Aqueous Solution Chemistry of the Mo(3)PdS(4) Cube: Substitution Reactions and the Double to Single Cube Interconversion Induced by CO, Two Phosphines, Cl(-), Br(-), and NCS(-)

The kinetics of conversion of an edge-linked double cube, in this case [{Mo(3)PdS(4)(H(2)O)(9)}(2)](8+), to the corresponding single cube [Mo(3)(PdX)S(4)(H(2)O)(9)](4+), has been studied for the first time. Reaction is induced by six reagents X = CO, two water-soluble phosphines, Cl(-), Br(-), and NCS(-), which complex at the tetrahedral Pd. The first stage of reaction is fast and is accompanied by color changes, e.g. purple to dark blue in the case of Cl(-), assigned as double to single cube conversion. With X = CO and the two phosphines, when absorbance changes are intense enough for stopped-flow monitoring with reactants at Pd-SCN. On removal of e.g. Cl(-) by chromatography or addition of Ag(+), the double cube re-forms.     

Wasserstoffumlagerungen bei der elektronenstoßinduzierten Fragmentierung von Aminoäthern

Due to neighbouring group effects the behaviour under electron impact of amino ethers of the type RO(CH₂)_nNR₁R₂ is distinctly different from that of both simple ethers and amines. In addition to α-cleavages two further primary fragmentations can often be observed, one leading to [M–aldehyde]^+. or [M–ketone]^+. ions, the other (with n≥3) giving [M–R]⁺ ions. Both processes involve hydrogen rearrangements which were investigated by means of deuterium labelling. Their importance is strongly dependent upon the nature of the substituents R, R₁, R₂ and upon the length (n) of the carbon chain between the heteroatoms. This dependence can easily be explained by the fragmentation mechanisms put forward.     

Ultra-rapid separation of an angiotensin mixture in nanochannels using shear-driven chromatography

The present paper reports on the separation of a mixture of fluorescein isothiocyanate-labeled angiotensin I and II peptides in a shear-driven nanochannel with a C18-coating and using an eluent consisting of 5% acetonitrile in 0.02 M aqueous phosphate buffer at pH 6.5. The flat-rectangular nanochannel in fused silica consisted of an etched structure in combination with a flat moving wall. The very fast separation kinetics that can be achieved in a nanochannel allowed to separate the angiotensin peptides in less then 0.2 s in a distance of only 1.8 mm. Plate heights as small as 0.4 microm were calculated after substraction of the injection effect.     

Determination of acyclovir in horse plasma and body fluids by high-performance liquid chromatography combined with fluorescence detection and heated electrospray ionization tandem mass spectrometry

Two methods are presented for the determination of 'respectively' the plasma protein unbound and total concentration of acyclovir in horse plasma and body fluids: first, a liquid-liquid extraction was performed on plasma, combined with HPLC-fluorescence detection for the total plasma concentration; second a more sensitive method using high-performance liquid chromatography combined with heated electrospray ionization tandem mass spectrometry (LC-HESI-MS/MS) was described for plasma and for body fluids analysis. To obtain the unbound concentration of acyclovir in plasma, a simple deproteinization step using a Microcon filter was performed. Ganciclovir was used as an internal standard. Analysis was carried out on an Inertsil 5 ODS-3 column for the HPLC-fluorescence method. For the LC-HESI-MS/MS method a PLRP-S column was used. The limit of quantification (LOQ) for the total concentration was set at 50 and 2 ng mL(-1) for the HPLC-fluorescence method and the LC-HESI-MS/MS method, respectively. The limit of quantification for the unbound concentration was set at 5 ng mL(-1) and at 2 ng mL(-1) for body fluids. The methods were successfully used to perform pharmacokinetic and clinical studies in horses after intravenous and oral dosage of acyclovir and its prodrug valacyclovir.     

Effect of ionic liquid on dielectric, mechanical and dynamic mechanical properties of multi-walled carbon nanotubes/polychloroprene rubber composites

This paper focuses on the influence of ionic liquid on carbon nanotube based elastomeric composites. Multi-walled carbon nanotubes (MWCNTs) are modified using an ionic liquid at room temperature, 1-butyl 3-methyl imidazolium bis (trifluoromethylsulphonyl) imide (BMI) and modified MWCNTs exhibit physical (cation–π/π–π) interaction with BMI. The polychloroprene rubber (CR) composites are prepared using unmodified and BMI modified MWCNTs. The presence of BMI not only increases the alternating current (AC) electrical conductivity and polarisability of the composites but also improves the state of dispersion of the tubes as observed from dielectric spectroscopy and transmission electron microscopy respectively. In addition to the hydrodynamic reinforcement, the formation of improved filler–filler networks is reflected in the dynamic storage modulus (E′) for modified MWCNTs/CR composites in amplitude sweep measurement upon increasing the proportion of BMI. Hardness and mechanical properties are also studied for the composites as a function of BMI.     

Surface Modification of Poly-ε-Caprolactone with an Atmospheric Pressure Plasma Jet

In this work, poly-ε-caprolactone samples are modified by an atmospheric pressure plasma jet in pure argon and argon/water vapour mixtures. In a first part of the paper, the chemical species present in the plasma jet are identified by optical emission spectroscopy and it was found that plasmas generated in argon/0.05 % water vapour mixtures show the highest emission intensity of OH (A–X) at 308 nm. In a subsequent section, plasma jet surface treatments in argon and argon/water vapour mixtures have been investigated using contact angle measurements and X-ray photoelectron spectroscopy. The polymer samples modified with the plasma jet show a significant decrease in water contact angle due to the incorporation of oxygen-containing groups, such as C–O, C=O and O–C=O. The most efficient oxygen inclusion was however found when 0.05 % of water vapour is added to the argon feeding gas, which correlates with the highest intensity of OH (X) radicals. By optimizing the OH (X) radical yield in the plasma jet, the highest polymer modification efficiency can thus be obtained.     

Creating Space for Large Acceptors: Rational Biocatalyst Design for Resveratrol Glycosylation in an Aqueous System

Polyphenols display a number of interesting properties but their low solubility limits practical applications. In that respect, glycosylation offers a solution for which sucrose phosphorylase has been proposed as a cost‐effective biocatalyst. However, its activity on alternative acceptor substrates is too low for synthetic purposes and typically requires the addition of organic (co‐)solvents. Here, we describe the engineering of the enzyme from Thermoanaerobacterium thermosaccharolyticum to enable glycosylation of resveratrol as test case. Based on docking and modeling studies, an active‐site loop was predicted to hinder binding. Indeed, the unbolted loop variant R134A showed useful affinity for resveratrol (K_m=185 mM ) and could be used for the quantitative production of resveratrol 3‐α‐glucoside in an aqueous system. Improved activity was also shown for other acceptors, introducing variant R134A as promising new biocatalyst for glycosylation reactions on bulky phenolic acceptors.