Bestimmung von Cholesterin im Serum

Ohne Zusammenfassung     

A new specifically designed calix[8]arene for the synthesis of functionalized, nanometric and subnanometric Pd, Pt and Ru nanoparticles

A new thioester functionalized calix[8]arene derivative is used for the synthesis of metallic Pd, Pt and Ru nanoparticles, exhibiting several interesting features such as stability and remarkable surface functionalization. Crystalline particles of very small dimensions and good dispersion have been obtained.     

Molecular analysis of the kirromycin biosynthetic gene cluster revealed beta-alanine as precursor of the pyridone moiety

Kirromycin is a complex linear polyketide that acts as a protein biosynthesis inhibitor by binding to the bacterial elongation factor Tu. The kirromycin biosynthetic gene cluster was isolated from the producer, Streptomyces collinus Tü 365, and confirmed by targeted disruption of essential biosynthesis genes. Kirromycin is synthesized by a large hybrid polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) encoded by the genes kirAI-kirAVI. This complex involves some very unusual features, including the absence of internal acyltransferase (AT) domains in KirAI-KirAV, multiple split-ups of PKS modules on separate genes, and swapping in the domain organization. Interestingly, one PKS enzyme, KirAVI, contains internal AT domains. Based on in silico analysis, a route to pyridone formation involving PKS and NRPS steps was postulated. This hypothesis was experimentally proven by feeding studies with [U-13C3(15)N]beta-alanine and NMR and MS analyses of the isolated pure kirromycin.     

Analysis of powder mixtures with the help of abrasive stripping voltammetry and coulometry

Summary Abrasive stripping voltammetry was applied to the quantitative analysis of the following powder mixtures: MnO₂-FeOOH, HgS-HgO, HgO-PbO. Therefore, g-amounts of the powder mixture were transferred onto a solid electrode and the electrochemical response of the solid sample is recorded. The calibration was made by measuring the percentage peak height of each component taking the sum of peak currents of both components as 100%. The relative standard deviation ranges from 3 to 15%. A calibration-free method based on microcoulometric measurements can be used in the case of powder mixtures of AgCl-AgI. The integration of staircase voltammograms directly yields the charges required to reduce AgCl and AgI and thus also gives the ratio of both components. The relative standard deviation was 10%. Microcoulometric measurements gave evidence that, in abrasive stripping voltammetry, the amount of electroactive substance ranges between 10^–12 and 10^–9 mole.On leave from University of Warsaw, Poland     

Synthesis of Tris(pentafluoroethyl)germanes

The synthesis of tris(pentafluoroethyl)germanium derivatives is described. The reaction of germanium tetrachloride with three equivalents of the pentafluoroethylation reagent LiC₂F₅ does not lead selectively to the formation of tris(pentafluoroethyl)chlorogermane, (C₂F₅)₃GeCl. Here the introduction of a diethylamino function as a protecting group was beneficial. Thus, treatment of Cl₃GeNEt₂ with LiC₂F₅ smoothly afforded (C₂F₅)₃GeNEt₂. The replacement of the amino substituent by halides was accomplished by reaction with HBr or HCl on a multigram scale. The combination of (C₂F₅)₃GeCl with Ag₂CO₃ gave rise to the formation of the digermoxane [(C₂F₅)₃Ge]₂O. An obtuse Ge‐O‐Ge angle of 150.2(1)° was determined by X‐ray diffraction. Attempted hydrolysis of the digermoxane leads to an equilibrium mixture of the precursor, (C₂F₅)₃GeOH, and water.     

Optimal control of molecular alignment in dissipative media

We explore the controllability of nonadiabatic alignment in dissipative media, and the information content of control experiments regarding the bath properties and the bath system interactions. Our approach is based on a solution of the quantum Liouville equation within the multilevel Bloch formalism, assuming Markovian dynamics. We find that the time and energy characteristics of the laser fields that produce desired alignment characteristics at a predetermined instant respond in distinct manners to decoherence and to population relaxation, and are sensitive to both time scales. In particular, the time-evolving spectral composition of the optimal pulse mirrors the time-evolving rotational composition of the wave packet, and points to different mechanisms of rotational excitation in isolated systems, in systems subject to a decoherering bath, and in ones subject to a population relaxing bath.     

The Bis(pentafluoroethyl)germylene Trimethylphosphane Adduct (C2F5)2Ge⋅PMe3: Characterization,Ligand Properties,and Reactivity

The synthesis of the germylene phosphane adduct (C₂F₅)₂Ge?PMe₃ is described. Starting from (C₂F₅)₃GeH in an excess of PMe₃, heating was applied, whereupon reductive elimination of C₂F₅H occurred. The molecular structure was ascertained by X‐ray diffraction and compared with information obtained by quantum chemical methods. The ligand properties were derived by studying the IR spectrum of the nickel(0) complex [Ni(CO)₃{Ge(C₂F₅)₂(PMe₃)}] in the CO region. (C₂F₅)₂Ge?PMe₃ turned out to be a π‐accepting ligand comparable to PMe₃, in terms of Tolman's electronic parameter. Furthermore a [2+4] cycloaddition reaction with 2,3‐dimethyl‐1,3‐butadiene, and σ‐bond insertion reactions were recorded. Activation of the C?Cl bond in dichloromethane gives rise to the formation of the phosphonium ylide complex [(C₂F₅)₂Cl₂Ge‐CH₂PMe₃], which was fully characterized by X‐ray diffraction.