Unexpected Formation of a Doubly Bridged Cyclo-1,2-dithian 1D Coordination Cu<Subscript>2</Subscript>I<Subscript>2</Subscript>-Containing Luminescent Polymer

Abstract  

CuI reacts instantaneously with butanedithiol in MeCN solution to form a sparingly soluble and thermally stable colorless polymeric material 1 of composition [(Cu₂I₂){HS(CH₂)₄SH}] _n . Raman and IR spectroscopy confirm the presence of Cu(I) bound S–H functions. Furthermore, small amounts of the yellow compound [{Cu(μ₂-I)₂Cu}(C₄H₈S₂)₂] _n 2 co-crystallize after several days. If the reaction mixture is exposed to air, polymeric 2 is isolated as the main product. An X-ray diffraction study reveals that 1D polymer 2 is assembled by rhomboid Cu(μ₂-I)₂Cu clusters (d Cu···Cu 2.6843(18) ?), which are linked through the S-atoms of six-membered 1,2-dithian heterocycles, thus generating an infinite ribbon. The low-frequency region in the Raman spectra show a striking similarity suggesting that polymers 1 and 2 bear the same cluster rhomboid Cu(μ₂-I)₂Cu clusters. The photophysics and luminescence properties of 2 have been studied experimentally and by means of DFT/TDDFT calculations.     

A New SiF–Dipropargyl Glycerol Scaffold as a Versatile Prosthetic Group to Design Dimeric Radioligands: Synthesis of the [18F]BMPPSiF Tracer to Image Serotonin Receptors

A novel SiX–dipropargyl glycerol scaffold (X: H, F, or ¹⁸F) was developed as a versatile prosthetic group that provides technical advantages for the preparation of dimeric radioligands based on silicon fluoride acceptor pre‐ or post‐labeling with fluorine‐18. Rapid conjugation with the prosthetic group takes place in microwave‐assisted click conjugation under mild conditions. Thus, a bivalent homodimeric SiX–dipropargyl glycerol derivatized radioligand, [¹⁸F]BMPPSiF, with enhanced affinity was developed by using click conjugation. High uptake of the radioligand was demonstrated in 5‐HT_1A receptor‐rich regions in the brain with positron emission tomography. Molecular docking studies (rigid protein–flexible ligand) of BMPPSiF and known antagonists (WAY‐100635, MPPF, and MefWAY) with monomeric, dimeric, and multimeric 5‐HT_1A receptor models were performed, with the highest G score obtained for docked BMPPSiF: ?6.766 as compared with all three antagonists on the monomeric model. Multimeric induced‐fit docking was also performed to visualize the comparable mode of binding under in vivo conditions, and a notably improved G score of ?8.455 was observed for BMPPSiF. These data directly correlate the high binding potential of BMPPSiF with the bivalent binding mode obtained in the biological studies. The present study warrants wide application of the SiX–dipropargyl glycerol prosthetic group in the development of ligands for imaging with enhanced affinity markers for specific targeting based on peptides, nucleosides, and lipids.     

Biology-based modeling to analyze uranium toxicity data on Daphnia magna in a multigeneration study

Recent studies have investigated chronic toxicity of waterborne depleted uranium on the life cycle and physiology of Daphnia magna. In particular, a reduction in food assimilation was observed. Our aims here were to examine whether this reduction could fully account for observed effects on both growth and reproduction, for three successive generations, and to investigate through microscope analyses whether this reduction resulted from direct damage to the intestinal epithelium. We analyzed data obtained by exposing Daphnia magna to uranium over three successive generations. We used energy-based models, which are both able to fit simultaneously growth and reproduction and are biologically relevant. Two possible modes of action were compared - decrease in food assimilation rate and increase in maintenance costs. In our models, effects were related either to internal concentration or to exposure concentration. The model that fitted the data best represented a decrease in food assimilation related to exposure concentration. Furthermore, observations of consequent histological damage to the intestinal epithelium, together with uranium precipitates in the epithelial cells, supported the assumption that uranium has direct effects on the digestive tract. We were able to model the data in all generations and showed that sensitivity increased from one generation to the next, in particular through a significant increase of the intensity of effect, once the threshold for appearance of effects was exceeded.     

Variability and molecular typing of Streptococcus thermophilus strains displaying different proteolytic and acidifying properties

Proteolytic and acidifying properties of Streptococcus thermophilus strains isolated from yoghurt or cheeses were evaluated. Among 30 strains tested, 12 exhibited cell envelope-associated proteinase activity (PrtS⁺), three displayed a slight PrtS activity (PrtS^+/?) and 15 were PrtS^?, despite the presence of the corresponding gene (prtS) in eight of them. Sequencing of the prtS gene in four PrtS^? and one PrtS⁺ strains revealed that the absence of PrtS activity in the PrtS^? strain probably results from an alteration of the prtS regulation. The strains displaying the highest acidifying capacities were all PrtS⁺. All but one PrtS⁺ strains were phylogenetically close, as shown by the sequencing of their rDNA internal transcribed spacer (ITS) 16S-23S. More specifically, the high proteolytic and acidifying capacities are associated with the presence of a type II-ITS.     

Thermal decomposition of 4,4′-azobis(4-cyanopentanol)

Summary Several workers (Reed, 1971, 1972, Goldfein, 1975, Kartavykh, 1977) have employed the 4.4-azobis(4-cyanopentanol) (ACP) as the initiator for the radical polymerization of butadiene, isoprene or acrylic monomers. Nevertheless, the decomposition of (ACP) has never been studied, only the rate constant of decomposition (k_d) of (ACP) at 70 °C in acetone has been determined.The present paper reports the kinetics of the thermal decomposition of (ACP): the rate constant of decomposition (k_d) at various temperatures and the activation energy of decomposition are determined in dimethyl sulfoxide.     

Microelectrode biosensor for real-time measurement of ATP in biological tissue

The purines ATP, ADP, and adenosine are important extracellular signaling agents. Analysis of purinergic signaling has been slowed by lack of direct methods for measurement of purine release in real-time during physiological activity. We have previously reported microelectrode biosensors for adenosine, but similar sensors for ATP have remained elusive. We now describe an ATP biosensor formed by coating a Pt microelectrode with an ultrathin biolayer containing glycerol kinase and glycerol-3-phosphate oxidase. It responds rapidly (10-90% rise time <10 s) and exhibits a linear response to ATP over the physiologically relevant concentrations of 200 nM-50 microM and is very sensitive approximately 250 mA.M(-1).cm(-2). By including phosphocreatine kinase in the biolayer, we can optionally amplify the ATP signal and also make the sensor sensitive to external ADP. We have used our sensors to make the first demonstration that ATP is released from spinal networks in vivo during locomotor activity.     

99Tc- and 239Pu-Doped Glass Leaching Experiments: Residual Alteration Rate and Radionuclide Behavior

The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% ²³⁹PuO₂ (α emitter) and 0.24 wt% ⁹⁹TcO₂ (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH_90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer.     

Characterization and determination of brewer's solid wastes composition

Agro‐industrial wastes are produced in large quantities around the world from the processing and manufacturing of food and beverages. The disposal of these wastes into the environment leads to damage to ecosystems owing to their composition rich in organic matter. In this context it may be noted that the brewing industry, whose production process includes processing steps and fermentation of vegetable raw materials such as barley and/or other grains used as adjuncts and hops, generates various byproducts. The worldwide consumption of these beverages and the current model of breweries, which includes production on a large scale, lead to the generation of large amounts of brewery waste, namely spent grain, hot trub and residual yeast. Owing to its composition, these residues exhibit significant potential for application in bioprocess technologies. In this study the three residues mentioned had their composition determined as a function of moisture, ash, total organic carbon (TOC), total and soluble nitrogen, reducing sugar and soluble free amino nitrogen. Moreover, the residues were characterized for total acidity, pH and chemical oxygen demand (COD) of total and soluble fractions. The three residues evaluated had high moisture content (>80%) and high organic matter content (TOC and COD, ~50% and >1000 mg/g, respectively), which can highlights the significant protein fraction (almost 50% for hot trub and residual yeast), suggesting the possibility of using these wastes for recovery. Copyright © 2015 The Institute of Brewing & Distilling