Analysis of tellurium by spark source mass spectrometry

Summary Three tellurium standards were analyzed by both spark source mass spectrometry (SSMS) and graphite furnace atomic absorption spectrophotometry (GFAAS). From these results relative sensitivity coefficients (RSC) for spark source mass spectrometry were derived for 24 elements.With these RSC's SSMS results within a factor 1.5 from the GFAAS values could be obtained for the determination of various impurities in tellurium. A comparison is made between SSMS, GFAAS and glow discharge mass spectrometry (GDMS) for the analysis of 4–6 N tellurium samples.

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Analyse von Tellurium mit Hilfe der Funkenionisations-Massenspektrometrie

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Dedicated to Prof, Dr. G. Tölg on the occasion of his 60th birthday     

Efficiency control in large-scale genotyping using analysis of variance

The efficiency of the genotyping process is determined by many simultaneous factors. In actual genotyping, a production run is often preceded by small-scale experiments to find optimal conditions. We propose to use statistical analysis of production run data as well, to gain insight into factors important for the outcome of genotyping. As an example, we show that analysis of variance (ANOVA) applied to the first-pass results of a genetic study reveals important determinants of genotyping success. The largest factor limiting genotyping appeared to be interindividual variation among DNA samples, explaining 20% of the variance, and a smaller reaction volume, sizing failure, and differences among markers all explained ∼10%. Other potentially important factors, such as sample position within the plate and reusing electrophoresis matrix, appeared to be of minor influence. About 55% of the total variance could be explained by systematic factors. These results show that ANOVA can provide valuable feedback to improve genotyping efficiency. We propose to adjust genotype production runs using principles of experimental design in order to maximize genotyping efficiency at little additional cost.     

Peptidomic analysis of the larval Drosophila melanogaster central nervous system by two-dimensional capillary liquid chromatography quadrupole time-of-flight mass spectrometry

Peptides are the largest class of signalling molecules found in animals. Nevertheless, in most proteomic studies peptides are overlooked since they literally fall through the mazes of the net. In analogy with proteomics technology, where all proteins expressed in a cell or tissue are analyzed, the peptidomic approach aims at the simultaneous visualization and identification of the whole peptidome of a cell or tissue, i.e. all expressed peptides with their post-translational modifications. In this paper we describe the analysis of the larval fruit fly central nervous system using two-dimensional capillary liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/Q-TOF-MS/MS. Using the central nervous systems of only 50 larval Drosophila as starting material, we identified 38 peptides in a single analysis, 20 of which were not detected in a previous study that reported on the one-dimensional capillary LC/MS/MS analysis of the same tissue. Among the 38 sequenced peptides, some originate from precursors, such as the tachykinin and the IFamide precursor that were entirely missed in the first study. This clearly demonstrates that the two-dimensional capillary LC approach enhances the coverage of the peptidomic analysis.     

Absorption cross-sections of NO2 in the UV and visible region (200 – 700 nm) at 298 K

The absorption cross-sections of NO₂ have been measured in the wavelength range 200 – 700 nm at 298 K with a spectral resolution of 0.04 nm. The data were acquired digitally, allowing post-processing such as integration in different wavelength intervals. The cross-sections are averaged over 1 nm intervals and over the atmospheric wavelength intervals used in solar photolysis calculations.     

Synthetic Receptors for the High‐Affinity Recognition of O‐GlcNAc Derivatives

The combination of a pyrenyl tetraamine with an isophthaloyl spacer has led to two new water‐soluble carbohydrate receptors (“synthetic lectins”). Both systems show outstanding affinities for derivatives of N‐acetylglucosamine (GlcNAc) in aqueous solution. One receptor binds the methyl glycoside GlcNAc‐β‐OMe with K_a≈20 000 m ^?1, whereas the other one binds an O‐GlcNAcylated peptide with K_a≈70 000 m ^?1. These values substantially exceed those usually measured for GlcNAc‐binding lectins. Slow exchange on the NMR timescale enabled structural determinations for several complexes. As expected, the carbohydrate units are sandwiched between the pyrenes, with the alkoxy and NHAc groups emerging at the sides. The high affinity of the GlcNAcyl–peptide complex can be explained by extra‐cavity interactions, raising the possibility of a family of complementary receptors for O‐GlcNAc in different contexts.     

Ring-closing metathesis and ring-closing metathesis-isomerisation approach to 1-phosphonylated 2-benzazocines

An RCM strategy has been developed for the synthesis of phosphonylated benzazocines and their corresponding isomerised analogues. The aminophosphonate precursors were obtained by a one-pot three-component condensation in moderate yield.     

Superagonistic fluorinated vitamin D3 analogs stabilize helix 12 of the vitamin D receptor

Side chain fluorination is often used to make analogs of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] resistant to degradation by 24-hydroxylase. The fluorinated nonsteroidal analogs CD578, WU515, and WY1113 have an increased prodifferentiating action on SW480-ADH colon cancer cells, which correlated with stronger induction of vitamin D receptor (VDR)-coactivator interactions and stronger repression of beta-catenin/TCF activity. Cocrystallization of analog CD578 with the zebrafish (z)VDR and an SRC-1 coactivator peptide showed that the fluorine atoms of CD578 make additional contacts with Val444 and Phe448 of activation helix 12 (H12) of the zVDR and with Leu440 of the H11-H12 loop. Consequently, the SRC-1 peptide makes more contacts with the VDR-CD578 complex than with the VDR-1,25(OH)2D3 complex. These data show that fluorination not only affects degradation of an analog but can also have direct effects on H12 stabilization.     

The deterioration of closed silica tubes in hydride-generation atomic absorption spectrometry

Under the conditions normally encountered in hydride evolution for atomic absorption spectrometry, devitrification of quartz to β-cristobalite occurs. For selenium, this devitrification is detrimental to the analytical characteristics of the method. Analytical performance and the life-span of the atomizer can be dramatically improved by the use of sulfuric acid instead of hydrochloric acid in the generation medium. An attempt is made to explain the deterioration and its possible influence on the atomization of hydrogen selenide.