26 research outputs found

    Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganisms†

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    A series of [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives have been synthesised as potential indicators of microbial nitroreductase activity. When assessed against a selection of 20 clinically important pathogenic microorganisms, microbial colonies of various colours (yellow, green, red, brown, black) were produced and attributed to nitroreductase activity. Most substrates elicited colour responses with Gram-negative microorganisms. In contrast, the growth of several species of Gram-positive microorganisms and yeasts was often inhibited by the substrates and hence coloured responses were not seen. Graphical abstract: Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganism

    Detection of Microbial Nitroreductase Activity by Monitoring Exogenous Volatile Organic Compound Production Using HS-SPME-GC-MS

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    Development of a rapid approach for universal microbial detection is required in the healthcare, food and environmental sectors to aid with medical intervention, food safety and environmental protection. This research investigates the use of enzymatic hydrolysis of a substrate by a microorganism to generate a volatile organic compound (VOC). One such enzyme activity that can be used in this context is nitroreductase as such activity is prevalent across a range of microorganisms. A study was developed to evaluate a panel of 51 microorganisms of clinical interest for their nitroreductase activity. Two enzyme substrates, nitrobenzene and 1-fluoro-2-nitrobenzene, were evaluated for this purpose with evolution, after incubation, of the VOCs aniline and 2-fluoroaniline, respectively. Detection of the VOCs was done using headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) with obtained limits of quantitation (LOQ) of 0.17 and 0.03 µg/mL for aniline and 2-fluoroaniline, respectively. The results indicated that both enzyme substrates were reduced by the same 84.3% of microorganisms producing the corresponding volatile anilines which were detected using HS-SPME-GC-MS. It was found that nitroreductase activity could be detected after 6–8 h of incubation for the selected pathogenic bacteria investigated. This approach shows promise as a rapid universal microbial detection system

    Fluorogenic L-alanylaminopeptidase substrates derived from 6-amino-2-hetarylquinolines and 7-amino-3-hetarylcoumarins and their potential applications in diagnostic microbiology

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    Six novel fluorogenic enzyme substrates for detecting L-alanylaminopeptidase activity in microorganisms have been prepared and evaluated in Columbia agar media. The substrates are L-alanyl derivatives of 6-amino-2-hetarylquinolines and 7-amino-3-hetarylcoumarins. Both the quinoline and coumarin series of substrates produced fluorescence in the presence of Gram-negative microorganisms. In contrast, fluorescence generation in the presence of the Gram-positive microorganisms and yeasts was limited or absent

    Fluorogenic 7-azidocoumarin and 3/4-azidophthalimide derivatives as indicators of reductase activity in microorganisms

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    A series of fluorogenic heterocyclic azides were prepared and assessed as reductase substrates across a selection of Gram-negative and Gram-positive microorganisms. The majority of these azides showed similar activity profiles to nitroreductase substrates. Microorganisms that do not produce hydrogen sulfide reduced the azides, indicating reductase activity was not linked to hydrogen sulfide production.A series of fluorogenic heterocyclic azides were prepared and assessed as reductase substrates across a selection of Gram-negative and Gram-positive microorganisms. The majority of these azides showed similar activity profiles to nitroreductase substrates. Microorganisms that do not produce hydrogen sulfide reduced the azides, indicating reductase activity was not linked to hydrogen sulfide production

    BioTIME:a database of biodiversity time series for the Anthropocene

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    Abstract Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community‐led open‐source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km² (158 cm²) to 100 km² (1,000,000,000,000 cm²). Time period and grain: BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates. Software format: .csv and .SQL

    The Synthesis of L-Alanyl and β-Alanyl Derivatives of 2-Aminoacridone and Their Application in the Detection of Clinically-Important Microorganisms.

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    In clinical microbiology the speed with which pathogenic microorganisms may be detected has a direct impact on patient health. One important strategy used in the laboratory is the growth of cultures in the presence of an enzymatic substrate which, once transformed by the appropriate microbial enzyme, generates a detectable colour or fluorescence output. Such substrates have previously been prepared by our group and others and are available as commercial diagnostic kits, however they all suffer from some degree of diffusion when used in a solid growth medium. This diffusion complicates the detection and differentiation of species in polymicrobial cultures and so we sought to improve on our previous work. In this work we have prepared and evaluated a series of novel fluorogenic enzyme substrates based on N-substituted-2-aminoacridones. All of the prepared substrates were found to be suitable for the detection and differentiation of certain microorganisms, however those based on the 2-amino-10-benzylacridone core in particular showed no apparent diffusion when incorporated into solid growth media. On transformation these substrates generated brightly fluorescent colonies that are clearly contrasted with the background medium due to the difference in emission wavelength (λem 445-450 nm for the substrate, λem 550 nm for the product). Here we have shown that our L-alanyl aminopeptidase substrate, 2-(N-L-alanylamino)-10-benzylacridone, is particularly suited to the detection of Gram-negative bacteria, and our β-alanyl aminopeptidase substrate, 2-(N- β-alanylamino)-10-benzylacridone, to the detection of Pseudomonas aeruginosa and Serratia marcescens when grown on solid media incorporating these substrates. The resulting fluorophore shows no apparent diffusion from the colonies of interest, and the enhanced sensitivity offered by fluorescent emission may allow for the detection of these organisms as microcolonies using automated fluorescence microscopy

    Use of volatile compounds as a diagnostic tool for the detection of pathogenic bacteria

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    The analysis of volatile compounds (VCs) generated by bacteria has been proposed as a possible alternative method for the identification of pathogenic bacteria. Further investigations into the VCs generated by many different species and strains of the same species are required alongside the use of consistent growth conditions and procedures throughout VC analysis. Consequently, the true potential of the detection of bacterial VCs as a diagnostic tool in the identification of pathogenic bacteria in clinical and food samples can be determined

    Synthesis of 2-arylbenzothiazole derivatives and their application in bacterial detection

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    A series of 2-arylbenzothiazole derivatives have been prepared as fluorogenic enzyme substrates in order to detect aminopeptidase, esterase, phosphatase and β-galactosidase activity in clinically important Gram-negative and Gram-positive bacteria. Substrates were incorporated into an agar-based culture medium and this allowed growth of intensely fluorescent bacterial colonies based on hydrolysis by specific enzymes. Substrate 20 targeted l-alanine aminopeptidase activity and was hydrolysed exclusively by a range of Gram-negative bacteria and inhibited the growth of a range of Gram-positive bacteria. Substrate 19a targeted β-alanyl aminopeptidase activity and generated fluorescent colonies of selected Gram-negative species including Pseudomonas aeruginosa. Substrate 21b targeted C8-esterase activity and resulted in strongly fluorescent colonies of selected species known to harbour such enzyme activity (e.g., Salmonella and Pseudomonas). Most Gram-negative species produced colonies with an intense blue fluorescence due to hydrolysis of phosphatase substrates 24a-c and substrate 24c was also hydrolysed by strains of Staphylococcus aureus. Compounds 26b and 26c targeted β-galactosidase activity and generated strongly fluorescent colonies with coliform bacteria that produced this enzyme (e.g., Escherichia coli)

    An Efficient Process for Pd-Catalyzed C−N Cross-Coupling Reactions of Aryl Iodides: Insight Into Controlling Factors

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    An investigation into Pd-catalyzed C−N cross-coupling reactions of aryl iodides is described. NaI is shown to have a significant inhibitory effect on these processes. By switching to a solvent system in which the iodide byproduct was insoluble, reactions of aryl iodides were accomplished with the same efficiencies as aryl chlorides and bromides. Using catalyst systems based on certain biarylphosphine ligands, aryl iodides were successfully reacted with an array of primary and secondary amines in high yields. Lastly, reactions of heteroarylamines and heteroaryliodides were also conducted in high yields.National Institutes of Health (U.S.) (Grant GM-58160)Merck & Co., Inc.BASFChemetallWilliam Asbornsen Albert Memorial Fund (Fellowship)National Science Foundation (U.S.) (Grant CHE 9808061)National Science Foundation (U.S.) (Grant DBI 9729592
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