Biometallorganische Chemie: Ein faszinierendes Forschungsgebiet

Bioorganometallic Chemistry is a new research area in which organometallic compounds are coupled with biomolecules (sugars, peptides, DNA and its constituents, steroides, vitamines, enzymes). In a narrow sense such organometallic complexes occur in nature (vitamin B₁₂), have a biological function (e.g. nickel enzymes in bacterias) or are of potential medical use (as novel drug or as marker for biomolecules). In a wider sense bioorganometallic chemistry includes simply metal complexes which besides organometallic ligands (e.g. CO, π‐hydrocarbon) have a biomolecule as ligand (e.g. with interesting structures, for catalysis).     

Design,Synthesis, and In Vivo Evaluation of C1-Linked 4,5-Epoxymorphinan Haptens for Heroin Vaccines

In our continuing effort to develop effective anti-heroin vaccines as potential medications for the treatment of opioid use disorder, herein we present the design and synthesis of the haptens: 1-AmidoMorHap (1), 1-AmidoMorHap epimer (2), 1 Amido-DihydroMorHap (3), and 1 Amido-DihydroMorHap epimer (4). This is the first report of hydrolytically stable haptenic surrogates of heroin with the attachment site at the C1 position in the 4,5-epoxymorophinan nucleus. We prepared respective tetanus toxoid (TT)–hapten conjugates as heroin vaccine immunogens and evaluated their efficacy in vivo. We showed that all TT–hapten conjugates induced high antibody endpoint titers against the targets but only haptens 2 and 3 can induce protective effects against heroin in vivo. The epimeric analogues of these haptens, 1 and 4, failed to protect mice from the effects of heroin. We also showed that the in vivo efficacy is consistent with the results of the in vitro drug sequestration assay. Attachment of the linker at the C1 position induced antibodies with weak binding to the target drugs. Only TT-2 and TT-3 yielded antibodies that bound heroin and 6-acetyl morphine. None of the TT–hapten conjugates induced antibodies that cross-reacted with morphine, methadone, naloxone, or naltrexone, and only TT-3 interacted weakly with buprenorphine, and that subtle structural difference, especially at the C6 position, can vastly alter the specificity of the induced antibodies. This study is an important contribution in the field of vaccine development against small-molecule targets, providing proof that the chirality at C6 in these epoxymorphinans is a vital key to their effectiveness.     

Electrocoagulation of waterborne polymers in the presence of carbon black

Electrodeposition of paint is an electrochemical process, starting from water-borne polymers. The electrode reactions are water decomposition, leading to diffusion layers of an extreme pH. Coagulation of polymers proceeds in these layers as an acid / base reaction rather than as a direct discharge of macroions at the electrodes. The electrodeposited film behaves like a weak acid or alkaline ion exchanger. Under polarization, high electric field strength leads to charge separation and the formation of a double space charge. Current / voltage-behavior is nonlinear. The mechanism of charge transport is purely ionic. Resistivities are in the order of p = 10⁸ Ohm·cm in the wet film. The stoved film is an insulator. Electrodeposition of a second film is impossible. However, electrodeposition of the primary film in the presence of dispersed carbon black, studied in detail for the first time, leads to an appreciable electronic conductivity in the stoved film. ρ is in the order of 10⁵ - 10⁷ Ohm·cm even with a carbon black concentration of only a few wt.-%. This has been explained in terms of a stick percolation model and the preferential formation of transversal carbon black chains in the film. The relatively high resistivities found along these chains is due to the need of electron tunneling through ultrathin polymer films around the polymer wetted individual carbon black particles. Temperature behavior of resistivities, field effect and other proofs are given for this model. For practical application, the most important findung is the possibility of an electrodeposition of a coherent second layer and even of multilayers in the presence of only 1 - 5 wt.-% of an appropriate carbon black filler.     

Sol-Gel Synthesis of Nano-Scaled BaTiO3, BaZrO3 and BaTi0.5Zr0.5O3 Oxides via Single-Source Alkoxide Precursors and Semi-Alkoxide Routes

Sol-gel synthesis of nano-sized BaTiO₃, BaZrO₃ and BaTi_0.5Zr_0.5O₃ ceramics using alkoxide and semi-alkoxide routes has been investigated and the pervoskites obtained have been compared with respect to crystallisation temperature, crystallite size and compositional purity. Heterometal alkoxides containing two (for BaTiO₃ and BaZrO₃) and three (for BaTi_0.5Zr_0.5O₃) different metals were used as single-source precursors in the alkoxide route while semi-alkoxide synthesis was performed by reacting barium hydroxide or acetate with Ti and/or Zr alkoxides. Semi-alkoxide synthesis also produces stoichiometric and phase-pure oxides, however, at temperatures higher than 1000°C. At temperatures below 1000°C, BaCO₃ and small amounts of other undesired phases (e.g., BaTi₂O₄) were present in the oxides derived from semi-alkoxide synthesis. Thermal behaviour, studied by TGA/DTA measurements, shows that thermal decomposition occurs in three major steps and depends on the educt composition and the synthesis route. Among alkoxide derived powders, crystalline BaTi_0.5Zr_0.5O₃ phase is formed at 400°C while complete crystallisation of BaMO₃ ceramics occurs around 600°C. The cubic to tetragonal phase transition for BaTiO₃ is clearly observed at relatively low-temperature of 800°C. The stoichiometry and phase homogeneity of the obtained powders were demonstrated by energy dispersive X-ray analysis and powder diffractometry. The averaged crystallite size of the obtained nano-ceramics was evaluated using the FormFit programme. SEM and TEM observations revealed a high microstructural uniformity.     

Positron–neutrino correlations in 32Ar and 33Ar decays: Probes of scalar weak currents and nuclear isospin mixing

The positron–neutrino correlation in the 0⁺→0⁺ β-decay of ³²Ar was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of the narrow proton group following the super-allowed decay. Our result is consistent with the standard model prediction;for vanishing Fierz interference we find a=0.9989±0.0052±0.0039. Our result leads to improved constraints on scalar weak interactions. The positron–neutrino correlation in ³³Ar decay was measured in the same experiment;for vanishing Fierz interference we find a=0.944±0.002±0.003. The ³²Ar and ³³Ar correlations, in combination with precision measurements of the half-lives, super-allowed branching ratios and beta endpoint energies, will determine the isospin impurities of the super-allowed transitions. These will provide useful tests of isospin-violation corrections used in deducing |V_ud| which currently indicates non-unitarity of the KM matrix. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Torsion Function of Convex Domains of High Eccentricity

Potential Analysis - The torsion function of a convex planar domain Ω has convex level sets, but explicit formulae are known only for rectangles and ellipses. Here we study the torsion...     

Evaluation of double-tuned single-sided planar microcoils for the analysis of small 13C enriched biological samples using 1H-13C 2D heteronuclear correlation NMR spectroscopy

Microcoils provide a cost-effective approach to improve detection limits for mass-limited samples. Single-sided planar microcoils are advantageous in comparison to volume coils, in that the sample can simply be placed on top. However, the considerable drawback is that the RF field that is produced by the coil decreases with distance from the coil surface, which potentially limits more complex multi-pulse NMR pulse sequences. Unfortunately, ¹H NMR alone is not very informative for intact biological samples due to line broadening caused by magnetic susceptibility distortions, and ¹H-¹³C 2D NMR correlations are required to provide the additional spectral dispersion for metabolic assignments in vivo or in situ. To our knowledge, double-tuned single-sided microcoils have not been applied for the 2D ¹H-¹³C analysis of intact ¹³C enriched biological samples. Questions include the following: Can ¹H-¹³C 2D NMR be performed on single-sided planar microcoils? If so, do they still hold sensitivity advantages over conventional 5 mm NMR technology for mass limited samples? Here, 2D ¹H-¹³C HSQC, HMQC, and HETCOR variants were compared and then applied to ¹³C enriched broccoli seeds and Daphnia magna (water fleas). Compared to 5 mm NMR probes, the microcoils showed a sixfold improvement in mass sensitivity (albeit only for a small localized region) and allowed for the identification of metabolites in a single intact D. magna for the first time. Single-sided planar microcoils show practical benefit for ¹H-¹³C NMR of intact biological samples, if localized information within ~0.7 mm of the 1 mm I.D. planar microcoil surface is of specific interest.