The intrinsic fluorescence of FAD and its application in analytical chemistry: a review

This review (with 106 references) mainly deals with the analytical applications of flavin-adenine dinucleotide (FAD) fluorescence. In the first section, the spectroscopic properties of this compound are reviewed at the light of his different acid-base, oxidation and structural forms; the chemical and spectroscopic properties of flavin mononucleotide (FMN) and other flavins will be also briefly discussed. The second section discusses how the properties of FAD fluorescence changes in flavoenzymes (FvEs), again considering the different chemical and structural forms; the glucose oxidase (GOx) and the choline oxidase (ChOx) cases will be commented. Since almost certainly the most reported analytical application of FAD fluorescence is as an auto-indicator in enzymatic methods catalysed by FvE oxidoreductases, it is important to know how the concentrations of the different forms of FAD changes along the reaction and, consequently, the fluorescence and the analytical signals. An approach to do this will be presented in section 3. The fourth part of the paper compiles the analytical applications which have been reported until now based in these fluorescence properties. Finally, some suggestions about tentative future research are also given

Bmi1+ Progenitor Cell Dynamics in Murine Cornea During Homeostasis and Wound Healing

The outermost layer of the eye, the cornea, is renewed continuously throughout life. Stem cells of the corneal epithelium reside in the limbus at the corneal periphery and ensure homeostasis of the central epithelium. However, in young mice, homeostasis relies on cells located in the basal layer of the central corneal epithelium. Here, we first studied corneal growth during the transition from newborn to adult and assessed Keratin 19 (Krt19) expression as a hallmark of corneal maturation. Next, we set out to identify a novel marker of murine corneal epithelial progenitor cells before, during and after maturation, and we found that Bmi1 is expressed in the basal epithelium of the central cornea and limbus. Furthermore, we demonstrated that Bmi1+ cells participated in tissue replenishment in the central cornea. These Bmi1+ cells did not maintain homeostasis of the cornea for more than 3 months, reflecting their status as progenitor rather than stem cells. Finally, after injury, Bmi1+ cells fueled homeostatic maintenance, whereas wound closure occurred via epithelial reorganization. Stem Cells 2018

Evaluation of synthesis conditions for plastic scintillation foils used to measure alpha- and beta-emitting radionuclides

Plastic scintillation foils of polystyrene and polycarbonate with a thickness between 45 and 200 μm, have been produced using the solvent evaporation method. PSfoils presented a reproducible thickness (10-20%). PSfoils were characterized by the measurement of 36Cl or 241Am. For 36Cl spectrum is located at medium energies since not all energy is deposited in the scintillator and not all betas interact with the foils. For 241Am the efficiency values are very high and spectrum is a sharp peak located at high energies. 222Rn absorption (LD and K) and desorption capacities of the PSfoils have been also evaluated

Smartphone-interrogated test supports for the enzymatic determination of putrescine and cadaverine in food

Diamino-oxidase (DAO), horseradish peroxidase (HRP), and tetramethylbenzidine (TMB) have been immobilized into cellulose to obtain circular cellulose test supports (CCTSs) for the determination of cadaverine (Cad) and putrescine (Put). During the enzymatic reaction, TMB is oxidized and a blue spot is obtained. This color (RGB coordinates) is measured with a smartphone and a commercial application. The highest sensitivity is provided by the component R and a linear response is observed for low biogenic amine (BA) concentrations, but a second-order polynomial response better fits the experimental results for a wider concentration range. This has been successfully explained with a model developed to explain the RGB values obtained in this type of analytical system. Optimization studies enable CCTSs to be obtained for Put and Cad determination, which could be used (kept at 4 °C) for at least 45 days if a stabilizer (StabilCoat™ or StabilGuard™) is added during its synthesis. In these conditions, the R coordinate follows the model up to at least 4 × 10-4 M Put and/or Cad (both analytes give the same response). The method permits the Put and Cad determination from 5 × 10-5 M up to 4 × 10-4 M (RSD = 3%, n = 3). The CCTSs have been applied to Put + Cad determination in a tuna sample without any interference by other biogenic amines. The concentration found statistically agrees with that obtained using a HPLC-MS-validated method

A computerized analysis of the entire retinal ganglion cell population and its spatial distribution in adult rats

AbstractIn adult albino (SD) and pigmented (PVG) rats the entire population of retinal ganglion cells (RGCs) was quantified and their spatial distribution analyzed using a computerized technique. RGCs were back-labelled from the optic nerves (ON) or the superior colliculi (SCi) with Fluorogold (FG). Numbers of RGCs labelled from the ON [SD: 82,818±3,949, n=27; PVG: 89,241±3,576, n=6) were comparable to those labelled from the SCi [SD: 81,486±4,340, n=37; PVG: 87,229±3,199; n=59]. Detailed methodology to provide cell density information at small scales demonstrated the presence of a horizontal region in the dorsal retina with highest densities, resembling a visual streak

Scaling relations for implantation of size-selected Au, Ag, and Si clusters into graphite

The deposition of size-selected clusters represents a new route to the fabrication of truly nanometer-scale surface architectures, e.g., nanopores. We report a systematic experimental study, coupled with molecular dynamics simulations, of the implantation depths of size-selected Au7, Ag7, and Si7 clusters in the model graphite substrate. For impact energies between 1.0 and 5.5 keV, we find that the implantation depth scales linearly with the momentum of the clusters for all three types of cluster. This “universal” behavior is consistent with a (viscous) retarding force proportional to the velocity of the cluster, akin to Stokes’s law

Hydrolase–like catalysis and structural resolution of natural products by a metal–organic framework

The exact chemical structure of non–crystallising natural products is still one of the main challenges in Natural Sciences. Despite tremendous advances in total synthesis, the absolute structural determination of a myriad of natural products with very sensitive chemical functionalities remains undone. Here, we show that a metal–organic framework (MOF) with alcohol–containing arms and adsorbed water, enables selective hydrolysis of glycosyl bonds, supramolecular order with the so–formed chiral fragments and absolute determination of the organic structure by single–crystal X–ray crystallography in a single operation. This combined strategy based on a biomimetic, cheap, robust and multigram available solid catalyst opens the door to determine the absolute configuration of ketal compounds regardless degradation sensitiveness, and also to design extremely–mild metal–free solid–catalysed processes without formal acid protons.This work was supported by the Ministero dell’Istruzione, dell’Università e della Ricerca (Italy) and the MINECO (Spain) (Projects CTQ2016-75671-P, CTQ 2017-86735-P, RTC-2017-6331-5, Severo Ochoa program SEV-2016-0683 and Excellence Unit “Maria de Maeztu” MDM-2015-0538). R.B. thanks the MIUR (Project PON R&I FSE-FESR 2014–2020) for grant. L.B wishes to thank Italian MIUR for grant n. AIM1899391–1 in the framework of the project “Azione I.2, Mobilità dei Ricercatori, PON R&I 2014–2020”. Thanks are also extended to the “2019 Post-doctoral Junior Leader-Retaining Fellowship, la Caixa Foundation (ID100010434 and fellowship code LCF/BQ/PR19/11700011” (J. F.- S.). S. S.-N. thanks ITQ for the concession of a contract. D.A. acknowledges the financial support of the Fondazione CARIPLO/“Economia Circolare: ricerca per un futuro sostenibile” 2019, Project code: 2019–2090, MOCA. E.P. acknowledges the financial support of the European Research Council under the European Union’s Horizon 2020 research and innovation program/ERC Grant Agreement No. 814804, MOF-reactors

Remote sensing detection of nutrient uptake in vineyards using narrow-band hyperspectral imagery

This manuscript delves further into the assessment of narrow-band vegetation indices derived from hyperspectral imagery acquired at 1 m spatial resolution with the Compact Airborne Spectrographic Imager (CASI). Narrow-band indices proposed in this study were assessed as indicators of biochemical and structural parameters in Vitis vinifera L., observing their relationships with foliar variables such as N, P, K, Ca, Fe, Mg and chlorophyll a+b concentration (Ca+b). Hyperspectral indices were assessed to study their capability for vegetation condition monitoring as a function of fertilization treatments applied (basically extracts of Ascophyllum nodosum seaweed and chelates), showing associations with field variables. Narrow-band vegetation indices displayed sensitivity to vineyard growth and condition as a function of seaweed fertilization and other supplementary mineral correctors, such as chelates. This work shows the interest of using new narrow-band hyperspectral remote sensing indices for vineyard monitoring due to their potential to indicate physiological condition.