Search results for "Photometry"
showing 10 items of 797 documents
Application of 3-Quinolinoyl Picket Porphyrins to the Electroreduction of Dioxygen to Water: Mimicking the Active Site of Cytochromec Oxidase
2001
International audience
Clarification of the oxidation state of cobalt corroles inheterogeneous and homogeneous catalytic reduction of dioxygen
2008
Co(III) corroles were investigated as efficient catalysts for the reduction of dioxygen in the presence of perchloric acid in both heterogeneous and homogeneous systems. The investigated compounds are (5,10,15-tris(pentafluorophenyl)corrole)cobalt (TPFCor)Co, (10-pentafluorophenyl-5,15-dimesitylcorrole)cobalt (F 5PhMes 2Cor)Co, and (5,10,15-trismesitylcorrole)cobalt (Mes 3Cor)Co, all of which contain bulky substituents at the three meso positions of the corrole macrocycle. Cyclic voltammetry and rotating ring-disk electrode voltammetry were used to examine the catalytic activity of the compounds when adsorbed on the surface of a graphite electrode in the presence of 1.0 M perchloric acid, a…
Polystyrene Sulfonate–Porphyrin Assemblies: Influence of Polyelectrolyte and Porphyrin Structure
2011
In this study, electrostatic self-assembly of different polystyrene sulfonates and a set of tetravalent cationic porphyrins is investigated. It is shown that association of linear polystyrene sulfonates of different molar masses yields finite size nanoscale assemblies that are stable in aqueous solution. Aggregates are compared to the ones of cylindrical brushes, revealing that both form assemblies in the 100 nm range with the charge ratio (molar ratio of porphyrin charges to polyelectrolyte charges) being determining, while the morphology of the resulting network-like assemblies is different for both polyelectrolyte architectures. For the smallest 8k polystyrene sulfonate, in addition, sto…
Posidonia oceanica as a Historical Monitor Device of Lead Concentration in Marine Environment
2005
We show that Posidonia oceanica is able to reliably monitor the variability of environmental lead (Pb). We analyze lead concentration measured in the scales and rhizomes of Posidonia oceanica collected in seven sites along the coasts of the Sicily island and subsequently fractioned them according to a lepidochronological analysis. We measure lead concentration in Posidonia oceanica tissues by using the flame atomic absorption spectrophotometry technique. We compare the measured lead concentration with the estimated lead emission in air due to the gasoline sold and used for combustion in car engines in Sicily. By computation of the Pearson cross-correlation coefficient, we show that lead con…
Cadmium-binding proteins in midgut gland of freshwater crayfishProcambarus clarkii
1989
Metallothioneins, metal binding proteins, were originally isolated and characterized by Margoshes and Vallee. These proteins have a high affinity for various heavy metals, particularly cadmium and mercury and have extensively been studied in mammals. Metal binding proteins have been observed in a variety of marine invertebrates; however, there is very little information available on metal binding proteins in freshwater invertebrates, and particularly in freshwater crustaceans. Cadmium is an ubiquitous non essential element which possesses high toxicity to aquatic organisms. Cadmium binding proteins observed in invertebrates have similar characteristics to mammalian metallothioneins. In 1978…
Targeting the mitochondrial pathway to induce apoptosis/necrosis through ROS by a newly developed Schiff’s base to overcome MDR in cancer
2011
Abstract Multidrug resistance (MDR) in cancer, a major obstacle to successful application of cancer chemotherapy, is often characterized by over-expression of multidrug resistance-related proteins such as MRP1, P-gp or elevated glutathione (GSH) level. Efflux of drugs by functional P-gp, MRP1 and elevated GSH level can confer resistance to apoptosis induced by a range of different stimuli. Therefore, it is necessary to develop new cell death inducers with relatively lower toxicity toward non-malignant cells that can overcome MDR by induction of apoptotic or non-apoptotic cell death pathways. Herein we report the synthesis and spectroscopic characterization of a GSH depleting, redox active S…
Column switching and high-performance liquid chromatography in the analysis of amitriptyline, nortriptyline and hydroxylated metabolites in human pla…
1992
A column-switching system for the direct injection of plasma or serum samples, followed by isocratic high-performance liquid chromatography and ultraviolet detection, is described for the simultaneous quantitation of the tricyclic antidepressant amitriptyline, its demethylated metabolite nortriptyline and the E- and Z-isomers of 10-hydroxyamitriptyline and 10-hydroxynortriptyline. The method included adsorption of amitriptyline and metabolites on a reversed-phase C8 clean-up column (10 microns; 20 mm x 4.6 mm I.D.), washing of unwanted material to waste and, after on-line column-switching, separation on a cyanopropyl analytical column (5 microns; 250 mm x 4.6 mm I.D.). The compounds of inte…
Nanomolar pyrophosphate detection in water and in a self-assembled hydrogel of a simple terpyridine-Zn2+ complex.
2014
A simple terpyridine-Zn(II) complex is shown to act as an efficient and highly selective fluorescent sensor for pyrophosphate in water at physiological pH. The sensor complex showed an unprecedented fluorescence response (∼500 fold increase) and a record nanomolar sensitivity (detectable fluorescent response at 20 nM and LOD ∼ 0.8 nM). It has successfully been used to stain and record confocal fluorescence microscopy images of HeLa cells. Moreover, the complex was found to self-assemble into a hydrogel which was subsequently used to coat disposable paper strips for easy, low-cost detection of pyrophosphate.
The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
2014
Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the one used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explo…
Quasi-stellar objects in the ALHAMBRA survey
2012
[Context]: Even the spectroscopic capabilities of today's ground and space-based observatories can not keep up with the enormous flow of detections (>10 5 deg -2) unveiled in modern cosmological surveys as: i) would be required enormous telescope time to perform the spectroscopic follow-ups and ii) spectra remain unattainable for the fainter detected population. In the past decade, the typical accuracy of photometric redshift (photo-z) determination has drastically improved. Nowdays, it has become a perfect complement to spectroscopy, closing the gap between photometric surveys and their spectroscopic follow-ups. The photo-z precision for active galactic nuclei (AGN) has always lagged behin…