Search results for "fluorescence"
showing 10 items of 2463 documents
Where Does Nε-Trimethyllysine for the Carnitine Biosynthesis in Mammals Come from?
2014
N(ε)-trimethyllysine (TML) is a non-protein amino acid which takes part in the biosynthesis of carnitine. In mammals, the breakdown of endogenous proteins containing TML residues is recognized as starting point for the carnitine biosynthesis. Here, we document that one of the main sources of TML could be the vegetables which represent an important part of daily alimentation for most mammals. A HPLC-ESI-MS/MS method, which we previously developed for the analysis of N(G)-methylarginines, was utilized to quantitate TML in numerous vegetables. We report that TML, believed to be rather rare in plants as free amino acid, is, instead, ubiquitous in them and at not negligible levels. The occurrenc…
Green direct determination of mineral elements in artichokes by infrared spectroscopy and X-ray fluorescence.
2015
Near infrared (NIR) and X-ray fluorescence (XRF) spectroscopy were investigated to predict the concentration of calcium, potassium, iron, magnesium, manganese and zinc in artichoke samples. Sixty artichokes were purchased from different Spanish areas (Benicarlo, Valencia and Murcia). NIR and XRF spectra, combined with partial least squares (PLS) data treatment, were used to develop chemometric models for the prediction of mineral concentration. To obtain reference data, samples were mineralised and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Coefficients of determination obtained for the regression between predicted values and reference ones for calcium, …
Azo-Sulforhodamine Dyes: A Novel Class of Broad Spectrum Dark Quenchers
2014
A rapid access to a novel class of water-soluble dark quencher dyes was achieved using an azo-coupling reaction between a fluorescent primary arylamine derived from a sulforhodamine 101 scaffold and a tertiary aniline equipped with different bioconjugatable groups. The thus obtained nonfluorescent azo-sulforhodamine hybrids display a broad quenching range spanning the visible to NIR regions. This was demonstrated through the preparation and enzymatic activation of FRET-based fluorogenic substrates of urokinase.
Study of the diurnal cycle of stressed vegetation for the improvement of fluorescence remote sensing
2006
Chlorophyll fluorescence (Chf) emission allows estimating the photosynthetic activity of vegetation - a key parameter for the carbon cycle models - in a quite direct way. However, measuring Chf is difficult because it represents a small fraction of the radiance to be measured by the sensor. This paper analyzes the relationship between the solar induced Chf emission and the photosynthetically active radiation (PAR) in plants under water stress condition. The solar induced fluorescence emission is measured at leaf level by means of three different methodologies. Firstly, an active modulated light fluorometer gives the relative fluorescence yield. Secondly, a quantitative measurement of the Ch…
Sensitivity analysis of the fraunhofer line discrimination method for the measurement of chlorophyll fluorescence using a field spectroradiometer
2007
The Fraunhofer Line Discrimination (FLD) principle is established as a good method for remote sensing of solar induced chlorophyll fluorescence. Some improvements to the method are analysed in order to determine and reduce the sources of error in the estimation of the fluorescence emission. A sensitivity analysis has been performed over simulated data generated from real diurnal cycle measurements.
X-ray irradiation effects on fluorine-doped germanosilicate optical fibers
2014
International audience; We report an experimental investigation on the effects of fluorine codoping on the radiation response of Ge-doped Optical Fibers (OFs) obtained by three different drawing conditions. The OFs were irradiated with 10 keV X-rays up to 300 Mrad and studied by online Radiation-Induced-Attenuation (RIA) measurements. Confocal Micro- Luminescence (CML) and Electron Paramagnetic Resonance (EPR) were also employed to investigate the permanent radiation-induced-defects. The variation of the Germanium-Lone-Pair-Center (GLPC) and Non-Bridging- Oxygen-Hole-Centers (NBOHC) concentration with the radiation dose is investigated by CML, whereas the ones of the induced Ge(1), Ge(2) an…
Influence of neutron and gamma-ray irradiations on rad-hard optical fiber
2015
We investigated point defects induced in rad-hard Fluorine-doped optical fibers using both a mixed source of neutrons (fluences from 1015 to 1017 n/cm2) and γ-rays (doses from 0.02 to 2 MGy) and by a γ-ray source (dose up to 10 MGy). By combining several complementary spectroscopic techniques such as radiation-induced attenuation, confocal micro-luminescence, time-resolved photo-luminescence and electron paramagnetic resonance, we evidenced intrinsic and hydrogen-related defects. The comparison between the two irradiation sources highlights close similarities among the spectroscopic properties of the induced defects and the linear correlation of their concentration up to 1016 n/cm2. These r…
Effects of 2-month ozone exposure in spinach leaves on photosynthesis, antioxidant systems and lipid peroxidation
2003
The photosynthesis response, antioxidant systems and lipid peroxidation were studied in leaves from spinach plants (Spinacia oleracea L.) in response to ozone fumigation, ambient air and charcoal filtered air treatments. The photosynthetic activity was tested through gas exchange and chlorophyll a fluorescence measurements. Ambient air and ozone fumigation caused a decrease in the photosynthetic rate (25% and 63%, respectively) mainly due to a reduced mesophyll activity, as evidenced by the increased intercellular CO, concentration. These data agree with a large reduction in the non-cyclic electron flow (7% and 16%), a lower capacity to reduce the quinone pool and a higher development of no…
Response of Spinach Leaves (Spinacia oleracea L.) to Ozone Measured by Gas Exchange, Chlorophyll a Fluorescence, Antioxidant Systems, and Lipid Perox…
2004
Spinach (Spinacia oleracea L. cv. Clermont) leaves grown in open-top chambers and exposed to three different concentrations of ozone were measured for gas exchange, chlorophyll a fluorescence, antioxidant systems, and lipid peroxidation at the end of growing season. High O-3 concentration reduced F-v/F-m, indicating that the efficiency in the energy conversion of photosystem 2 (PS2) was altered. The rate of non-cyclic electron transport rate and the capacity to reduce the quinone pool were also affected. The development of non-photochemical quenching was not high enough to decrease the photon excess in the PS2. The limitation of photosynthetic activity was probably correlated with stomata c…
Real-time fluorescence image-guided gastrointestinal oncologic surgery: Towards a new era
2021
Technological improvements are crucial in the evolution of surgery. Real-time fluorescence-guided surgery (FGS) has spread worldwide, mainly because of its usefulness during the intraoperative decision-making processes. The success of any gastrointestinal oncologic resection is based on the anatomical identification of the primary tumor and its regional lymph nodes. FGS allows also to evaluate the blood perfusion at the gastrointestinal stumps after colorectal or esophageal resections. Therefore, a reduction on the anastomotic leak rates has been postulated as one of the foreseeable benefits provided by the use of FGS in these procedures. Although the use of fluorescence in lymph node detec…