Zur hochspannungselektrophoretischen Trennung anorganischer Ionen unter besonderer Berücksichtigung der Platinmetalle

Zusammenfassung Die hochspannungselektrophoretische Wanderung der Halogenokomplexe der Platinmetalle und weiterer anorganischer Ionen wird bei Anwendung von Polycarbonsäuren (Oxalsäure, Bernsteinsäure, Apfelsäure, Weinsäure und Zitronensäure) als Elektrolyt untersucht und der Einfluß des p_H-Werts und der Konzentration der Substanzen auf die Wanderung geprüft. Es wird festgestellt, daß die auf die abgestufte Komplexbildungstendenz der Polycarbonsäuren (Zitronensäure > Weinsäure Apfelsäure > Bernsteinsäure) rückführbaren Unterschiede der Wanderungsgeschwindigkeiten für die Trennung anorganischer Gemische gut einzusetzen sind. Für die Chlorokomplexe der Platinmetalle wird eine Abstufung der Beweglichkeiten in der Reihe Ir Pt Os > Rh > > Pd > Ru (> Rh) gefunden.

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The high voltage electrophoretic separation of inorganic ions with special consideration of the platinum metals

Summary The high voltage eleetrophoretic migration of the halogen complexes of the platinum metals and other inorganic ions was studied with the employment of the polycarboxylic acids (oxalic, succinic, malic, tartaric, citric) as electrolyte, and the influence of the p_H-value and the concentration of the substances on the migration investigated. It was found that the differences in the migration velocities, which may be traced back to the graded complex-forming tendency of the polycarboxylic acids (citric > tartaric malic > > succininic) can be used to good advantage in the separation of inorganic mixtures. With respect to the chlorocomplexes of the platinum metals, a decrease in the mobilities was discovered in the series Ir > Pt > Os > > Rh > Pd > Ru (>Rd).

     

High-speed gradient parallel liquid chromatography/tandem mass spectrometry with fully automated sample preparation for bioanalysis: 30 seconds per sample from plasma

In this work, a high-throughput and high-performance bioanalytical system is described that is capable of extracting and analyzing 1152 plasma samples within 10 hours. A Zymark track robot system interfaced with a Tecan Genesis liquid handler was used for simultaneous solid-phase extraction of four 96-well plates in a fully automated fashion. The extracted plasma samples were injected onto four parallel monolithic columns for separation via a four-injector autosampler. The use of monolithic columns allowed for fast and well-resolved separations at a considerably higher flow rate without generating significant column backpressure. This resulted in a total chromatographic run cycle time of 2 min on each 4.6 x 100 mm column using gradient elution. The effluent from the four columns was directed to a triple quadrupole mass spectrometer equipped with an indexed four-probe electrospray ionization source (Micromass MUX interface). Hence, sample extraction, separation, and detection were all performed in a four-channel parallel format that resulted in an overall throughput of about 30 s per sample from plasma. The performance of this system was evaluated by extracting and by analyzing twelve 96-well plates (1152) of human plasma samples spiked with oxazepam at different concentrations. The relative standard deviation (RSD) of analyte sensitivity (slope of calibration curve) across the four channels and across the 12 plates was 5.2 and 6.8%, respectively. An average extraction recovery of 77.6% with a RSD of 7.7% and an average matrix effect of 0.95 with a RSD of 5.2% were achieved using these generic extraction and separation conditions. The good separation efficiency provided by this system allowed for rapid method development of an assay quantifying the drug candidate and its close structural analog metabolite. The method was cross-validated with a conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay.     

pH‐Dependent Coordination of AgI Ions by Histidine: Experiment,Theory, and a Model for SilE

Artificial implants and biomaterials lack the natural defense system of our body and, thus, have to be protected from bacterial adhesion and biofilm formation. In addition to the increasing number of implanted objects, the resistance of bacteria is also an important problem. Silver ions are well‐known for their antimicrobial properties, yet not a lot is known about their mode of action. Silver is expected to interact on many levels, thus the development of silver resistance is very difficult. Nevertheless, some bacteria are able to resist silver, even at higher concentrations. One such defense mechanism of bacteria against heavy‐metal intoxication includes an efflux system. SilE, a periplasmic silver‐binding protein that is involved in this defense mechanism, has been shown to possess numerous histidine functions, which strongly bind to silver atoms, as demonstrated by ourselves previously. Herein, we address the question of how histidine binds to silver ions as a function of pH value. This property is important because the local proton concentration in cells varies. Thus, we solved the crystal structures of histidine–silver complexes at different pH values and also investigated the influence of the amino‐acid configuration. These results were completed by DFT calculations on the binding strength and packing effects and led to the development of a model for the mode of action of SilE.     

Alkyl 2-(2-benzoyl-2-ethoxycarbonyl-1-ethenyl)amino-3-dimethylaminopropenoates in the synthesis of heterocyclic systems

Alkyl 2-(2-benzoyl-2-ethoxycarbonyl-1-ethenyl)amino-3-dimethylaminopropenoates 4a,b were prepared. They react with C-nucleophiles such a 2-pyridinylacetonitrile 5 and methyl-2-quinolinylacetate 8, cyclohexane-1,3-dione 10 and its derivatives 12 and 14, resorcinol derivative 16 , 2-naphtol 18, 2-pyranone derivatives 20 and 22, and 4-hydroxypyridin-2(1H)-one 24, to form substituted amino derivatives of quinolizine 6, benzo[c]quinolizine 9, tetrahydrobenzopyran-2-one 11, 13, 15 , naphto[2,1-b]pyran-3-one 19 , pyranopyranones 21, 23, and pyrano[3,2-c]pyridine 25.