Arsenic biomethylation by the microorganism apiotrichum humicola in the presence of l-methionine-methyl-d3

The microorganism Apiotrichum humicola (previously known as Candida humicola) grown in the presence of either arsenate, arsenite, methylarsonic acid or dimethylarsinic acid, produces arsenic-containing metabolites in the growth medium. When L-methionine-methyl-d₃ is added to the cultures, the CD₃ label is incorporated intact into the metabolites to a considerable extent to form deuterated dimethylarsenic and trimethyl-arsenic species, indicating that S-adenosylmethionine, or some related sulphonium compound, is involved in the biological methylation. Conclusive evidence of CD₃ incorporation in the arsenicals found in the growth medium was provided by using a specially developed hydride generation-gas chromatography-mass spectrometry system (HG–GC–MS).     

Immunosensor for estrone with an equal limit of detection as common analytical methods

Immunoanalytical methods at a very low limit of detection (LOD) and a low limit of quantification (LOQ) are becoming more and more important for environmental analysis and especially for monitoring drinking water quality. Biosensors have suitable characteristics such as efficiency in allowing very fast, sensitive, and cost-effective detection. Here we describe a fully automated immunoassay for estrone with a LOD below 0.20 ng L^–1 and a LOQ below 1.40 ng L^–1. In contrast to common analytical methods such as GC-MS or HPLC-MS, the biosensor used requires no sample pre-treatment and pre-concentration. The basis of our sensitive assay is the antibody with a high affinity constant towards estrone. The very low amount of antibody per sample results in low validation parameters (LOD, LOQ, and IC50), but this assay for estrone represents the current device-related limitation of the River Analyser (RIANA).     

Triphenylene silanes for direct surface anchoring in binary mixed self-assembled monolayers

New triphenylene-based silanes 2-(ω-(chlorodimethylsilyl)-n-alkyl)-3,6,7,10,11-penta-m-alkoxytriphenylene 4 (Tm-Cn) with n = 8 or 9 and m = 7, 8, 9, 10, or 11 were synthesized, and their self-assembly behavior in the liquid state and at glass and silicon oxide surfaces was investigated. The mesomorphic properties of triphenylene silanes 4 (Tm-Cn) and their precursors 3 (Tm-Cn) were determined by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. From the small-angle X-ray scattering (SAXS) regime, a preferential discotic lamellar mesophase can be deduced, and wide-angle X-ray scattering (WAXS) highlights the liquid-like characteristics of the alkyl side chains. To transfer these bulk structural properties to thin films, self-assembled monolayers (SAMs) were obtained by adsorption from solution and characterized by water contact angle measurements, null ellipsometry, and atomic force microscopy (AFM). Employing the concentration as an additional degree of freedom, binary SAMs of 2-(ω-(chlorodimethylsilyl)-undecyl)-3,6,7,10,11-penta-decyloxytriphenylene 4 (T10-C11) were coassembled with chlorodecyldimethylsilane or chlorodimethyloctadecylsilane, and their capability as model systems for organic templating was evaluated. The structure of the resulting binary mixed SAMs was analyzed by water contact angle measurements, null ellipsometry, and X-ray reflectivity (XRR) in combination with theoretical modeling by a multidimensional Parratt algorithm and AFM. The composition dependence of film thickness and roughness can be explained by a microscopic model including the steric hindrance of the respective molecular constituents.     

Thiol‐ene photopolymerization for efficient curing of vinyl esters

Monomers for radical photopolymerization based on vinyl esters (VEs) have recently been identified as suitable alternatives to (meth)acrylates on account of their low irritancy and cytotoxicity. The drawback of most VEs with abstractable hydrogens is their relatively low reactivity compared with (meth)acrylates. Within this article, we proved by photo‐differential scanning calorimetry measurements and real‐time Fourier transform infrared spectroscopy that the thiol‐ene concept is able to improve the photoreactivity of these VEs to a large extent to a level between those of acrylates and methacrylates. Other VEs have now a reactivity of at least the level of similar acrylates. Mechanical properties as determined by Dynamic Mechanical Analysis and Charpy impact tests showed significant toughening of these materials. Furthermore, we were able to confirm low toxicity of all components by osteoblast cell culture experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Cyclisierungen unter beteiligung von fluoridionen. 2. Mitteil. [1], [2]. 4.5-perfluor-1.3-dioxolane

4.5-Perfluoro-1.3-dioxolanes $\text{2}$ are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides $\text{3}$ or -ketone $\text{9}$ with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in $\text{2}$ can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives $\text{16}$ the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes $\text{18}$ are formed by reaction with triethylamine- hydrofluoride.     

Singularity in the thermal boundary resistance between superfluid (4)He and a solid surface

We report new measurements in four cells of the thermal boundary resistance R between copper and (4)He below but near the superfluid-transition temperature T(lambda). For 10(-7)< or =t identical to 1-T/T(lambda))< or =10(-4) fits of R = R(0)t(-x(b))+R(B) to the data yielded x(b) approximately equal to 0.18, whereas a fit to theoretical values based on the renormalization-group theory yielded x(b) = 0.23. Alternatively, a good fit of the theory to the data could be obtained if the amplitude of the prediction was reduced by a factor close to 2. The results raise the question whether the boundary conditions used in the theory should be modified.     

Reorientation of the large-scale circulation in turbulent Rayleigh-Bénard convection

We present measurements of the orientation theta0(t) of the large-scale circulation (LSC) of turbulent Rayleigh-Bénard convection in cylindrical cells of aspect ratio 1. Theta0(t) undergoes irregular reorientations. It contains reorientation events by rotation through angles delta theta with a monotonically decreasing probability distribution p(delta theta), and by cessations (where the LSC stops temporarily) with a uniform p(delta theta). Reorientations have Poissonian statistics in time. The amplitude of the LSC and the magnitude of the azimuthal rotation rate have a negative correlation.