A rapid and simple cleanup procedure for metathesis reactions

[structure: see text]. A new method for easy removal of ruthenium from metathesis reactions by using a polar isocyanide is reported. This protocol removed most ruthenium byproducts from a variety of synthetically useful metatheses. Moreover, the isocyanide-promoted carbene insertion results in rapid destruction of carbene reactivity, demonstrated in the commonly used first- and second-generation Grubbs' carbenes.     

Mercury speciation in hair by headspace injection-gas chromatography-atomic fluorescence spectrometry (methylmercury) and combustion-atomic absorption spectrometry (total Hg)

The speciation of Hg in human hair was carried out with combustion-atomic absorption spectrometry for total Hg (THg) and headspace-gas chromatography-atomic fluorescence spectrometry (HS-GC-AFS) for methylmercury (MMHg).The determination of total Hg in hair was carried out with the AMA analyzer (Advanced Mercury Analyser 254). Accuracy and reproducibility were assessed on a Certified Reference hair sample (IAEA-086 CRM), yielding, respectively, a recovery of 97.5% and a RSD of 3.2%. Analyses of 10 blank measurements resulted in a detection limit of 1.5 ng g⁻¹ of THg for a 20 mg sample of human hair.MMHg concentrations in hair were assessed with HS-GC-AFS in a single analysis step. Either acid or alkaline extraction can be applied because they yielded very similar results on a IAEA-086 CRM: we observed a recovery of 103% and a RSD of 7% with acid extraction and a recovery of 110% and a RSD of 9% with alkaline extraction. Optimization of the headspace vial, injection and GC parameters is described. The detection limit of the MMHg determination in human hair, which amounts to 0.04 ng g⁻¹ for a 20 mg sample, is far below the concentrations observed in natural samples.The number of samples that can be analyzed per hour, respectively, amounts to 8 for THg and 4 for MMHg. Finally, Hg speciation in natural human hair samples was carried out by combining both AMA and HS-GC-AFS analysis methods. THg levels were at the μg g⁻¹, level, with an average MMHg fraction of about 70%.     

Playing tag with quantitative proteomics

There is steady need for new proteomic strategies on quantitative measurements that provide essential components for detailing dynamic changes in many cellular functions and processes. Stable isotope labeling is a rapidly evolving field, which can be used either after protein extraction with chemical labeling, or in cell culture with metabolic incorporation. In this review, we explore the most frequently utilized quantitation techniques with particular attention paid to chemical labeling using different isotopic tags, including a recent labeling strategy—soluble polymer-based isotopic labeling (SoPIL)—that achieves efficient labeling in homogeneous conditions. Special care should be devoted to the selection of appropriate quantitation approaches according to the needs of the sample and overall experimental design. We evaluate recent advances in quantitative proteomics using stable isotope labeling and their applications to current insightful biological inquiries. Figure Chemical modules of isotopic tags for quantitative proteomics.     

α-Selective Organocatalytic Synthesis of 2-Deoxygalactosides

Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety. The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism.     

Construction and performance of an a.c. modulated magnet for Zeeman atomic absorption spectroscopy

A Zeeman atomic absorption spectroscopy system has been constructed utilizing a 50 Hz sine wave modulated magnetic field that can be directed either parallel or perpendicular to the optical axis. The amplitude of the magnetic field strength is adjustable up to 10 kG at a maximum power consumption of 0.7 kW.The readout system allows normal atomic absorption as well as d.c. and a.c. Zeeman atomic absorption measurements. Plots of experimental sensitivity vs magnetic field strength and analytical curves are in agreement with theoretical predictions.Experiments in the presence of filter simulated and real background absorbance show that the described Zeeman instrument is capable of correcting background absorption up to two absorbance units.     

The160Tb →160Dy decay

Gamma-ray spectra in the decay of¹⁶⁰Tb were measured with the aid of two coaxial Ge(Li) spectrometers. Absolute intensities and multipolarities were obtained. Three new transitions of 486·5 keV, 1069 keV, and 1102·5 keV were found and introduced into the decay scheme. The level scheme is discussed from the point of view of the generalized model of the nucleus. Experimental data show the 1264·4 keV level to be a two-quasi-particle state of the p p (411–523) type. The beta-transition from the ground state of¹⁶⁰Tb (p 411+n 521) to this two-quasi-particle state with logft=8·00 ± 0·05 is interpreted as -forbidden.The authors are indebted to Prof. K. E. Alexandrov, K. A. Gromov, and E. P. Grigoriev for useful remarks and interest concerning the work.     

The structure of the excited states in84Rb

Conclusion On the basis of the simple shell-model the anomalously high admixture of the E4-radiation to the M3-transition deexciting the isomeric state^84mRb has been explained. The exact evaluation of the amount of this admixture would require, however, detailed theoretical calculations considerating the configuration mixing in the wave functions of the 3⁺ and 6⁺ states in⁸⁴Rb.     

Influence of the temporal response of the detection system upon atomic absorption analytical curves for steady state and transient absorption cells and

The general expression for the atomic absorption signal is modified to allow for a possible time-dependence of the source emission line profile and the     

Data treatment in multi-wavelength detection in HPLC of biochemical compounds

Summary The paper discusses the various methods for the processing of data obtained for the separation of proteins with HPLC equipped with a multi-wavelength detector. Specific difficulties are encountered because of the complexity of protein mixtures and the high similarity of protein spectra. Depending on the type of the requested information, proper data treatment methods should be selected. These are: ratio recording, multi-component analysis and curve resolution.

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Datenverarbeitung für die Multi-Wellenlängen-Detektion bei der HPLC von biochemischen Verbindungen

Zusammenfassung Die verschiedenen Methoden werden diskutiert zur Verarbeitung der bei der HPLC-Trennung von Proteinen mit Hilfe eines Multi-Wellenlängen-Detektors erhaltenen Daten. Spezifische Schwierigkeiten treten dabei auf wegen der Komplexität von Proteingemischen und der großen Ähnlichkeit der Spektren. Je nach Art der gewünschten Information sollten die geeigneten Datenverarbeitungsverfahren ausgewählt werden: Verhältnis-Registrierung, Mehrkomponenten-Analyse und Kurvenauflösung.