Solvent Effects on kp in Organic Media?: Statement to the Response

A recent response on a publication from our team investigating solvent effects on propagation rate coefficients is commented. Among other issues, we point to the fact that the response interprets only a subset of the data provided in our original contribution.

     

Enantioselective capillary electrophoresis for pharmacokinetic analysis of methadone and 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in equines anesthetized with ketamine and isoflurane

An enantioselective assay for the determination of methadone and its main metabolite 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in equine plasma based on capillary electrophoresis with highly sulfated γ‐cyclodextrin as chiral selector and electrokinetic analyte injection is described. The assay is based on liquid/liquid extraction of the analytes at alkaline pH from 0.1 mL plasma followed by electrokinetic sample injection of the analytes from the extract across a buffer plug without chiral selector. Separation occurs cationically at normal polarity in a pH 3 phosphate buffer containing 0.16% (w/v) of highly sulfated γ‐cyclodextrin. The developed assay is precise (intra‐ and interday RSD < 4% and < 7%, respectively), is capable to determine enantiomer levels of methadone and 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine in plasma down to 2.5 ng/mL, and was successfully applied to monitor enantiomer drug and metabolite levels in plasma of a pony that was anesthetized with racemic ketamine and isoflurane and received a bolus of racemic methadone and a bolus followed by constant rate infusion of racemic methadone. The data suggest that the assay is well suited for pharmacokinetic purposes.     

Semi-Synthesis and Analysis of Chemically Modified Zif268 Zinc-Finger Domains

Total synthesis of proteins can be challenging despite assembling techniques, such as native chemical ligation (NCL) and expressed protein ligation (EPL). Especially, the combination of recombinant protein expression and chemically addressable solid-phase peptide synthesis (SPPS) is well suited for the redesign of native protein structures. Incorporation of analytical probes and artificial amino acids into full-length natural protein domains, such as the sequence-specific DNA binding zinc-finger motifs, are of interest combining selective DNA recognition and artificial function. The semi-synthesis of the natural 90 amino acid long sequence of the zinc-finger domain of Zif268 is described including various chemically modified constructs. Our approach offers the possibility to exchange any amino acid within the third zinc finger. The realized modifications of the natural sequence include point mutations, attachment of a fluorophore, and the exchange of amino acids at different positions in the zinc finger by artificial amino acids to create additional metal binding sites. The individual constructs were analyzed by circular dichroism (CD) spectroscopy with respect to the integrity of the zinc-finger fold and DNA binding.     

A combined laser-induced breakdown and Raman spectroscopy Echelle system for elemental and molecular microanalysis

Raman and laser-induced breakdown spectroscopy is integrated into a single system for molecular and elemental microanalyses. Both analyses are performed on the same ~ 0.002 mm² sample spot allowing the assessment of sample heterogeneity on a micrometric scale through mapping and scanning. The core of the spectrometer system is a novel high resolution dual arm Echelle spectrograph utilized for both techniques. In contrast to scanning Raman spectroscopy systems, the Echelle–Raman spectrograph provides a high resolution spectrum in a broad spectral range of 200–6000 cm^? 1 without moving the dispersive element. The system displays comparable or better sensitivity and spectral resolution in comparison to a state-of-the-art scanning Raman microscope and allows short analysis times for both Raman and laser induced breakdown spectroscopy. The laser-induced breakdown spectroscopy performance of the system is characterized by ppm detection limits, high spectral resolving power (15,000), and broad spectral range (290–945 nm). The capability of the system is demonstrated with the mapping of heterogeneous mineral samples and layer by layer analysis of pigments revealing the advantages of combining the techniques in a single unified set-up.     

Hydrophobic dendrimers as templates for au nanoparticles

We report the synthesis, characterization, and extraction of Au dendrimer-encapsulated nanoparticles (DENs) prepared in organic solvents. DENs composed of 31 and 55 Au atoms were prepared using organic solvents and poly(amidoamine) (PAMAM) dendrimer templates modified on their periphery with dodecyl groups. The spectral and microscopic properties of the resulting materials were identical to those prepared using water-soluble PAMAM dendrimers. It was possible to extract the organic-soluble DENs into water using the water-soluble thiols tiopronin and glutathione. The properties of the resulting monolayer-protected clusters were nearly identical to those of the precursor DENs. A mechanistic model for the extraction process is discussed. The synthetic methodology reported here provides a convenient method for preparing DENs of non noble metals such as Ni and Fe.     

Quantitative Analyse von Zeolithen mit Hilfe der Röntgenphotoelektronenspektroskopie

Analytical and Bioanalytical Chemistry - Die Oberflächenzusammensetzung von Zeolithen des Typs A, die mit verschiedenen Mengen Eisen ausgetauscht worden waren, wurde mit der...     

Normales Erstarren, Zonenschmelzen und Kolonnenkristallisieren

Ohne ZusammenfassungFür sehr gute Zusammenarbeit danke ich. meinen Mitarbeitern, Herrn Dr. H. Vetter, Dipl.chem. F. Schlegelmilch, Frl. Dipl.chem. U. Hopf und Frl. Dipl.chem. S. Rössler, sowie Herrn Dipl.chem. K. Maas.Unsere Arbeiten wurden wesentlich gefördert durch dankenswerte Unterstützung, finanzieller und sachlicher Art, vom Bundesministerium für Atomkernenergie und Wasserwirtschaft, der Max Büchner-Stiftung und der Deutschen Forschungsgemeinschaft.