2-[(3,5-Diphenyl-1H-pyrazol-1-yl)meth­yl]pyridine

The title compound, C21H17N3, crystallizes with the phenyl ring in the 3-position coplanar with the pyrazole ring within 4.04 (5)°, whereas the phenyl ring in the 5-position forms a dihedral angle of 50.22 (3)° with the pyrazole ring. There is no ambiguity regarding the position of pyridine N atom, which could have exhibited disorder between the ortho positions of the ring

Ring-Opening Polymerization of Lactides by (Pyrazol-1-ylmethyl)pyridine Zn(II) and Cu(II) Complexes: Kinetics, Mechanism and Tacticity Studies

The kinetics, mechanism and polymer microstructure studies of ring-opening polymerization (ROP) of lactides (LA) by Zn(II) and Cu(II) complexes of (pyrazolylmethyl)pyridine ligands, 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2) is described. The complexes [Zn(Ac)2(L1)] (1), [Cu(Ac)2(L1)] (2), [Zn(Ac)2(L2)] (3) and [Cu2(Ac)4(L2)2] (4) formactive initiators in the ROP of D,L-LA and L-LA monomers. Generally Zn(II) complexes 1 and 3 exhibit higher activities compared to the corresponding Cu(II) complexes 2 and 4. Polymerization kinetics of D,L-LA show higher rates compared to the L-LA reactions. All the polymerization reactions follow pseudo first-order kinetics with respect to monomer while 1 shows second-order dependency on the polymerization reactions. Molecular weights of the polymers range from 813 g mol–1 to 9207 g mol–1 and exhibit relatively narrow molecular weight distributions between 1.2 to 1.6. While poly(D,L-LA) are predominantly atactic, poly(L-LA) are largely isotactic. All polymerization reactions proceed through coordination insertion mechanism followed by hydrolysis of the end groups.KEYWORDS Zinc and copper complexes, lactide, polymerization, kinetics, mechanism.PDF and Supp files attache

Synthesis, detection and quantification of inulooligosaccharides and fructooligosaccharides by extracellular and intracellular inulinase and fructosyltransferase enzymes isolated from coprophilous fungi.

Masters Degree. University of KwaZulu-Natal, Durban.Exploration of fungal biodiversity capable of producing fructosyltransferase and inulinase enzymes in significant amounts is crucial for the production of oligofructans. Indigenous coprophilous fungi are predominantly sustainable bioresources, harbouring novel enzymes with potential industrial and biotechnological applications. Fructosyltransferase (Ftase) and inulinase are gaining considerable attention due to their capability to synthesise biofunctional nutraceuticals with low calories and health benefits when ingested in recommended dosages. Hence, due to several health benefits associated with prebiotics, bioprospecting for coprophilous fungi as unique bioresources of fructosyltransferase and inulinase was imperative. The present study therefore focused on the collection of herbivore dung from various terrestrial habitats in KwaZulu-Natal Province, South Africa whereby sixty-one (61) indigenous coprophilous fungal strains were isolated after repeated purification to monoculture. The axenic fungal strains were identified using morpho-taxonomic keys and molecular identification by 18S rDNA sequencing where Neocosmospora spp, Trichoderma spp., Aspergillus spp and Fusarium spp. were dominant. The fungal strains were subsequently assessed for their ability to produce extracellular and intracellular Ftase and inulinase enzymes. During the preliminary screening, the culture filtrate was examined for transfructosylating and hydrolytic activity using 2,3,5-triphenyl tetrazolium chloride (TTC) as a chromogenic marker and Lugol’s iodine solution, respectively. Zones of hydrolysis on 30 fungal isolates were observed on the TTC assay plates in diameters ranging from 15 mm to 30 mm, representing high extracellular Ftase activity. The formation of clear zones following addition of iodine solution on inulin rich media indicated the presence of inulinolytic activity. Secondary screening involved DNS assays of eight (8) isolates that secreted high concentrations of Ftase while six (6) different fungal strains showed <50 % inulinase: invertase ratio. The final screening step was tertiary screening where products of biocatalysis were qualitatively detected by thin layer chromatography to visualize saccharide spots of fructooligosaccharides and inulooligosaccharides. HPLC analysis of Ftase and inulinase reaction products revealed and further confirmed that coprophilous fungi harbour fructosyltransferase and inulinase enzymes. The crude extracellular fructosyltransferase enzyme was partially purified by 9.3-fold with a yield of 7.3 % and a specific activity of 2465.5 U mg-1 after a three-step procedure involving (NH4)2SO4 fractionation, dialysis and ion exchange chromatography. The apparent molecular weight of this Ftase was estimated by SDS-PAGE to be approximately 70 kDa. Zymogram analysis under non-reducing conditions showed the enzyme migrating as a polydisperse aggregate yielding broad band of approximately 100 kDa. The enzyme further exhibited an enhanced activity at a broad pH range of 4.0 – 8.0 and optimal activity at a temperature range of 40 °C – 80 °C, while the enzyme was stable at pH 8.0 and between 40 °C – 60 °C, respectively. Under these conditions, the enzyme remained stable retaining 95 % residual activity after incubation for 6 h. The presence of metal ions such as Hg2+ and Ag2+ inhibited Ftase activity while, Ca2+, Mg2+ and K+ at 1 mM increased the enzyme activity, with stabilization observed with Na+, Zn2+ and Cu2+. With sucrose as the substrate, the enzyme kinetics fitted the Michaelis-Menten model. The Km, Vmax and kcat values were 2.076 mM, 4.717 μmole min-1, and 4.7 min-1, respectively with a catalytic efficiency of 2.265 μmole min-1. In vitro antioxidant potential of FOS by 1,1 - diphenyl-2-picryl hydroxyl (DPPH) assay, ferric reducing antioxidant power (FRAP) assay and nitric oxide (NO) radical inhibition yielded IC50 of 6.71 μg/ml, 1.76 μg/ml and IC25 of 0.27 μg/ml, respectively. Free radical scavenging and inhibition activities showed a concentration-dependent antioxidant activity with no significant differences with oligosaccharide standards (p < 0.01). However, vitamin C was significant in FRAP and NO assays. These results clearly demonstrated that an indigenous coprophilous fungus is a potential new reservoir of salient biotechnological enzymes that can be exploited for the production of prebiotics for subsequent biotechnological applications

Ethyl 3-ferrocenyl-1-(pyridin-2-ylmeth­yl)-1H-pyrazole-5-carboxyl­ate

The title compound, [Fe(C5H5)(C17H16N3O2)], crystallizes with an essentially eclipsed conformation of the cyclo­penta­dienyl (Cp) rings. The unsubstituted ring is disordered over two positions with the major component being present 90 (1)% of the time. The substituted Cp ring, the pyrazole ring and three atoms of the eth­oxy­carbonyl group form a conjugated π-system. These 13 atoms are coplanar within 0.09 Å

[Bis(pyridin-2-ylmethyl) ether]- trichloridorhodium(III) dichloromethane monosolvate : unusual hydrolysis of the methylene bridge in (pyrazolylmethyl)- pyridine

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Mutations of mtDNA polymerase-γ and hyperlactataemia in the HIV-infected Zulu population of South Africa

Background. Mitochondrial toxicity, particularly symptomatic hyperlactataemia or lactic acidosis (SHL/LA), has been attributed to the use of nucleoside reverse transcriptase inhibitors (NRTIs), possibly because of their capacity to impede human mitochondrial DNA polymerase-γ (POLG), which is responsible for the replication of mitochondrial DNA.Objective. To determine whether known monogenic POLG1 polymorphisms could be linked with the unexpectedly high incidence of SHL/ LA observed in HIV-infected Zulu-speaking patients exposed to the NRTIs stavudine or zidovudine in their antiretroviral therapy.Methods. One hundred and sixteen patients from Edendale Hospital, Pietermaritzburg, South Africa, participated in the study between March and August 2014. Fifty-nine symptomatic cases were compared with 57 non-symptomatic controls on stavudine for ≥24 months. Among the symptomatic patients, 13 had SHL with measured lactate between 3.0 and 4.99 mmol/L, and 46 had LA with a lactate level ≥5 mmol/L. Genomic DNA from 113 samples was used for subsequent allelic discrimination polymerase chain reaction screening for the R964C and E1143G single-nucleotide polymorphisms of POLG1. Sequencing was performed for 40/113 randomly selected samples for confirmation of the genotyping results.Results. Neither of the two known POLG1 mutations was observed. The cases presented with SHL/LA between 4 and 18 months on stavudine. Females (70.4%) were significantly (p&lt;0.001) more likely to be cases (adjusted odds ratio 24.24, 95% CI 5.14 - 114.25) compared with males.Conclusion. This study has shown that our sample of the Zulu-speaking population does not exhibit a genetic predisposition to SHL/LA associated with known monogenic POLG1 mutations, indicating another possible predisposing factor for increased risk of SHL/LA

(Pyridyl)benzoazole ruthenium(III) complexes: Kinetics of ligand substitution reaction and potential cytotoxic properties

The present work investigates the kinetics of ligand substitution reaction and anticancer activities of the complexes, [{2-(2-pyridyl) benzimidazole} RuCl3] (C1), [{2-(2-pyridyl) benzoxazole} RuCl3] (C2), [{2-(2-pyridyl) benzothiazole} RuCl3] (C3) and [{1-propyl-2- (pyridin-2-yl)-H-benzoimidazole} RuCl3] (C4). The substitution kinetics reaction of the complexes with the three bio-relevant nucleophiles, viz.: thiourea (TU), 1, 3-dimethyl-2-thiourea (DMTU) and 1, 1, 3, 3-tetramethyl-2-thiourea (TMTU) was investigated under pseudo first-order conditions as a function of concentration and temperature using UV–Visible spectrophotometer. The substitution of the coordinated chloride was controlled by the electronic effect. The order of reactivity of the complexes with the nucleophiles is in the form C1 > C2 > C3 > C4 which is in line with the density functional theory (DFT) studies. The complexes showed minimal anticancer activity against the HeLa cell line, which is in contrast to the molecular docking experiments that exhibited stronger DNA binding affinities. © 2018 Elsevier B.V

trans-Dichloridobis(4-methoxy­aniline-κN)palladium(II)

In the title compound, [PdCl2(C7H9NO)2], the Pd atom is situated on a crystallographic centre of inversion. The coordination environment of the Pd atom shows a slightly distorted square-planar geometry. The crystal structure exhibits weak inter­molecular Pd⋯Cl inter­actions, with Pd⋯Cl distances of 3.6912 (6) Å. A chain-like arrangement of mol­ecules realized by inter­molecular N—H⋯Cl hydrogen bonds is observed along [010]

Dichlorido{2-[(thio­phen-2-ylmeth­yl)imino­meth­yl]pyridine-κ2 N,N′}palladium(II)

In the title compound, [PdCl2(C11H10N2S)], the PdII ion is four-coordinated in a distorted square-planar environment by two N atoms of the chelating 2-[(thio­phen-2-ylmeth­yl)imino­meth­yl]pyridine ligand and two chloride anions. The thio­phene ring is rotationally disordered over two orientations in a 1:1 ratio. The crystal packing exhibits weak inter­molecular C—H⋯Cl and C—H⋯S hydrogen bonds