Search results for "Fluorescence"
showing 10 items of 2463 documents
Seasonal and Inter-annual Variation of Evapotranspiration in Amazonia Based on Precipitation, River Discharge and Gravity Anomaly Data
2019
We analyzed seasonal and spatial variations of evapotranspiration (ET) for five Amazon sub-basins and their response to the 2015/16 El Nino episode using a recently developed water-budget approach. ET varied typically between similar to 7 and 10 cm/month with exception of the Xingu basin for which it varied between 10 and 15 cm/month. Outstanding features of ET seasonality are (i) generally weak seasonality, (ii) two ET peaks for the two very wet catchments Solimoes and Negro, with one occurring during the wet season and one during the drier season, and (iii) a steady increase of ET during the second half of the dry season for the three drier catchments (Madeira, Tapajos, Xingu). Peak ET oc…
Mercury and selenium in fish and shellfish: Occurrence, bioaccessibility and uptake by Caco-2 cells
2012
This study evaluates Hg and Se concentrations and bioaccessibility (element solubilised after simulated gastrointestinal digestion) in 16 raw seafood species consumed in Spain. The concentrations varied greatly (Hg, 3.8-1621 ng/g wet weight, ww; Se, 84-1817 ng/g ww). Only one sample of swordfish exceeded the Hg limit permitted in Spain (1mg/kg), and for this sample the Hg/Se molar ratio and Se Health Benefit Value food safety criteria also indicated the presence of a risk. Bioaccessibility of Hg (35-106%) and Se (17-125%) was very variable and the Hg/Se molar ratio in the bioaccessible fraction was less than one for all samples. Transport by Caco-2 cells, an intestinal epithelium model, was…
Interactions between aroma compounds and beta-lactoglobulin in the heat-induced molten globule state
2010
; he present study aims to elucidate the binding of small hydrophobic ligands onto the molten globule state of β-lactoglobulin (BLG). The conversion of the native BLG into a molten globule state was induced by heat treatment at acidic pH. The molten globule state was evidenced by far and near-UV circular dichroism spectra. β-Ionone and guaiacol exhibited a higher binding ability to BLG in the heat-induced molten globule state compared to unheated BLG, as assessed by protein surface hydrophobicity measurements, using 6-propionyl-2-(dimethylamino)naphthalene (PRODAN) fluorescent probe. The binding sites of the two aroma compounds were determined by 2D nuclear magnetic resonance (NMR) spectro…
Concentration of ochratoxin A in wines from supermarkets and stores of Valencian Community (Spain)
2004
Ochratoxin A (OTA) is a mycotoxin produced by fungi species belonging to the genera Aspergillus and Penicillium being isolated in alcoholic beverages. The aim of this work is developed and applied a procedure for the analysis of OTA in wines. An analytical method based on immunoaffinity column (IAC) for clean-up, liquid chromatography with fluorescence detection (LC-FD), and LC-FD after of OTA methylation was used to determine the occurrence of OTA in wines. Recoveries of this mycotoxin spiked to red wines at 0.5 ng/ml level were >90% with an average of relative standards deviations of 4%. Furthermore, 116 wine samples from designation of origin (DO) and three samples from food stores of Va…
EXAFS studies on the local structure of Er3+ ions in silica xerogels co-doped with aluminium
2001
The local environment around Er3+ ions in wet and densified (at 900°C) silica xerogels (pure and co-doped with aluminium) has been studied at the Er L3-edge by X-ray absorption spectroscopy using the fluorescence detection technique. The radial distribution functions (RDF), reconstructed from X-ray absorption fine structure (EXAFS), show several changes in the local co-ordination of erbium ions upon densification: shortening of the Er-O and Er-Si/Al distances, decrease of the co-ordination numbers and broadening of the Er-O RDF. The effect of Al co-doping is clearly discerned by EXAFS in both the first and second co-ordination shells for densified gels and mainly in the second shell for wet…
First on-line laser spectroscopy of radioisotopes of a refractory element
1999
The first fully on-line isotope shift measurement of a radioactive refractory element is reported. Collinear laser-induced fluorescence measurements were made on the radioactive isotopes ${}^{170,172,173,174}\mathrm{Hf}$ produced with a flux of $2--3\ifmmode\times\else\texttimes\fi{}{10}^{3}$ ions per second from an ion-guide fed isotope separator. The method may be applied to all elements and isomers with lifetimes as short as 1 ms. The systematics of the new charge radii measurements are well reproduced by theory, with the maximum deformation in the chain occurring significantly below the midshell.
Synthesis, stability and spectral behavior of fluorogenic sulfone-pyronin and sulfone-rosamine dyes
2018
International audience; The first synthesis of sulfone-pyronin and sulfone-rosamine dyes bearing optically tunable primary amino groups (acting as fluorogenic centers) is presented. Sulfone analogs of xanthene-based fluorophores have recently been highlighted as a new class of near-infrared (NIR) fluorescent dyes (Liu et al. ACS Appl Mater Interfaces 2016; 8(35):22953-62), and the availability of fluorogenic derivatives is essential for the rapid construction of “turn-on” reactive probes for chemoselective bioimaging. However, these fluorescent anilines have been found to be unstable in aqueous physiological conditions due to the marked electrophilicity of their meso-position and hence its …
Synthesis of new asymmetric xanthene dyes via catalyst-free SNAr with sulfur nucleophiles
2014
Addition of a single functional handle to the tricyclic moiety of fluorescein results in asymmetric xanthene dyes. Our synthesis of a new class of asymmetric xanthenes proceeds via an unusual SNAr with sulfur nucleophiles on electron rich aromatic xanthenes scaffolds in the absence of a metal catalyst. The resulting 3'-thioethers exhibit high photostability and are conveniently converted into reactive dyes for macromolecule labelling.
Ultrafast Dynamics of Dansylated POPAM Dendrimers and Energy Transfer in their Dye Complexes
2009
We have studied internal dynamics of dansylated poly(propyleneamine) dendrimers of different generations in solution and excitation energy transfer from dansyl chromophores to xanthene dyes that form van der Waals complexes with the dendrimers
Increased electron donor and electron acceptor characters enhance the adhesion between oil droplets and cells of Yarrowia lipolytica as evaluated by …
2003
The adhesion of methyl ricinoleate droplets to cells of the yeast Yarrowia lipolytica was investigated. A new cytometric method, relying on the double staining of fatty globules with Nile Red and of cells with Calcofluor, enabled us to quantify methyl ricinoleate droplet adhesion to cells precultured on a hydrophilic or on a hydrophobic carbon source. In this last case, droplet adsorption was enhanced and a MATS (microbial adhesion to solvents) test revealed that this increase was due to Lewis acid-base interactions and not to an increase in the hydrophobic properties of the cell surface. These preliminary results demonstrate that the developed cytometric method is promising for various app…