Transparent plasmonic nanocontainers protect organic fluorophores against photobleaching

Numerous research efforts are investigating the possibility of using light interactions with metallic nanoparticles to improve the fluorescence properties of nearby molecules. Few investigations have considered the encapsulation of molecules in metallic nanocavities. In this paper, we present the optical properties of new hybrid nanoparticles consisting of gold nanoshells and fluorescent organic dyes in their liquid cores. Microspectroscopy on single nanoparticle demonstrates that the extinction spectra are in good agreement with Mie's theory. Finite difference time domain (FDTD) calculations reveal that excitation and emission radiations are efficiently transmitted through the thin gold nanoshells. Thus, they can be considered as transparent plasmonic nanocontainers for photoactive cores. In agreement with FDTD calculations, measurements show that fluorophores encapsulated in gold nanoshells keep their brightness, but they show fluorescence lifetimes 1 order of magnitude shorter. As a salient consequence, the photoresistance of encapsulated organic dyes is also improved by an order of magnitude. This unusual ultraviolet photoresistance results from the reduced probability of triplet-singlet conversion that eventually exposes dyes to singlet oxygen photodegradation.     

Engineering an allosteric binding site for aminoglycosides into TEM1-β-Lactamase

Allosteric regulation of enzyme activity is a remarkable property of many biological catalysts. Up till now, engineering an allosteric regulation into native, unregulated enzymes has been achieved by the creation of hybrid proteins in which a natural receptor, whose conformation is controlled by ligand binding, is inserted into an enzyme structure. Here, we describe a monomeric enzyme, TEM1-β-lactamase, that features an allosteric aminoglycoside binding site created de novo by directed-evolution methods. β-Lactamases are highly efficient enzymes involved in the resistance of bacteria against β-lactam antibiotics, such as penicillin. Aminoglycosides constitute another class of antibiotics that prevent bacterial protein synthesis, and are neither substrates nor ligands of the native β-lactamases. Here we show that the engineered enzyme is regulated by the binding of kanamycin and other aminoglycosides. Kinetic and structural analyses indicate that the activation mechanism involves expulsion of an inhibitor that binds to an additional, fortuitous site on the engineered protein. These analyses also led to the defining of conditions that allowed an aminoglycoside to be detected at low concentration.     

Identification of recombinant equine growth hormone in horse plasma by LC-MS/MS: a confirmatory analysis in doping control

Equine growth hormone (eGH) has been available since 1998 as an approved drug (EquiGen-5, Bresagen) containing recombinant eGH (reGH). It is suspected of being illegally administered to racehorses in order to improve physical performance and to speed-up wound healing. Thus it may be considered a doping agent which would require a sensitive and reliable method of identification and confirmation in order to regulate its use in racehorses. reGH differs from the native eGH by an additional methionine at the N-terminal (met-eGH) and has never been unambiguously detected in any type of biological matrix at trace concentrations (1-10 microg/L). A plasma sample (4 mL) was treated with ammonium sulfate at the reGH isoelectric point and the pellet was purified by solid-phase extraction. Specific peptides were generated by trypsin digestion and analyzed by LC-MS/MS. The detection limit was 1 microg/L. The method was validated according to European Union regulation (DEC/2002/657/EC) and the Association of Official Racing Chemists (AORC) requirements. Furthermore, it was successfully applied to determining the plasma concentrations of reGH with time using linear ion trap mass analyzer. The presence of this prohibited hormone (reGH) was also successfully detected by triple quadrupole mass spectrometry up to 48 h postadministration of reGH to a horse. The present LC-MS/MS method is the first with adequate sensitivity and specificity for detection of reGH, rbGH, and endogenous eGH. Hence, an efficient analytical tool is proposed as a means to fulfilling the regulation of reGH abuse in the horse racing industry.     

Effect of the addition of modified mica on mechanical and durability properties of FRP composite materials for civil engineering

The durability of fiber reinforced polymer (FRP) composite materials in humid and harsh environments is an important consideration for acceptance of these materials in civil engineering applications. Reducing the moisture ingress may improve the durability of FRPs. The addition of modified inorganic powder, such as clay nanoparticles, may improve several important properties of polymers, such as barrier properties, fire retardancy, dimensional stability, and mechanical strength. The present work aims to evaluate the effect of the addition of modified mica on FRP properties used in civil engineering applications. To conduct this preliminary study, the following steps were taken: (1) prepare and characterize composites made from lab‐made modified mica, (2) determine the maximum water uptake, water absorption rate and coefficient of diffusion, (3) characterize the mechanical properties, and finally, (4) evaluate the UV resistance. The experimental results show that the use of nanoparticles leads to a decrease of the coefficient of diffusion of water and a significant increase of stiffness and UV resistance. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Development of q-PCR approaches to assess water quality: effects of cadmium on gene expression of the diatom Eolimna minima

This study was undertaken to develop molecular tools to assess water quality using diatoms as the biological model. Molecular approaches were designed following the development of a rapid and easy RNA extraction method suited to diatoms and the sequencing of genes involved in mitochondrial and photosystem metabolism. Secondly the impact of cadmium was evaluated at the genetic level by q-PCR on 9 genes of interest after exposure of Eolimna minima diatom populations cultured in suspension under controlled laboratory conditions. Their growth kinetics and Cd bioaccumulation were followed.Population growth rates revealed the high impact of Cd at 100 μg/L with total inhibition of growth. These results are linked to the high bioaccumulation values calculated after 14 days of exposure, 57.0 ± 6.3 μg Cd/g dw and 734.1 ± 70 μg Cd/g dw for exposures of 10 and 100 μg Cd/L respectively.Genetic responses revealed the impact of Cd on the mitochondrial metabolism and the chloroplast photosystem of E. minima exposed to 10 and 100 μg Cd/L with induction of cox1, 12S, d1 and psaA after 7 days of exposure for the concentration of 100 μg Cd/L and of nad5, d1 and psaA after 14 days of exposure for both conditions.This is the first reported use of q-PCR for the assessment of toxic pollution on benthic river diatoms. The results obtained presage interesting perspectives, but the techniques developed need to be optimized before the design of new water quality diagnosis tools for use on natural biofilms.     

Thermodynamic evaluation and optimization of Al–Gd, Al–Tb, Al–Dy, Al–Ho and Al–Er systems using a Modified Quasichemical Model for the liquid

The Al–Gd, Al–Tb, Al–Dy, Al–Ho and Al–Er (Al–heavy rare earths) binary systems have been systematically assessed and optimized based on the available experimental data and ab-initio data using the FactSage thermodynamic software. A systematic technique (reduced melting temperature proposed by Gschneidner) was used for estimating the Al–Tb phase diagram due to lack of experimental data. Optimized model parameters of the Gibbs energies for all phases which reproduced all the reliable experimental data to satisfaction have been obtained. The optimization procedure was biased by putting a strong emphasis on the observed trends in the thermodynamic properties of Al–RE phases. The Modified Quasichemical Model, which takes short-range ordering into account, is used for the liquid phase and the Compound Energy Formalism is used for the solid solutions in the binary systems. It is shown that the Modified Quasichemical Model used for the liquid alloys permits one to obtain entropies of mixing that are more reliable than that based on the Bragg–Williams random mixing model which does not take short-range ordering into account.     

Mixed interpretation and extensions of the equivalent mass matrix approach for elastodynamics with contact

The present paper highlights the idea that the mass redistribution technique introduced by Khenous and co-workers (2006) [17], [18] for elastodynamics with impact, can be reinterpreted as a mixed formulation in displacements and velocities in which a special compatibility condition is enforced. Such a formulation opens the route to various extensions and to variational integrators for impact problems, potentially with variational time adaption. Those ideas are exemplified in the design of such integrators and various mass redistribution schemes.     

Nutritional modulation of gut microbiota in the context of obesity and insulin resistance: Potential interest of prebiotics

Obesity in humans leads to changes in the composition of gut microbiota, some of those changes being reversed upon dieting and changes in dietary habits. The studies devoted to understand how gut microbes control host energy homeostasis are of interest, in order to estimate how specific nutrients that induce changes in gut microbiota composition and/or activity – such as prebiotics – could be relevant in the management of obesity and related disorders. This review presents the potential molecular mechanisms allowing the gut microbiota to control host energy homeostasis, and presents the potential mechanisms evoked in the improvement of obesity by colonic nutrients that target the gut microbiota. It also discusses the relevance of this new area of research in human nutrition and health.     

EXPOSURE TO POLYCYCLIC AROMATIC HYDROCARBONS AND EXCRETION OF URINARY 3-HYDROXYBENZO[A]PYRENE: ASSESSMENT OF AN APPROPRIATE SAMPLING TIME

Biomonitoring of workers was carried out in seven workplaces—two aluminium plants, an electrometallurgy plant, two carbon brake disk factories, a creosoting workshop, and an artificial target factory—to assess exposure to polycyclic aromatic hydrocarbons (PAHs). At least all the 48 h voided urine samples were collected, the first urine before the preshift at the beginning of the week and the last one after the preshift of the third day. The 3-hydroxybenzo[a]pyrene (3-OHBaP) and 1-hydroxypyrene (1-OHPy) in each urine sample were then analyzed separately by methods developed by INRS. Concentration profiles were determined. They indicate a considerable lag between the maximum excretion of the two metabolites. Including the previously published data obtained with workers exposed to PAHs, this varies from 3 to 24 h (mean lag = 15 h, n = 42). In order to determine the most appropriate sampling time for 3-OHBaP, the time of the 3-OHBaP maximum concentration is compared with the preshift.