Highly Sensitive Fluorescence Probe Based on Functional SBA-15 for Selective Detection of Hg2+

An inorganic–organic hybrid fluorescence chemosensor (DA/SBA-15) was prepared by covalent immobilization of a dansylamide derivative into the channels of mesoporous silica material SBA-15 via (3-aminopropyl)triethoxysilane (APTES) groups. The primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. Fluorescence characterization shows that the obtained inorganic–organic hybrid composite is highly selective and sensitive to Hg2+ detection, suggesting the possibility for real-time qualitative or quantitative detection of Hg2+ and the convenience for potential application in toxicology and environmental science

Contrast Adaptation Contributes to Contrast-Invariance of Orientation Tuning of Primate V1 Cells

BACKGROUND: Studies in rodents and carnivores have shown that orientation tuning width of single neurons does not change when stimulus contrast is modified. However, in these studies, stimuli were presented for a relatively long duration (e. g., 4 seconds), making it possible that contrast adaptation contributed to contrast-invariance of orientation tuning. Our first purpose was to determine, in marmoset area V1, whether orientation tuning is still contrast-invariant with the stimulation duration is comparable to that of a visual fixation. METHODOLOGY/PRINCIPAL FINDINGS: We performed extracellular recordings and examined orientation tuning of single-units using static sine-wave gratings that were flashed for 200 msec. Sixteen orientations and three contrast levels, representing low, medium and high values in the range of effective contrasts for each neuron, were randomly intermixed. Contrast adaptation being a slow phenomenon, cells did not have enough time to adapt to each contrast individually. With this stimulation protocol, we found that the tuning width obtained at intermediate contrast was reduced to 89% (median), and that at low contrast to 76%, of that obtained at high contrast. Therefore, when probed with briefly flashed stimuli, orientation tuning is not contrast-invariant in marmoset V1. Our second purpose was to determine whether contrast adaptation contributes to contrast-invariance of orientation tuning. Stationary gratings were presented, as previously, for 200 msec with randomly varying orientations, but the contrast was kept constant within stimulation blocks lasting >20 sec, allowing for adaptation to the single contrast in use. In these conditions, tuning widths obtained at low contrast were still significantly less than at high contrast (median 85%). However, tuning widths obtained with medium and high contrast stimuli no longer differed significantly. CONCLUSIONS/SIGNIFICANCE: Orientation tuning does not appear to be contrast-invariant when briefly flashed stimuli vary in both contrast and orientation, but contrast adaptation partially restores contrast-invariance of orientation tuning

Fluorescent ion-imprinted polymers for selective Cu(II) optosensing

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)This paper describes the synthesis and characterization of a fluorescent ion-imprinted polymer (IIP) for selective determination of copper ions in aqueous samples. The IIP has been prepared using a novel functional monomer, 4-[(E)-2-(4'-methyl-2,2'-bipyridin-4-yl)vinyl]phenyl methacrylate (abbreviated as BSOMe) that has been spectroscopically characterized in methanolic solution, in the absence and in the presence of several metal ions, including Cd(II), Cu(II), Hg(II), Ni(II), Pb(II), and Zn(II). The stability constant (2.04 x 10(8) mol(-2) l(2)) and stoichiometry (L2M) of the BSOMe complex with Cu(II) were extracted thereof. Cu(II)-IIPs were prepared by radical polymerization using stoichiometric amounts of the fluorescent monomer and the template metal ion. The resulting cross-linked network did not show any leaching of the immobilized ligand allowing determination of Cu(II) in aqueous samples by fluorescence quenching measurements. Several parameters affecting optosensor performance have been optimized, including sample pH, ionic strength, or polymer regeneration for online analysis of water samples. The synthesized Cu(II)-IIP exhibits a detection limit of 0.04 mu mol l(-1) for the determination of Cu(II) in water samples with a reproducibility of 3%, exhibiting an excellent selectivity towards the template ion over other metal ions with the same charge and close ionic radius. The IIP-based optosensor has been repeatedly used and regenerated for more than 50 cycles without a significant decrease in the luminescent properties and binding affinity of the sensing phase.4021032533260Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Spanish Ministry of EducationMinistry of Science and Innovation [PHB2005-0030-PC, CTQ2009-14565-C03]Complutense University [GR58-08-910072]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES [CAPES/DGU 125/06]Ministry of Science and Innovation [PHB2005-0030-PC, CTQ2009-14565-C03]Complutense University [GR58-08-910072

Analysis of alternariol and alternariol monomethyl ether in foodstuffs by molecularly imprinted solid-phase extraction and ultra-high-performance liquid chromatography tandem mass spectrometry

Molecularly imprinted porous polymer microspheres selective to Alternaria mycotoxins, alternariol (AOH) and alternariol monomethyl ether (AME), were synthesized and applied to the extraction of both mycotoxins in food samples. The polymer was prepared using 4-vinylpiridine (VIPY) and methacrylamide (MAM) as functional monomers, ethylene glycol dimethacrylate (EDMA) as cross-linker and 3,8,9-trihydroxy-6H-dibenzo[b, d] pyran-6- one (S2) as AOH surrogate template. A molecularly imprinted solid phase extraction (MISPE) method has been optimized for the selective isolation of the mycotoxins from aqueous samples coupled to HPLC with fluorescence (lambda(ex)= 258 nm;lambda(em) = 440 nm) or MS/MS analysis. The MISPE method was validated by UPLC-MS/MS for the determination of AOH and AME in tomato juice and sesame oil based on the European Commission Decision 2002/657/EC. Method performance was satisfactory with recoveries from 92.5% to 106.2% and limits of quantification within the 1.1-2.8 mu g kg(-1) range in both samples

Nanoscopic optical sensors based on functional supramolecular hybrid materials

[EN] This review highlights how the combination of supramolecular principles and nanoscopic solid structures enables the design of new hybrid sensing ensembles with improved sensitivity and/or selectivity and for the targeting of analytes for which selectivity is hard to achieve by conventional methods. Such ideas are bridging the gap between molecules, materials sciences and nanotechnology. Relevant examples will be detailed, taking into account functional aspects such as (1) enhanced coordination of functionalized solids, (2) enhanced signalling through preorganization, (3) signalling by assembly-disassembly of nanoscopic objects, (4) biomimetic probes utilizing discrimination by polarity and size and (5) distinct switching and gating protocols. 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A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

<p>Abstract</p> <p>Growing consumer interest in grass-fed beef products has raised a number of questions with regard to the perceived differences in nutritional quality between grass-fed and grain-fed cattle. Research spanning three decades suggests that grass-based diets can significantly improve the fatty acid (FA) composition and antioxidant content of beef, albeit with variable impacts on overall palatability. Grass-based diets have been shown to enhance total conjugated linoleic acid (CLA) (C18:2) isomers, <it>trans </it>vaccenic acid (TVA) (C18:1 t11), a precursor to CLA, and omega-3 (n-3) FAs on a g/g fat basis. While the overall concentration of total SFAs is not different between feeding regimens, grass-finished beef tends toward a higher proportion of cholesterol neutral stearic FA (C18:0), and less cholesterol-elevating SFAs such as myristic (C14:0) and palmitic (C16:0) FAs. Several studies suggest that grass-based diets elevate precursors for Vitamin A and E, as well as cancer fighting antioxidants such as glutathione (GT) and superoxide dismutase (SOD) activity as compared to grain-fed contemporaries. Fat conscious consumers will also prefer the overall lower fat content of a grass-fed beef product. However, consumers should be aware that the differences in FA content will also give grass-fed beef a distinct grass flavor and unique cooking qualities that should be considered when making the transition from grain-fed beef. In addition, the fat from grass-finished beef may have a yellowish appearance from the elevated carotenoid content (precursor to Vitamin A). It is also noted that grain-fed beef consumers may achieve similar intakes of both n-3 and CLA through the consumption of higher fat grain-fed portions.</p