Azo‐group labelled polyesters by end‐capping with 2‐oxazoline derivatives – photochemical properties

Two azobenzene containing 2‐oxazolines were used for labeling of a polyester with carboxylic end groups by the end‐capping method. The modification was performed under the conditions of either reactive processing or in a solution. Photochemical activity of the prepared polymers, as well as that of the modifiers was studied. The polymers prepared represent new photosensitive materials that undergo photochemical trans‐cis isomerizations and reverse cis‐trans reactions.     

Bis-(bis-(1,3-diaminopropane)-copper(II) Tetracyanonickellate(II)) Tetrahydrate: Preparation, Characterization, and Crystal Structure of a Novel Molecular Tetracyanonickellate

Summary.  [Cu(tn)₂Ni(CN)₄]₂ċ4H₂O and Cu(tn)₂Ni(CN)₄ (tn = 1,3-diaminopropane) were prepared and characterized. The hydrate is unstable on air and readily dehydrates to Cu(tn)₂Ni(CN)₄. Crystal structure analysis of the hydrate at 150 K revealed a novel tetranuclear molecular structure of the tetracyanonickellate. The building elements are two [Cu(tn)₂]²⁺ cations (coordination numbers of Cu: 5 and 6, respectively), two [Ni(CN)₄)²⁻ anions, and crystal water. The two cations are linked by one tetracyanonickellate anion via bridging cyano groups placed in cis positions. The second anion is bound weakly (Cu-N = 2.82 ?) via one μ₂-bridging cyano ligand. The tetranuclear molecules and pairs of solvate water molecules are linked by strong hydrogen bonds, thus forming infinite planes which are linked in the third dimension by considerably weaker hydrogen bonds. Received May 9, 2000. Accepted (revised) August 21, 2000     

Biomaterials for molecular electronics development of optical biosensor for retinol

Molecular electronics involves expertise from several branches of science. Various biomaterials and electronics are involved in the fabrication of such devices. While passive biomaterials are involved in anchoring the active biomolecules, the latter are involved in switching and/or signal transduction. In the present investigation we have used a glass-capillary-based approach to design a biosensor for retinol. The sensing element is retinol-binding protein (RBP). The affinity of retinoic-acid-horseradish peroxidase (conjugate) to RBP is tested using a surface plasmon resonance technique. A simple photomultiplier-tube-based system is exploited to monitor the chemiluminescent signal generated upon reaction of hydrogen peroxide and luminol with the conjugate bound to RBP. The photomultiplier tube is directly coupled to a computer for data logging.     

Chemie und Verbrechen

Man has been under the spell of crime since the times of Kain and Abel, so why not put it to work in motivating chemistry students? Forensic work in the chemistry lab leads to a whole lot of interesting chemical principles and the students get acquainted with several advanced experimental methods.     

Comparison of 1D a 2D ITP-MS performance parameters and application possibilities: Ultratrace determination of B vitamins in human urine

The possibility to investigate analytes at ultra-low concentration levels still remains a hot topic in bioanalysis. In this area, various preconcentration techniques are an integral part of analytical procedures. When applying electromigration separation techniques, an isotachophoresis has been advantageously employed many times for this purpose. To solve current biomedical tasks effectively, an advanced two-dimensional isotachophoretic instrument (in a hydrodynamically closed separation system with an enhanced sample load capacity) hyphenated with mass spectrometry (ITP-ITP-MS) has been proposed by Foret and coworkers. As a continuation, this work represents the first study dealing with a full validation of an ITP-ITP-MS method. In order to see the benefits of an online ITP sample pretreatment (preconcentration and clean-up) on the performance parameters, the developed 2D ITP-MS method was compared with a corresponding 1D ITP-MS method. Application potentialities of the compared methods were demonstrated via a determination of two B vitamins, namely thiamine and pyridoxine, in human urine samples. The developed 2D ITP-MS method showed its enhanced effectivity and usefulness for a routine biomedical use (here, a reliable screening of trace B vitamins in human urine without an offline sample preparation).     

Fast and Sensitive Screening of Oxandrolone and Its Major Metabolite 17-Epi-Oxandrolone in Human Urine by UHPLC—MS/MS with On-Line SPE Sample Pretreatment

Oxandrolone, a synthetic testosterone analog, is used for the treatment of several diseases associated with weight loss. Unfortunately, oxandrolone is abused by many athletes and bodybuilders due to its strong anabolic effect. We have developed and validated a highly sensitive and rapid on-line SPE-UHPLC-MS/MS method for the determination of oxandrolone and simultaneous identification of its major metabolite 17-epi-oxandrolone in urine matrices. Enrichment of the analytes via an integrated solid-phase extraction was achieved using an Acquity UPLC BEH C18 Column. Subsequently, the chromatographic separation of the on-line preconcentrated sample fraction was achieved using an Acquity HSS T3 C18 Column. For the structural identification of these analytes, a high-resolution mass spectrometer Synapt-G2Si coupled to the Acquity M-class nano-LC system with ionKey source was used. A highly sensitive determination of oxandrolone was achieved using a tandem quadrupole mass spectrometer XEVO TQD. The method was successfully validated in the linear range of oxandrolone from 81.63 pg·mL⁻¹ (limit of quantification, LOQ) to 5000 pg·mL⁻¹ in the human urine matrix. It was applied to the analysis of real urine samples obtained from a healthy volunteer after the oral administration of one dose (10 mg) of oxandrolone. Concentration vs. time dependence was tested in the time interval of 4 h–12 days (after oral administration) to demonstrate the ability of the method to detect the renal elimination of oxandrolone from the human body. Favorable performance parameters along with successful application indicate the usefulness of the proposed method for its routine use in antidoping control labs.     

Diastereoselective Double C−H Functionalization of Chiral Ferrocenes with Heteroaromatics

Diastereoselective double C−H heteroarylation of chiral ferrocenes provides valuable compounds with multiple functionalities using mild reaction conditions and simple reagents. Pd-Complexes with chiral mono-protected amino acids afforded corresponding heteroarylated ferrocenyl amines in good yields and high diastereomeric purities. In this way, a variety of indole, thiophene, pyrrole, or furan substituents were introduced to the ferrocene moiety. Furthermore, a range of relevant functional groups, for example ketone, ester, chloro, nitro, or silyl, are tolerated by this method. An alternative combination of amino acid and ferrocenyl amine configurations was leveraged to provide the complementary diastereomeric products. The products of C−H heteroarylation can be transformed into corresponding phosphines. Absolute configurations of CH-activation products were confirmed by the combination of X-ray crystallographic analysis and CD spectroscopy. ¹⁹F NMR kinetic study and DFT calculations provided insights into the reaction mechanism and reasons governing stereoinduction.     

Large scale extreme risk assessment using copulas: an application to drought events under climate change for Austria

Droughts pose a significant challenge to farmers, insurers as well as governments around the world and the situation is expected to worsen in the future due to climate change. We present a large scale drought risk assessment approach that can be used for current and future risk management purposes. Our suggested methodology is a combination of a large scale agricultural computational modelling -, extreme value-, as well as copula approach to upscale local crop yield risks to the national scale. We show that combining regional probabilistic estimates will significantly underestimate losses if the dependencies between regions during drought events are not taken explicitly into account. Among the many ways to use these results it is shown how it enables the assessment of current and future costs of subsidized drought insurance in Austria.