Prediction of partition coefficients using COSMO-RS: Solvent screening for maximum conversion in biocatalytic two-phase reaction systems

Many biocatalytic reaction systems are biphasic with a reactive and an immiscible non-reactive phase. The reactive, mostly aqueous phase provides a natural enzyme environment and the non-reactive phase serves for delivery of dissolved substrates at high concentrations and for extraction of products. The proper choice of the non-reactive phase will have manifold influence on the catalytic parameters, such as activity, selectivity, and stability, but also on the maximum obtainable conversion or yield.

Conversion or yield constitutes a concise target of practical relevance for rational solvent screening which requires thermodynamic information on coupled reaction and phase equilibria as input information. As long as the reactive phase is kept constant, only the partition equilibrium of each solute in any solvent combination has to be determined. The experimental determination of these data requires a considerable laboratory effort. Therefore, an in-silico screening of solvents for maximal conversion of alcohol dehydrogenase-catalysed oxidoreductions of prochiral ketones was evaluated. COSMO-RS was used for the prediction of solute partitioning between organic solvents and aqueous reaction medium.

Although significant absolute deviations were found, COSMO-RS still predicted the correct trends for the partition coefficients of solutes in different solvents. The calculated overall reaction equilibrium using these partition coefficients again resulted in the prediction of the correct best solvent regarding conversion.     

Potential dependent adsorption behaviour of thiothymine derivatives on the Au(1 1 1) electrode

The adsorption behaviour of 2-thiothymine and 4-thiothymine on a Au(1 1 1) single crystal electrode has been studied using cyclic voltammetry and X-ray photo electron spectroscopy. For both thio derivatives the adsorption region is restricted due to the onset of reversible oxidization to 2,2′-bis(1H-5-methylpyrimidin-4-one-2-yl)-disulphide or 4,4′-bis(1H-5-methylpyrimidin-2-one-4-yl)-disulphide at anodic potentials. Two different orientations of adsorbed 2-thiothymine have been observed. Between −350 mV and −700 mV versus Ag/Ag⁺ the molecule is solely chemisorbed via its sulphur atom and adopts an upright orientation towards the surface. However at more negative potentials 2-thiothymine is reoriented into a slightly tilted position interacting via its S, N and O atoms with the surface. In contrast, 4-thiothymine exhibits only one adsorption geometry. Between −300 mV and −700 mV versus Ag/Ag⁺ it is chemisorbed via sulphur and nitrogen adopting a slightly tilted position. At −950 mV versus Ag/Ag⁺ 4-thiothymine is irreversibly reduced. The sulphur substituent is eliminated and covers the substrate.     

Speech errors, phonotactic constraints, and implicit learning: A study of the role of experience in language production.

Speech errors follow the phonotactics of the language being spoken. For example, in English, if [n] is mispronounced as [ ], the [ ] will always appear in a syllable coda. The authors created an analogue to this phenomenon by having participants recite lists of consonant–vowel–consonant syllables in 4 sessions on different days. In the first 2 experiments, some consonants were always onsets, some were always codas, and some could be both. In a third experiment, the set of possible onsets and codas depended on vowel identity. In all 3 studies, the production errors that occurred respected the "phonotactics" of the experiment. The results illustrate the implicit learning of the sequential constraints present in the stimuli and show that the language production system adapts to recent experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Versatile Transport Network for Sequestering and Excreting Plant Glycosides in Leaf Beetles Provides an Evolutionary Flexible Defense Strategy

The larval defenses of chrysomeline leaf beetles comprise components that are either synthesized de novo or sequestered from their food plants. Both biosynthetic modes are based on glucosides that serve as substrates and forms of transport. The defensive glands import the compounds through highly selective glucoside transporters from a circulating pool in the hemolymph. Here we address the selectivity of the different transport systems with larvae of Chrysomela populi, an obligate sequestering species, and with larvae of Phaedon cochleariae, producing nonaterpene iridoids. Both species possess an interconnected network of transport systems for uptake and excretion. The glucosides are imported by the gut membrane with low selectivity. Their excretion by the Malpighian tubules is similarly unselective, but the uptake of the glucosides from the hemolymph into the defensive system is specific. Only the genuine glucoside precursors made de novo or sequestered from the plant are imported. The successful combination of the precursor‐adapted pathways of excretion and defense has probably allowed many leaf beetle species to adaptively radiate onto, and coevolve with plants that offer appropriate glucoside precursors.     

On the fractal character of polymer spherulites: an ultra‐small‐angle X‐ray scattering study of poly[(R)‐3‐hydroxybutyrate]

Ultra‐small‐angle X‐ray scattering (USAXS) and small‐angle X‐ray scattering (SAXS) measurements are presented for poly[(R)‐3‐hydroxybutyrate] (PHB) crystallized at room temperature. The USAXS patterns indicated that the spherulites had a radially orientated fibrillar nanostructure with fractal geometry over a length scale ranging from 12 nm up to at least 300 nm, with a mass fractal dimension of approximately 2.7 in aged samples. The SAXS patterns indicated that the fibrils themselves were built up of bundles of crystalline lamellae separated by layers of disordered material, with a period length of approximately 6 nm. The SAXS measurements during primary crystallization gave an initial fractal dimension of 4 during spherulite growth, due to the sharp phase boundary between the spherulites and the melt. Copyright © 2004 Society of Chemical Industry     

Development of methods for encapsulation of viruses into polymeric nano‐ and microparticles for aquaculture vaccines

To meet an urgent need for improved vaccines against viral diseases in aquaculture, encapsulating the viruses into biodegradable and biocompatible polymers was suggested to protect viral antigens from premature degradation and gradually expose them to the immune system. We used water‐in‐oil‐in‐water emulsion to first encapsulate model red fluorescent polystyrene (PS) particles and then infectious salmon anemia virus (ISAV) into poly‐lactic‐co‐glycolic acid (PLGA) together with coumarin 6. A milder layer‐by‐layer method was applied to incorporate both PS and ISAV into chitosan (Cs)‐fluorescein isothiocyanate and alginate (Alg) followed by ionic crosslinking. All particles were characterized by dynamic light scattering, zeta‐sizer, fluorescence, transmission‐ and scanning electron microscopy. Successful encapsulation of PS beads and ISAV into PLGA, Cs, and Alg was accomplished. The prepared particles were of different size, surface charge density, and morphology. This yields opportunities for further developments of these structures as vaccine candidates to be delivered by injection or oral administration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40714.     

Polymerbasierte sphärische Aktivkohlen in Kombination mit TS‐1 als effiziente Epoxidierungskatalysatoren

The heterogeneously catalyzed epoxidation of commercial biodiesel with aqueous H₂O₂ as oxidizing agent has been studied using composite catalysts composed of microporous titanium silicalite (TS‐1) as a reactive, and a polymer‐based spherical activated carbon as sorptive functionality. The results were compared with the performance of a commercial TS‐1 catalyst. The polymer‐based spherical activated carbon was used either as a support or as exotemplate. The efficiency of the active titanium sites was four times higher in the composite catalyst than in the commercial TS‐1 catalyst.     

Proteome Characterization of BALF Extracellular Vesicles in Idiopathic Pulmonary Fibrosis: Unveiling Undercover Molecular Pathways

In the longtime challenge of identifying specific, easily detectable and reliable biomarkers of IPF, BALF proteomics is providing interesting new insights into its pathogenesis. To the best of our knowledge, the present study is the first shotgun proteomic investigation of EVs isolated from BALF of IPF patients. Our main aim was to characterize the proteome of the vesicular component of BALF and to explore its individual impact on the pathogenesis of IPF. To this purpose, ultracentrifugation was chosen as the EVs isolation technique, and their purification was assessed by TEM, 2DE and LC-MS/MS. Our 2DE data and scatter plots showed considerable differences between the proteome of EVs and that of whole BALF and of its fluid component. Analysis of protein content and protein functions evidenced that EV proteins are predominantly involved in cytoskeleton remodeling, adenosine signaling, adrenergic signaling, C-peptide signaling and lipid metabolism. Our findings may suggest a wider system involvement in the disease pathogenesis and support the importance of pre-fractioning of complex samples, such as BALF, in order to let low-abundant proteins-mediated pathways emerge.     

Dielectric relaxation spectroscopy of poly[(R)‐3‐hydroxybutyrate] (PHB) during crystallization

The dielectric response of poly [(R)‐3‐hydroxybutyrate] (PHB) was investigated as a function of time after quenching a film from the melt to a crystallization temperature of 20 °C. In the frequency range investigated (20 to 10⁶ Hz) a relaxation maximum was observed–attributable to the glass transition–which could be analysed by the Havriliak–Negami relation. Changes in the complex dielectric constant were monitored both during spherulite growth (primary crystallization) and subsequently during a period of progressive crystallization (secondary crystallization) at room temperature. The relaxation strength changed only slightly during primary crystallization and its peak position remained at a constant frequency. Subsequently a continuous decrease in relaxation strength occurred, indicating considerable changes in molecular mobility after spherulite growth had been completed. The results provide further evidence that molecular mobility in the amorphous regions decreases significantly with time, and that this would be the reason why PHB shows embrittlement on ageing at room temperature. Copyright © 2004 Society of Chemical Industry