(3) (I3), 2-(2-PrO)-C(6)H(4) (I4)), [Ru(CF(3)COO)(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO(2)-C(6)H(3))] (I2), [Ru(CF(3)COO)(2)(3-mesityl-1-((1'R)-1'-phenylethyl)-imidazolin-2-ylidene)(CH-2-(2-PrO)C(6)H(4))] (I5) and [Ru(C(6)F(5)COO)(2)(IMesH(2))(CH-2-(2-PrO)-C(6)H(4))] (I6), (IMesH(2) = 1,3-dimesitylimidazolin-2-ylidene), is described. (13)C NMR experiments revealed that all polymers synthesized by the action of I1-I6 consisted virtually solely (>95%) of five-membered repeat units, i.e., (cyclopent-1-enylene)-1,2-vinylenes, 3,4-(1H-2,5-dihydropyrrylenium)-3,4-vinylenes, and (2-pentyl-2,5-dihydrofurylene)-3,4-vinylenes, respectively. The (13)C NMR-based assignments were supported by the synthesis of model compounds, i.e., (cyclopent-3-ene-1,1-diyldimethylbis(tris(3,5-dimethoxyphenyl)carboxylate) (MC1) and N-propyl-N-ethyl-2,5-dihydropyrrolium tetrafluoroborate (MC2), as well as by ene-yne cross metathesis reactions of 3-(propargyloxy)-1-octyne (M6) with trimethylallylsilane. In the polymerization of N-ethyl-N,N-dipropargylamine (M9), an intermediate was isolated that sheds light onto the role of heteroatoms in the 4-position of 1,6-heptadiynes in cyclopolymerization. In addition, in the cyclopolymerization of M9 by I4 the product resulting from back-biting has been isolated and explains for the low polymerization propensity of Ru-alkylidenes for N-alkyl-N,N-dipropargylamines.