Synthesis and Structural Elucidation of Triazolylmolybdenum(VI) Oxide Hybrids and Their Behavior as Oxidation Catalysts

A large family of bifunctional 1,2,4-triazole molecular tectons (tr) has been explored for engineering molybdenum(VI) oxide hybrid solids. Specifically, tr ligands bearing auxiliary basic or acidic groups were of the type amine, pyrazole, 1H-tetrazole, and 1,2,4-triazole. The organically templated molybdenum(VI) oxide solids with the general compositions [MoO3(tr)], [Mo2O6(tr)], and [Mo2O6(tr)(H2O)2] were prepared under mild hydrothermal conditions or by refluxing in water. Their crystal structures consist of zigzag chains, ribbons, or helixes of alternating cis-{MoO4N2} or {MoO5N} polyhedra stapled by short [N–N]-tr bridges that for bitriazole ligands convert the motifs into 2D or 3D frameworks. The high thermal (235–350 °C) and chemical stability observed for the materials makes them promising for catalytic applications. The molybdenum(VI) oxide hybrids were successfully explored as versatile oxidation catalysts with tert-butyl hydroperoxide (TBHP) or aqueous H2O2 as an oxygen source, at 70 °C. Catalytic performances were influenced by the different acidic–basic properties and steric hindrances of coordinating organic ligands as well as the structural dimensionality of the hybrid.

Publications.

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Synthesis and screening of potential antimicrobial compounds

Tuberculosis (TB), an infection caused by human pathogen Mycobacterium tuberculosis, continues to kill millions each year and is as prevalent as it was in the pre-antimicrobial era. With the emergence of continuously-evolving multi-drug resistant strains (MDR) and the implications of the HIV epidemic, it is crucial that new drugs with better efficacy and affordable cost are developed to treat TB. With this in mind, the first part of this thesis discusses the synthesis of libraries of derivatives of pyridine carboxamidrazones, along with cyclised (1,2,4-triazole and 1,2,4-oxadiazole) and fluorinated analogues. Microbiological screening against M. tuberculosis was carried out at the TAACF, NIAID and IDRI (USA). This confirmed the earlier findings that 2-pyridyl-substituted carboxamidrazones were more active than the 4-pyridyl-substituted carboxamidrazones. Another important observation was that upon cyclisation of these carboxamidrazones, a small number of the triazoles retained their activity while in most of the remaining compounds the activity was diminished. This might be attributed to the significant increase in logP value caused by cyclisation of these linear carboxamidrazones, resulting in high lipophilicity and decreased permeability. Another reason might be that the rigidity conferred upon the compound due to cyclisation, results in failure of the compound to fit into the active site of the putative target enzyme. In order to investigate the potential change to the compounds’ metabolism in the organism and/or host, the most active compounds were selected and a fluorine atom was introduced in the pyridine ring. The microbiological results shows a drastic improvement in the activity of the fluorinated carboxamidrazone amides as compared to their non fluorinated counterpart. This improvement in the activity could possibly be the result of the increased cell permeability caused by the fluorine. In a subsidiary strand, a selection of long-chain , -unsaturated carboxylic esters, -keto, -hydroxy carboxylic esters and -keto, -hydroxy carboxylic esters, structurally similar to mycolic acids, were synthesised. The microbiological data revealed that one of the open chain compound was active against the Mycobacterium tuberculosis H37Rv strain and some resistant isolates. The possible compound activity could be its potential to disrupt mycobacterial cell wall synthesis by interfering with the FAS-II pathway.

Catalyst studies on the ring opening of tetrahydrofuran-dimethanol to 1,2,6-hexanetriol

The metal catalyzed hydrogenolysis of the biomass-derived THF-dimethanol to 1,2,6-hexanetriol using heterogeneous catalysts was investigated. Bimetallic Rh-Re catalysts (4 wt% Rh and a Re/Rh (mol. ratio of 0.5) on a silica support gave the best performance and 1,2,6-hexanetriol was obtained in 84% selectivity at 31% conversion (120 C, 80 bar, 4 h); the selectivity reaches a maximum of 92% at 80 C. The product distribution at prolonged reaction times or higher temperatures or both shows the formation of diols and mono-alcohols, indicating that the 1,2,6-hexanetriol is prone to subsequent hydrodeoxygenation reactions. Different silica supports were investigated and optimal results were obtained with an amorphous silica featuring an intermediate surface area and an average mesopore size of about 6 nm. TPR and XPS surface analysis support the presence of mixed Rh and Re particles. The redox Reδ+/ReTotal surface ratio correlates with the conversion in a volcano type dependency. Both gas phase as well as Rh200Re1OH cluster DFT calculations support an acid-metal bifunctional mechanism and explain the products distribution. © 2013 Elsevier B.V. All rights reserved.

Natural killer cell activity in experimental paracoccidioidomycosis of the Syrian hamster

The study evaluated the activity of NK cells during the course of experimental infection of hamsters with Paracoccidioides brasiliensis. Eigthy hamsters were infected with P. brasiliensis by intratesticular route and sacrificed at 24h, 48h, 96h, 1, 2, 4, 8 and 11 weeks of infection and compared to 40 noninfected hamsters employed as controls. These animals were submitted to the study of NK cytotoxic activity by a single-cell assay and humoral immune response by immunodiffusion and ELISA tests. The production of macrophage migration inhibitory factor in the presence of Phyto-hemagglutinin and P. brasiliensis antigen and histopathology of the lesions were evaluated at 1, 4, 8 and 11 weeks of infection. The infected animals displayed significantly high levels of NK activity during the four weeks of infection that decreased from the 8th week on when compared to controls. This impairment of NK activity was associated with depression of cell-mediated immune response and with increase in the extension of the histopathologic lesions. There was an inverse correlation between NK cell activity and specific antibody levels. The results suggest that after initial activation, NK cells were unable to control the fungus dissemination. The impairment of NK activity in the late stages of the infection might be related to immunoregulatory disturbances associated with paracoccidioidomycosis.

Preparation of Achiral and Chiral (E)-Enaminopyran-2,4-diones and Their Phytotoxic Activity

A short and efficient approach to a range of new chiral and achiral functionalized (E)-enaminopyran-2,4-diones starting with commercially available dehydroacetic acid is described. The phytotoxic properties of these (E)-enaminopyran-2,4-diones were evaluated by their ability to interfere with the growth of Sorghum bicolor and Cucumis sativus seedlings. A different sensitivity of the two crops was evident with the (E)-enaminopyran-2,4-diones. The most active compounds were also tested against two weeds, Ipomoea grandifolia and Brachiaria decumbens. To the best of our knowledge, this is the first report describing enaminopyran-2,4-diones as potential plant growth regulators.

July 2012: Volume 1 Issue 4

In this Issue: Progress at the LibraryDacus Library of Winthrop UniversityProgress of Construction, Main Floor, Dacus Library

Influência da chuva na eficácia do glyphosate em mistura com adjuvantes na dessecação de plantas daninhas

Com o objetivo de estudar a influência do momento da chuva após a aplicação do herbicida glyphosate isolado e em mistura com adjuvantes na dessecação de plantas daninhas, foram instalados dois experimentos na Fazenda Experimental de Ensino e Pesquisa da Faculdade de Ciências Agrárias e Veterinárias, UNESP - campus de Jaboticabal-SP, em duas épocas: inverno de 2000 (junho - agosto) e verão de 2001 (janeiro-março). Os experimentos foram instalados no delineamento experimental de blocos ao acaso, em arranjo fatorial 4 (tratamentos herbicidas) x 5 (períodos livres de chuva simulada) + 1, com quatro repetições. Os tratamentos consistiram da combinação de glyphosate SAqC (360 g e.a. ha-1) isolado ou adicionado de uréia (50 g L-1 de calda) ou óleo vegetal (100 ml L-1 de calda) ou sulfato de amônio (100 g L-1 de calda), com cinco períodos de chuva simulada (1, 2, 4, 6 e > 48 horas após a aplicação), além de uma testemunha. A chuva foi simulada com um sistema de irrigação por aspersão, e a quantidade aplicada variou entre 18 e 19 mm. em ambas as épocas a chuva foi prejudicial à ação do glyphosate, principalmente nos menores períodos livres de chuva após a aplicação. Os sintomas de fitointoxicação apareceram mais rapidamente no verão. A utilização de adjuvantes na calda de pulverização não beneficiou o desempenho do herbicida glyphosate no controle das plantas daninhas, no inverno. A adição de uréia (50 g L¹) é uma boa alternativa para o controle de plantas daninhas, no verão, em situações sujeitas à chuva até duas horas após a aplicação.

Natural killer cell activity in experimental paracoccidioidomycosis of the Syrian hamster

Com o objetivo de avaliar a atividade de células natural killer na paracoccidioidomicose experimental do hamster, 80 hamsters foram infectados por via intratesticular com Paracoccidioides brasiliensis e sacrificados após 24h, 48h, 96h, 1, 2, 4, 8 e 11 semanas de infecção. Como controle foram avaliados 40 hamsters normais, não infectados. Os animais foram submetidos ao estudo da atividade citotóxica de células NK pela técnica de single-cell assay e da resposta imune humoral pelas técnicas de imunodifusão dupla e Elisa. A produção do fator inibidor da migração de macrófagos em presença de Phytohemaglutinina e antígeno de P. brasiliensis e a histopatologia das lesões foram estudadas após 1,4, 8e 11 semanas de infecção. Os animais infectados, quando comparados aos controles, apresentaram níveis de atividade NK significativamente elevados durante as 4 primeiras semanas de infecção, havendo diminuição dessa atividade a partir da 8ª semana. Foi observada correlação inversa entre atividade NK e níveis de anticorpos específicos e, associação entre diminuição da atividade NK, depressão de resposta imune celular e aumento da extensão das lesões histopatológicas. Os resultados sugerem que após ativação inicial, as células NK são incapazes de controlar a disseminação do fungo pelos tecidos. A depressão da atividade NK na fase tardia da infecção parece estar relacionada com os distúrbios imunorregulatórios associados à paracoccidioidomicose.

Efeitos dos agentes de impregnação e coberturas comestíveis sobre a secagem e sobre a qualidade física e nutricional do abacaxi

Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

From Craton to Rift: Empirically Based Ground-Truth Criteria for Local Events Recorded on Regional Networks

Region-specific empirically based ground-truth (EBGT) criteria used to estimate the epicentral-location accuracy of seismic events have been developed for the Main Ethiopian Rift and the Tibetan plateau. Explosions recorded during the Ethiopia-Afar Geoscientific Lithospheric Experiment (EAGLE), the International Deep Profiling of Tibet, and the Himalaya (INDEPTH III) experiment provided the necessary GT0 reference events. In each case, the local crustal structure is well known and handpicked arrival times were available, facilitating the establishment of the location accuracy criteria through the stochastic forward modeling of arrival times for epicentral locations. In the vicinity of the Main Ethiopian Rift, a seismic event is required to be recorded on at least 8 stations within the local Pg/Pn crossover distance and to yield a network-quality metric of less than 0.43 in order to be classified as EBGT5(95%) (GT5 with 95% confidence). These criteria were subsequently used to identify 10 new GT5 events with magnitudes greater than 2.1 recorded on the Ethiopian Broadband Seismic Experiment (EBSE) network and 24 events with magnitudes greater than 2.4 recorded on the EAGLE broadband network. The criteria for the Tibetan plateau are similar to the Ethiopia criteria, yet slightly less restrictive as the network-quality metric needs to be less than 0.45. Twenty-seven seismic events with magnitudes greater than 2.5 recorded on the INDEPTH III network were identified as GT5 based on the derived criteria. When considered in conjunction with criteria developed previously for the Kaapvaal craton in southern Africa, it is apparent that increasing restrictions on the network-quality metric mirror increases in the complexity of geologic structure from craton to plateau to rift. Accession Number: WOS:000322569200012