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A series of 2,3-disubstituted pyridines and pyrido[2,3-d]pyridazines have been synthesized. The molecular structure of the compounds have been elucidated by using chromatography; ir, nmr, and mass spectrometry; and chemical methods, in particular metal complexation. The new compounds offer interesting chemistry and are envisaged to function as potential chemotherapeutic and pharmacodynamic agents. 相似文献
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A novel process is described to efficiently photoconvert low-grade organic materials such as waste biomass into natural biological
plastics. When heterogeneous forms of dry biomass are thermally gasified, relatively homogeneous synthesis gas mixtures composed
primarily of carbon monoxide and hydrogen are produced. Unique strains of photosynthetic bacteria were isolated that nearly
quantitatively photoassimilate the carbon monoxide and hydrogen components of synthesis gas into new cell mass. Under unbalanced
culture conditions when cellular growth is limited by shortages of nitrogen, calcium, magnesium, iron, or essential vitamins,
up to 28% of the new cell mass is found as granules of poly-3-hydroxyalkanoate (PHA), a highmolecular-weight thermoplastic
that can be solvent-extracted. The dominant monomeric unit of PHAs is 3-hydroxybutyrate (3HB), which is polymerized into the
homopolymeric poly-3-hydroxybutyrate (PHB). PHB is marketed as a biodegradable plastic with physical properties similar to
polystyrene. When a green alga was cocultured with the photosynthetic bacterium in light-dark (day-night) cycles, the bacteria
synthesized a polymer of poly-3-hydroxybutyrate-3-hydroxyvalerate (PHB-V) with a composition of 70% 3HB and 30% 3-hydroxyvalerate
(3HV) to an extent of 18% of the new cell mass. PHB-V is commercially marketed as Biopol and has physical properties similar
to polypropylene or polyethylene. Our results demonstrate that a strain of photosynthetic bacteria capable of photoassimilating
synthesis gas or producer gas is a potential candidate for large-scale production of biological polyesters. 相似文献
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Bactericidal mode of titanium dioxide photocatalysis 总被引:38,自引:0,他引:38
Zheng Huang Pin-Ching Maness Daniel M. Blake Edward J. Wolfrum Sharon L. Smolinski William A. Jacoby 《Journal of photochemistry and photobiology. A, Chemistry》2000,130(2-3):163-170
When exposed to near-UV light, titanium dioxide (TiO2) exhibits a strong bactericidal activity. However, the killing mechanism(s) underlying the TiO2 photocatalytic reaction is not yet well understood. The aim of the present study is to investigate the cellular damage sites and their contribution to cell death. A sensitive approach using o-nitrophenol β-
galactopyranosideside (ONPG) as the probe and Escherichia coli as model cells has been developed. This approach is used to illustrate damages to both the cell envelope and intracellular components caused by TiO2 photocatalytic reaction. Treatment of E. coli with TiO2 and near-UV light resulted in an immediate increase in permeability to small molecules such as ONPG, and the leakage of large molecules such as β-
galactosidase after 20 min. Kinetic data showed that cell wall damage took place in less than 20 min, followed by a progressive damage of cytoplasmic membrane and intracellular components. The results from the ONPG assay correlated well with the loss of cell viability. Cell wall damage followed by cytoplasmic membrane damage leading to a direct intracellular attack has therefore been proposed as the sequence of events when microorganisms undergo TiO2 photocatalytic attack. It has been found that smaller TiO2 particles cause quicker intracellular damage. Evidence has been obtained that indicated that the TiO2 photocatalytic reaction results in continued bactericidal activity after the UV illumination terminates. 相似文献
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Erythromycin forms association complexes with four sulfonic acid dyes that can be extracted into chloroform and quantified by spectrophotometry. Of the dyes studied, MO and O IV form 1:1 complexes with the conjugate acid of erythromycin. Solutions containing 20 to 100 μg/ml of erythromycin can be conveniently analyzed by use of MO and the method described. 相似文献
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Most cryopreservation procedures are optimized using a small number of germplasm accessions. We classified the garlic (Allium sativum L.) accessions that were selected for our studies based on genotype as identified using amplified fragment length polymorphism markers. Although recovery was variable, shoots regenerated from a broad range of the accessions after cryo-exposure. Garlic shoot tips were excised from cloves, surface sterilized, and placed on media at 5 degree C for 2 days prior to cryopreservation. Shoot tips were then treated with sucrose-glycerol for 20 minutes, plant vitrification solution 2 (PVS2; 15 percent w/v ethylene glycol, 15 percent w/v DMSO, 30 percent w/v glycerol, 13.7 percent w/v sucrose) at 0 degree C, and then plunged on foils into liquid nitrogen slush. Explants were recovered in 1.2 M sucrose for 20 minutes and then plated onto Gamborgs B5 medium containing alpha-naphthaleneacetic acid (NAA) and 6-(gammagamma-dimethylallylamino purine) (2-iP). Our results demonstrate that genotypically diverse accessions of garlic can be successfully cryopreserved. 相似文献
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A sensitive procedure has been developed for analysis of solutions of the macrolide antibiotic, erythromycin. The method is based on ion-pair formation of the conjugate acid of the drug with an 35S-labeled isostere of methyl orange, partitioning into chloroform and measurement by liquid scintillation spectrometry. Acceptable accuracy and precision are achieved with the devised technique for solutions of erythromycin in the concentration range of 1 to 10 μg/ml. 相似文献
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