Search results for "Concentration"
showing 10 items of 1906 documents
Molecular Cloning, Heterologous Expression, and Characterization of Ornithine Decarboxylase from Oenococcus oeni
2011
International audience; Ornithine decarboxylase (ODC) is responsible for the production of putrescine, the major biogenic amine found in wine. Oenococcus oeni is the most important lactic acid bacterium in the winemaking process and is involved in malolactic fermentation. We report here the characterization of ODC from an O. oeni strain isolated from wine. Screening of 263 strains isolated from wine and cider from all over the world revealed that the presence of the odc gene appears to be strain specific in O. oeni. After cloning, heterologous expression in Escherichia coli, and characterization, the enzyme was found to have a molecular mass of 85 kDa and a pI of 6.2 and revealed maximal ac…
Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy.
2014
The effects of increasing atmospheric CO2 on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO2 gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 mu atm, minimum Omega(arag) 3.77), moderately CO2-enriched (median pCO(2) 592 mu atm, minimum Omega(arag) 2.96), and highly CO2-enriched (median pCO(2) 1611 mu at…
Prevalence of heterotrophic methylmercury detoxifying bacteria across oceanic regions
2022
10 pages, 4 figures, 1 table, supporting information https://doi.org/10.1021/acs.est.1c05635
Nanoprobing the acidification process during intracellular uptake and trafficking
2015
Abstract Many nanoparticular drug delivery approaches rely on a detailed knowledge of the acidification process during intracellular trafficking of endocytosed nanoparticles (NPs). Therefore we produced a nanoparticular pH sensor composed of the fluorescent pH-sensitive dual wavelength dye carboxy seminaphthorhodafluor-1 (carboxy SNARF-1) coupled to the surface of amino-functionalized polystyrene NPs (SNARF-1-NP). By applying a calibration fit function to confocal laser scanning microscopy (CLSM) images, local pH values were determined. The acidification and ripening process of endo/lysosomal compartments containing nanoparticles was followed over time and was found to progress up to 6h to …
Evolution and biomineralization of pteropod shells
2021
12 pages; International audience; Shelled pteropods, known as sea butterflies, are a group of small gastropods that spend their entire lives swimming and drifting in the open ocean. They build thin shells of aragonite, a metastable polymorph of calcium carbonate. Pteropod shells have been shown to experience dissolution and reduced thickness with a decrease in pH and therefore represent valuable bioindicators to monitor the impacts of ocean acidification. Over the past decades, several studies have highlighted the striking diversity of shell microstructures in pteropods, with exceptional mechanical properties, but their evolution and future in acidified waters remains uncertain. Here, we re…
Melatonin activates the peroxidase-oxidase reaction and promotes oscillations.
2001
We have studied the peroxidase-oxidase reaction with NADH and O2 as substrates and melatonin as a cofactor in a semibatch reactor. We show for the first time that melatonin is an activator of the reaction catalyzed by enzymes from both plant and animal sources. Furthermore, melatonin promotes oscillatory dynamics in the pH range from 5 to 6. The frequency of the oscillations depends on the pH such that an increase in pH was accompanied by a decrease in frequency. Conversely, an increase in the flow rate of NADH or an increase in the average concentration of NADH resulted in an increase in oscillation frequency. Complex dynamics were not observed with melatonin as a cofactor. These results a…
Retinyl ester hydrolases in retinal pigment epithelium.
1991
In bovine retinal pigment epithelium membranes we have found three hydrolases which were active against trans-retinyl palmitate. This was possible by assaying different subcellular fractions as a function of pH in the range 3-9. Detection of these activities has been favored by the use in the enzyme assay of Triton X-100, which has an activating effect up to a concentration of 0.03% at a detergent-protein ratio of about 1.5-3.0. Apparent kinetic parameters for the retinyl ester hydrolases have been determined after a study of the optimization of assay conditions. Vmax values for hydrolases acting at pH 4.5, 6.0, and 7.0 were, respectively, 156, 55, and 70 nmol/h/mg. To identify the subcellu…
Quantification of hydrolysis of toxic organophosphates and organophosphonates by diisopropyl fluorophosphatase from Loligo vulgaris by in situ Fourie…
2008
Abstract The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris effectively catalyzes the hydrolysis of diisopropyl fluorophosphate (DFP) and a number of organophosphorus nerve agents, including sarin, soman, cyclosarin, and tabun. Up to now, the determination of kinetic data has been achieved by techniques such as pH-stat titration, ion-selective electrodes, and fluorogenic substrate analogs. We report a new assaying method using in situ Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection (ATR) for the real-time determination of reaction rates. The method employs changes in the P–O–R stretching vibration of DFP and nerve agent substrate…
UDP-glucosyltransferase activity toward exogenous substrates in Drosophila melanogaster.
1991
To investigate the capacity of Drosophila extracts to glucosylate exogenous substrates we have developed a fast and sensitive method for the detection of UDP-glucosyltransferase activity using 4-nitrophenol, 1-naphthol, or 2-naphthol as substrates. High-performance liquid chromatography was used to separate and quantitate the reaction products, allowing detection of activities that produced as little as 1 pmol of 2-naphthol glucoside (fluorescence detection) or 16 pmol of 4-nitrophenol glucoside (absorbance detection). Optimal activity was found at 43 degrees C and alkaline pH. The affinity of the Drosophila enzyme was 250-fold higher for 1-naphthol or 2-naphthol (Km approximately 4 microM)…
Small unilamellar liposomes from mixed natural and polymeric phospholipids: stability and susceptibility to phospholipase A2.
1991
The concept of the uncorkable liposome composed of phase-separated mixtures of a polymerized phospholipid and an enzymically digestible phospholipid has been investigated, using small unilamellar vesicles composed of mixtures of (polymerized) dienoylphosphatidylcholine (DENPC) and dimyristoylphosphatidylcholine (DMPC). Mixed liposomes, even those containing only 10% DENPC, were much more stable than DMPC liposomes, as indicated by the release of entrapped [3H]inulin or [14C]glucose. DMPC liposomes released entrapped solute on exposure to phospholipase A2, whereas mixed vesicles were resistant. The results are compared with those of an earlier study on monolayers of similar compositions. It …