Optical Extinction Spectroscopy of Oblate, Prolate and Ellipsoid Shaped Gold Nanoparticles: Experiments and Theory

Localized Surface Plasmons (LSP) on metallic nanoparticles of different shapes are investigated by extinction spectroscopy. Experimental results are compared to simulations by a Finite-Difference Time-Domain (FDTD) method. Three different shapes of nanoparticles are compared, oblates, prolates and ellipsoids, in terms of spectral tunability of the LSP resonance (LSPR). It is found that the complete geometry of the nanoparticle must be given to truly define the LSP resonance and that ellipsoids offer the widest spectral tunability.     

Large increases of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) on Sable Island, Nova Scotia, since 1995

Beach surveys for harp (Phoca groenlandica) and hooded (Cystophora cristata) seals documented a dramatic increase in their numbers on Sable Island in the mid-1990s. From late 1994 to 1998, 1,191 harp and 870 hooded seals, mostly young animals, were recorded on the island whereas, in the 1980s, no more than 5 animals of both species were observed each year. Of the 2,061 harp and hooded seals examined, 41.7% were found alive, 26.7% were killed by sharks, and 31.6% were found dead but intact. This increase in numbers of harp and hooded seals on Sable Island, which is south of their historic northern range, is consistent with the recent increase of extralimital occurrences of these species along the east coast of North America. However, the large number of seals recorded in this study provides more information on their demography than has previously been possible.     

Metabolomics analysis of liver reveals profile disruption in bovines upon steroid treatment

Introduction

The surveillance of illegal anabolic practices in bovine meat production is necessary to guarantee consumers’ health. Screening strategies based on the recognition of indirect biological effects are considered by the community as promising tools to overcome some limitations of classical analytical methods and might therefore concur to ensure safer food for the consumer.

Objectives

The present work aims at characterizing the metabolic profile induced in liver by administration of anabolic steroids, and at identifying potential disturbances in the hepatic metabolism.

Methods

A total of 32 liver samples, 16 from untreated bulls and 16 from bulls treated with an ear implant (Revalor-XS^®) containing trenbolone acetate (200 mg) and β-estradiol (40 mg), were analyzed following a LC–MS-based metabolomic analysis combining RP and HILIC chromatographic separations. Different multivariate statistical tools were applied to the datasets to select common metabolites that may be considered as potential markers based on their significant changes in concentrations after administration of sexual steroids.

Results

Eight candidate markers were identified. Moreover, a subset of four markers was also validated by a different laboratory that performed the same analysis using an independent instrumental and elaboration platform, confirming the robustness of the results achieved.

Conclusion

This study was performed mimicking experimental conditions that may be used during a potential misuse practice. It is promising in the objective of setting up an analytical strategy to highlight sexual steroids abuse in livestock animals.

     

Innovative integrated system for real-time measurement of hybridization and melting on standard format microarrays

Despite the great popularity and potential of microarrays, their use for research and clinical applications is still hampered by lengthy and costly design and optimization processes, mainly because the technology relies on the end point measurement of hybridization. Thus, the ability to monitor many hybridization events on a standard microarray slide in real time would greatly expand the use and benefit of this technology, as it would give access to better prediction of probe performance and improved optimization of hybridization parameters. Although real-time hybridization and thermal denaturation measurements have been reported, a complete walk-away system compatible with the standard format of microarrays is still unavailable. To address this issue, we have designed a biochip tool that combines a hybridization station with active mixing capability and temperature control together with a fluorescence reader in a single compact benchtop instrument. This integrated live hybridization machine (LHM) allows measuring in real time the hybridization of target DNA to thousands of probes simultaneously and provides excellent levels of detection and superior sequence discrimination. Here we show on an environmental single nucleotide polymorphism (SNP) model system that the LHM enables a variety of experiments unachievable with conventional biochip tools.     

Identification of new candidate pathogenicity factors in the xylem-invading pathogen Xanthomonas albilineans by transposon mutagenesis

Xanthomonas albilineans is a xylem-invading pathogen that produces the toxin albicidin that blocks chloroplast differentiation, resulting in disease symptoms of sugarcane leaf scald. In contrast to other xanthomonads, X. albilineans does not possess a hypersensitive response and pathogenicity type III secretion system and does not produce xanthan gum. Albicidin is the only previously known pathogenicity factor in X. albilineans, yet albicidin-deficient mutant strains are still able to efficiently colonize sugarcane. To identify additional host adaptation or pathogenicity factors, sugarcane 'CP80-1743' was inoculated with 1,216 independently derived Tn5 insertions in X. albilineans XaFL07-1 from Florida. Sixty-one Tn5 mutants were affected in development of leaf symptoms or in stalk colonization. The Tn5 insertion sites of these mutants were determined and the interrupted genes were identified using the recently available genomic DNA sequence of X. albilineans GPE PC73 from Guadeloupe. Several pathogenicity-related loci that were not previously reported in Xanthomonas spp. were identified, including loci encoding hypothetical proteins, a membrane fusion protein conferring resistance to novobiocin, transport proteins, TonB-dependent outer-membrane transporters, and an OmpA family outer-membrane protein.     

The effect of calcium ion on the urea denaturation of immobilized bovine trypsin

The effect of calcium ion on the urea denaturation of trypsin has been investigated. By using trypsin immobilized on glass beads, all possibilities of autolysis occurring during the denaturation process are eliminated. It was found that in 8 M urea calcium ion markedly decreases the denaturation rate of the immobilized trypsin. Conversely, the presence of calcium ion markedly accelerates the rate of renaturation of denatured immobilized trypsin. Calcium may exert its stabilizing effect on the tertiary structure of the protein by coordination to the side chains of Asp 194, Ser 190 and the carbonyl group of Ser 139 (using the chymotryptic numbering system).