An Expedient Synthesis of Flexible Nucleosides through Enzymatic Glycosylation of Proximal and Distal Fleximer Bases

The structurally unique “fleximer” nucleosides were originally designed to investigate how flexibility in a nucleobase could potentially affect receptor–ligand recognition and function. Recently they have been shown to have low-to-sub-micromolar levels of activity against a number of viruses, including coronaviruses, filoviruses, and flaviviruses. However, the synthesis of distal fleximers in particular has thus far been quite tedious and low yielding. As a potential solution to this issue, a series of proximal fleximer bases (flex-bases) has been successfully coupled to both ribose and 2′-deoxyribose sugars by using the N-deoxyribosyltransferase II of Lactobacillus leichmannii (LlNDT) and Escherichia coli purine nucleoside phosphorylase (PNP). To explore the range of this facile approach, transglycosylation experiments on a thieno-expanded tricyclic heterocyclic base, as well as several distal and proximal flex-bases were performed to determine whether the corresponding fleximer nucleosides could be obtained in this fashion, thus potentially significantly shortening the route to these biologically significant compounds. The results of those studies are reported herein.     

Comparisons of content and scientific quality indicators across peer-reviewed journal articles with more or less gender perspective: gender studies can do better

The field of gender studies has faced criticism for poor scholarship and methodology, both from within and outside academia. Here, we compare indicators of scientific quality across three samples of peer-reviewed journal articles with more, less and no gender perspective, on the assumption that gender studies tend to apply a gender perspective. The statements in the articles were content-analysed with respect to subject matter, their level of support in surrounding text, and other indicators of scientific quality. The higher the level of gender perspective, the lower was the scientific quality for seven out of nine indicators. Support was higher for the no gender perspective group, but did not differ across the two higher levels. We suggest that the impact of the field can be increased by implementing established research methods employed in other disciplines, especially in terms of bringing about desired social and societal change.     

Review on Dynamic Bandwidth Allocation of GPON and EPON

The passive optical network (PON) technology has been drastically improved in recent years. In spite of using the optical technology, the utilization of the entire bandwidth is a very challenging task. The main categories of PON are the Ethernet passive optical network (EPON) and gigabit passive optical network (GPON). These two networks use the dynamic bandwidth allocation (DBA) algorithm to attain the maximum usage of bandwidth, which is provided in the network dynamically according to the need of the customers with the support of the service level agreement (SLA). This paper will provide a clear review about the DBA algorithm of both technologies as well as the comparison.     

Influence of ethanol on the rennet-induced coagulation of milk

The influence of ethanol on the rennet-induced coagulation of milk was studied to investigate potential synergistic effects of these two mechanisms of destabilisation on the casein micelles. Addition of 5% (v/v) ethanol reduced the rennet coagulation time (RCT) of milk, whereas higher levels of ethanol (10-20%, v/v) progressively increased RCT. The temperature at which milk was coagulable by rennet decreased with increasing ethanol content of the milk. The primary stage of rennet coagulation, i.e., the enzymatic hydrolysis of kappa-casein, was progressively slowed with increasing ethanol content (5-20%, v/v), possibly due to ethanol-induced conformational changes in the enzyme molecule. The secondary stage of rennet coagulation, i.e., the aggregation of kappa-casein-depleted micelles, was enhanced in the presence of 5-15% ethanol, the effect being largest at 5% ethanol. Enhanced aggregation of micelles is probably due to an ethanol-induced decrease in inter-micellar steric repulsion. These results indicate an interrelationship between the effects of ethanol and chymosin on the casein micelles in milk, which may have interesting implications for properties of dairy products.     

Radiation doses to Norwegian heart-transplanted patients undergoing annual coronary angiography

Heart-transplanted patients in Norway undergo annual coronary angiography (CA). The aims of this study were to establish a conversion factor between dose-area product and effective dose for these examinations and to use this to evaluate the accumulated radiation dose and risks associated with annual CA. An experienced cardiac interventionist performed a simulated examination on an Alderson phantom loaded with thermoluminescence dosemeters. The simulated CA examination yielded a dose-area product of 17 Gy cm(2) and an effective dose of 3.4 mSv: the conversion factor between dose-area product and effective dose was 0.20 mSv Gy cm(-2). Dose-area product values from 200 heart-transplanted patients that had undergone 906 CA examinations between 2001 and 2008 were retrieved from the institutional database. Mean dose-area product from annual CA was 25 Gy cm(2), ranging from 2 to 140 Gy cm(2). Mean number of CA procedure was 8 (range, 1-23). Mean accumulated effective dose for Norwegian heart-transplanted patients between 2001 and 2008 was 34 mSv (range, 5-113 mSv). Doses and radiation risks for heart-transplanted patients are generally low, because most heart transplantations are performed on middle-aged patients with limited life expectancy. Special concern should however be taken to reduce doses for young heart-transplanted patients who are committed to lifelong follow-up of their transplanted heart.     

Micro structuration of gaas surface by wet etching: towards a specific surface behavior

Resonant microelectromechanical systems are promising devices for real time and highly sensitive measurements. The sensitivity of such sensors to additional mass loadings which can be increased thanks to the miniaturisation of devices is of prime importance for biological applications. The miniaturisation of structures passes through a photolithographic process and wet chemical etching. So, this paper presents new results on the anisotropic chemical etching of the gallium arsenide (GaAs) crystal used for this application, in several solutions. This paper focuses on the micro/nanostructuration of the sensing surface to increase the sensor sensitivity. Indeed, this active surface will be biofunctionalized to operate in biological liquid media in view of biomolecules detection. Several experimental conditions of etching bath composition, concentration and temperature were examined to obtain a large variety of geometrical surfaces topographies and roughness. According to the orientation dependence of the chemical etching process, the experiments were also performed on various GaAs crystal plates. The bath 1 H3PO4:9 H2O2:1 H2O appeared to be particularly adapted to the fabrication of the GaAs microstructured membrane: indeed, the bath is highly stable, anisotropic, and, as a function of temperature, it allows the production of a large variety of GaAs surface topographies.     

Synthesis and immunological properties of a tetrasaccharide portion of the B side chain of rhamnogalacturonan II (RG-II)

A highly convergent strategy was used for the synthesis of a tetrasaccharide [3-aminopropyl beta-L-arabinofuranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-alpha-L-arabinopyranoside] portion of the B side chain of the plant cell-wall pectic polysaccharide rhamnogalacturonan II (RG-II). The terminal nonreducing beta-L-arabinofuranosyl residue of the target compound was installed by using an arabinofuranosyl donor that was protected with a 3,5-O-(di-tert-butylsilane) group to facilitate nucleophilic attack from the beta-face. The synthetic strategy also employed a chemoselective glycosylation of a trichloroacetimidate donor with a thioglycosyl acceptor; this gave a product that could be used immediately in a subsequent glycosylation. The reducing end of the tetrasaccharide contained an aminopropyl group to facilitate conjugation to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA). Mice that were immunized with a KLH-tetrasaccharide conjugate produced antibodies that recognized RG-II isolated from Arabidopsis thaliana cell walls, but did not recognize RG-II obtained from red wine. Our data suggest that the arabinopyranosyl residue exists in the (4)C(1) conformation in the tetrasaccharide and in A. thaliana RG-II, whereas it has the (1)C(4) conformation in wine RG-II. It is proposed that differences in the conformation of side chain B might account for the ability of antibodies to discriminate between RG-II that was isolated from Arabidopsis and wine.     

UV radiation induces genome-mediated, site-specific cleavage in viral proteins

Much research has been dedicated to understanding the molecular basis of UV damage to biomolecules, yet many questions remain regarding the specific pathways involved. Here we describe a genome-mediated mechanism that causes site-specific virus protein cleavage upon UV irradiation. Bacteriophage MS2 was disinfected with 254 nm UV, and protein damage was characterized with ESI- and MALDI-based FT-ICR, Orbitrap, and TOF mass spectroscopy. Top-down mass spectrometry of the products identified the backbone cleavage site as Cys46-Ser47 in the virus capsid protein, a location of viral genome-protein interaction. The presence of viral RNA was essential to inducing backbone cleavage. The similar bacteriophage GA did not exhibit site-specific protein cleavage. Based on the major protein fragments identified by accurate mass analysis, a cleavage mechanism is proposed by radical formation. The mechanism involves initial oxidation of the Cys46 side chain followed by hydrogen atom abstraction from Ser47 C(α). Computational protein QM/MM studies confirmed the initial steps of the radical mechanism. Collectively, this study describes a rare incidence of genome-induced protein cleavage without the addition of sensitizers.     

Fungal pretreatment of wheat straw: Effects on the biodegradability of cell walls,structural polysaccharides,lignin and phenolic acids by rumen microorganisms

Disappearance of cell wall components of untreated straw and straw treated with the ligninolytic white-rot fungi Phanerochaete chrysosporium, Dichomitus squalens and Cyathus stercoreus were determined during the course of rumen digestion of samples in nylon bags. The first fungus degraded hemicelluloses and cellulose non-selectively, adversely affecting the digestion rate of crude cell walls. Dichomitus squalens and C. stercoreus preferentially degraded hemicelluloses and lignin, affording cell wall degradation rates 1.5 times higher than in native straw. Furthermore, the extent of cell wall digestion was also significantly enhanced. Both strains improved the extent of cellulose digestion, whereas the potentially degradable xylan fraction remained unchanged. Polysaccharide digestion rates were influenced in different ways depending on the strain tested: straw degraded by C. stercoreus showed an increase in cellulose digestion rate by 50%, whereas residual arabinose units were slowly degraded. Xylan was degraded 1.8 times faster in straw decayed' by D. squalens, while cellulose digestion remained unchanged. Phanerochaete chrysosporium depressed both xylan and cellulose digestion rates. Fungal-treated lignins were solubilised in the rumen faster than in untreated straw, whereas only treatment by C. stercoreus resulted in higher lignin losses. Esterified phenolic acids were extensively degraded by all three fungi. Residual ferulic and p-coumaric acids accumulated during rumen digestion, although only the former decreased in the original straw.