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Four 2,5-bis(5-aryl-3-hexylthiophen-2-yl)thiazolo[5,4-d]thiazole derivatives have been synthesized and thoroughly characterized. The extended aromatic core of the molecules was designed to enhance the charge transport characteristics, and solubilizing hexyl side chains were introduced on the thiophene subunits to enable possible integration of these semiconducting small molecules in printable electronics. Complete elucidation of the chemical structures by detailed one-dimensional/two-dimensional NMR spectroscopy is described, providing interesting input for chemical shift prediction software as well, because limited experimental data on these types of compounds are currently available. Furthermore, theoretical calculations have assisted experimental observations--giving support for the chemical shift assignment and providing a springboard for future screening and predictions--demonstrating the benefits of a coordinated theoretical-experimental approach.

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In the field of plastic electronics, low band gap conjugated polymers like poly(thienylene vinylene) (PTV) and its derivatives are a promising class of materials that can be obtained with high molecular weight via the so-called dithiocarbamate precursor route. We have performed a joint experimental-theoretical study of the full NMR chemical shift assignment in a series of thiophene-based model compounds, which aims at (i) benchmarking the quantum-chemical calculations against experiments, (ii) identifying the signature of possible structural defects that can appear during the polymerization of PTV's, namely head-to-head and tail-to-tail defects, and (iii) defining a criterion regarding regioregularity.

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Novel hexyl-substituted bisthiophene compounds containing a thiazolothiazole(5,4-d) unit have been explored. The molecules are soluble in common organic solvents, which would enhance their chance of possible integration in printable electronics. Synthesis and complete elucidation of the chemical structures by detailed 1D/2D NMR spectroscopy are described. This provides interesting input for chemical shift prediction software, because few experimental data on this type of compounds are available. Furthermore, the potential n-type character of these derivatives is verified using electrochemical measurements. In addition, the low-bandgap character of conjugated polymers containing the thiazolothiazole unit is demonstrated by performing an electropolymerization.

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Mimicking the selectivity and sensitivity of biological systems for sensor devices is of increasing interest in biomedical, environmental and chemical analysis. Synthetic materials with imprinted nanocavities, acting as highly selective artificial receptors, are a tailor-made solution in obtaining such a sensor. Incorporation of such molecularly imprinted polymers (MIPs) in a platform suitable for electrochemical measurements, can offer high sensitivity together with device miniaturization and an electronic read-out. As a proof of principle, a MIP-based sensor for L-nicotine has been developed. To this end, the molecular structure of L-nicotine was imprinted in a polymer matrix of polymethacrylic acid (PMAA). Subsequently, microparticles of the imprinted polymer were immobilized on thin films of the conjugated polymer OC(1)C(10)-PPV. These films were incorporated in an impedimetric sensing device. Using electrochemical impedance spectroscopy, the real part of the impedance was monitored for various concentrations. This setup allows for the detection of l-nicotine from 1 to 10 nM and is insensitive for the resembling molecule L-cotinine.

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In our laboratory a precursor route to poly(p-phenylenevinylene) derivatives is developed in which unsymmetrically substituted p-xylene derivatives, possessing a benzylic sulfinylalkyl group, are used as monomers. Because of this unsymmetry, we were forced to investigate thoroughly the synthesis of these sulfoxides, as we start from symmetric and readily accessible molecules, namely, bis(halomethyl)-p-xylene derivatives. In a former publication, a new extremely effective route for the production of these unsymmetrically substituted sulfinyl monomers was presented. This paper expands upon these previously reported results. To examine the scope and limitations of this elegant route, this new method was applied to the synthesis of various derivatives not included in the initial work.

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The metabolism of the illegal growth promoter ethylestrenol (EES) was evaluated in bovine liver cells and subcellular fractions of bovine liver preparations. Incubations with bovine microsomal preparations revealed that EES is extensively biotransformed into norethandrolone (NE), another illegal growth promoter. Furthermore, incubations of monolayer cultures of hepatocytes with NE indicated that NE itself is rapidly reduced to 17alpha-ethyl-5beta-estrane-3alpha, 17beta-diol (EED). In vivo tests confirmed that, after administration of either EES or NE, EED is excreted as a major metabolite. Therefore, it was concluded that, both in urine and faeces samples, EED can be used as a biological marker for the illegal use of EES and/or NE. Moreover, by monitoring EED in urine or faeces samples, the detection period after NE administration is significantly prolonged. These findings were further confirmed by three cases of norethandrolone abuse in a routine screening program for forbidden growth promoters.

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In Belgium, to control the abuse of anabolic steroids in cattle, urine samples have been gradually replaced by feces samples, because the latter can be obtained more easily from living animals. Urine and feces samples were collected from heifers after administration of boldenone, norethandrolone or ethylestrenol. Metabolites present in feces or urine were determined by GC-MS. Large qualitative and quantitative differences in the metabolic profiles were observed. In feces, in contrast to urine, the parent compounds or their major metabolites were detectable only shortly after administration. On the other hand, metabolites resulting from the reduction of the 3-oxo group and the unsaturated carbon-carbon bonds, present on the A-ring, allow for long-term detection in feces. A-ring reduced metabolites have been identified in samples found positive for norgestrel, boldenone, methylboldenone and methyltestosterone, respectively. These results are in agreement with concomitant in vivo experiments.

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Current veterinary residue analysis mainly focuses on the monitoring of residues of the administered parent compound. However, it is possible that larger amounts of metabolites are excreted and that they can have a prolonged excretion period. In order to unravel specific metabolic steps and to identify possible biological markers, two in vitro liver models were used, i.e. monolayer cultures of isolated hepatocytes and liver microsomes, both prepared from liver tissue of cattle. Chostebol, boldenone, norethandrolone (NE) and ethylestrenol (EES) were used as model substrates. Results show that the metabolic profiles derived from in vitro experiments are predictive for the in vivo metabolic pathways of the steroids evaluated in this study. By means of this strategy, it is possible to identify 17 alpha-ethyl-5 beta-estrane-3 alpha,17 beta-diol (EED) as a common biological marker for NE and EES. By in vivo experiments it was shown that EED is particularly important for the detection of the abuse of NE or EES because of its high excretion levels and its prolonged presence as compared with the parent compounds or any other metabolite.

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17 alpha-Boldenone (17 alpha-BOL) and/or 17 beta-boldenone (17 beta-BOL) appear occasionally in fecal matter of cattle. In addition to 17 alpha-BOL, a whole array of boldenone related substances can be found in the same samples. In vitro experiments with microsomal liver preparations and isolated hepatocytes combined with the excretion profiles found in urine and feces samples of in vivo experiments made it possible to identify several metabolites of 17 beta-BOL in 17 beta-BOL positive feces samples. In one animal treated with 17 beta-BOL, no 17 beta-BOL or its metabolites were present before treatment and most of these compounds disappeared gradually in time after the treatment was stopped. It is not clear what the origin is of 17 alpha-BOL and boldenone metabolites in samples screened routinely for the abuse of anabolic steroids and considered to be 'negative' because of the absence of 17 beta-BOL since other workers showed some evidence that 17 alpha-BOL can be of endogenous origin. However, in our hands, most of these 17 alpha-BOL positive samples, obtained during routinely performed screenings of cattle, contained large amounts of delta 4-androstene-3,17-dione (AED), which normally is absent from routinely screened negative samples. Furthermore, AED was absent in all samples obtained from the animals treated with 17 beta-BOL. We have no direct evidence that 17 alpha-BOL or 17 beta-BOL is of endogenous origin.

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