Die Darstellung der Oligosilane Si8 X 18 (X-Cl,OCH3) durch Photolyse von Silylquecksilberverbindungen

The formation of SiSi-bonds by a photochemical reaction of silylmercury compounds is described. The silylmercury compounds [(X ₃Si)₃Si]₂Hg (X=Cl, OCH₃) were synthesized via theVyazankin Hydrid method with (X ₃Si)₃SiH and Bis(t-butyl)mercury. By UV-irradiation of these products in hexane as a solvent, the oligosilanes [(X ₃Si)₃Si]₂ are formed in good yields. All these compounds are charactericed by spectroscopical methods.

     

Isolation and some characterisation of antifreeze protein from the European eelpout Zoarces viviparus

The European eelpout Zoarces viviparus is a common inhabitant in the coastal areas of the eastern Atlantic Ocean and the Baltic region. At least 3 different antifreeze proteins were purified from Z. viviparus serum but more isoforms are most likely present. Two antifreeze proteins with molecular weights of approx. 6.5-7 kDa were characterised and found to share high similarity to the type III antifreeze proteins found in other members of the family Zoarcidae. The antifreeze activity of Z. viviparus antifreeze proteins is concentration dependent and showed a saturation effect when the protein concentration reached 30 mg.ml-1 (crude serum) and 8 mg.ml-1 (partly purified serum) respectively. Further the antifreeze activity was found to be dependent of the buffer osmolality resulting in increasing thermal hysteresis when buffer osmolality was raised from 0 to 1M.     

Multivariate metabolic profiling using 1H nuclear magnetic resonance spectroscopy of freeze-tolerant and freeze-intolerant earthworms exposed to frost

Individuals of the freeze-tolerant earthworm, Dendrobaena octaedra, and four freeze-intolerant earthworm species (Dendrodrilus rubidus, Aporrectodea icterica, A. caliginosa, and A. longa) were frozen at -2 degree C. Control earthworms were exposed to +2 degree C. 1H nuclear magnetic resonance spectroscopy-based metabolic profiling in combination with multivariate pattern recognition methods (metabonomics) was used to produce a cross-species comparison. Several biochemical changes were detected as a result of freezing in all worm species, including an increase in relative free alanine concentrations, and an apparent conversion of adenosine to inosine. It was also possible to determine a number of biochemical changes that were unique to the freeze-tolerant species, D. octaedra. The most obvious difference was that, although all species showed an increase in glucose concentrations, the increase was largest in D. octaedra, and was coupled with a concomitant decrease in glycogen. This confirms that--like previously studied freeze-tolerant earthworm species--tolerance is effected by rapid glucose production from glycogen reserves. An additional difference noted was that succinate increased in all species on freezing, but the increase was least in D. octaedra. Furthermore there was no lactate accumulation in D. octaedra, whereas three of the other four species accumulated lactate. This indicates that anoxic metabolism was lowest in the freeze-tolerant species.     

Arsenic speciation in freshwater organisms from the river Danube in Hungary

Total arsenic and arsenic species were determined in a range of freshwater samples (sediment, water, algae, plants, sponge, mussels, frog and fish species), collected in June 2004 from the river Danube in Hungary. Total arsenic concentrations were measured by ICPMS and arsenic species were measured in aqueous extracts of the samples by ion-exchange HPLC-ICPMS. In order to separately determine the efficiency of the extraction method and the column recovery, total arsenic concentrations in the extracts were obtained in three ways: (i) ICPMS determination after acid digestion; (ii) flow injection analysis performed directly on the extract; (iii) the sum of arsenic species eluting from the HPLC column. Extraction efficiencies were low (range 10-64%, mean 36%), but column recovery was acceptable (generally >80%) except for the fish samples, where substantial, currently unexplained, losses were observed. The dominating arsenic species in the extracts of freshwater algae were arsenosugars, whereas arsenate [As(V)] was present only as a minor constituent. On the other hand, plant extracts contained only inorganic arsenic, except for two samples which contained trace amounts of dimethylarsinate (DMA) and the tetramethylarsonium cation (TETRA). The oxo-arsenosugar-phosphate (ca. 35% of extractable arsenic) and the oxo-arsenosugar-glycerol (ca. 20%) as well as their thio-analogues (1-10%) were found in the mussel extracts, while arsenobetaine (AB) was present as a minor species only. In general, fish extracts contained only traces of arsenobetaine, and the oxo-arsenosugar-phosphate was the major arsenic compound. In addition, samples of white bream contained thio-arsenosugar-phosphate; this is the first report of a thio-arsenical in a fish sample. The frog presented an interesting arsenic speciation pattern because in addition to the major species, arsenite [As(III)] (30%) and the tetramethylarsonium cation (35%), all three intermediate methylation products, methylarsonate (MA), dimethylarsinate and trimethylarsine oxide (TMAO), and arsenate were also present. Collectively, the data indicate that arsenobetaine, the major arsenical in marine animals, is virtually absent in the freshwater animals investigated, and this represents the major difference in arsenic speciation between the two groups of organisms.     

Maternal-fetal relations in antifreeze production in the eelpout Zoarces viviparus

The viviparous teleost Zoarces viviparus inhabits the coastal areas of the eastern North Atlantic and Baltic region. Antifreeze activity was measured in serum from pregnant females and embryos during their embryological development inside the ovary and found to be up to 0.95 degree C and 0.85 degree C respectively. Lower levels of antifreeze activity (up to 0.34 C) were discovered in the ovarian fluid. The result is higher hysteresis freezing points and thus less protection to freezing of the ovarian fluid compared to the serum in embryos and the maternal organism. The pertinence of this to the cold tolerance of Z. viviparus is presently unknown. SDS-PAGE of ovarian fluid shows only few protein bands and a difference in proportional density of proteins compared to maternal and embryo serum. This could indicate that another mechanism than rupture of blood vessels in the ovarian wall is of importance for the occurrence of small proteins in the ovarian fluid.     

Zum aminkatalysierten Abbau von Oligochlorsilan mit HCl

Tetrakis(trichlorosilyl)silan (neo-Si₅Cl₁₂) is cleaved in an amine catalysed reaction by HCl in benzene solution to tris(trichlorosilyl)silan HSi(SiCl₃)₃ (1). The amine catalysed cleavage of1 with different amines and solvents is investigated. A new method for preparation of pentachlorodisilane HSi₂Cl₅ is described and a reaction mechanism for the cleavage is postulated.

     

Matrix removal in state of the art sample preparation methods for serum by charged aerosol detection and metabolomics-based LC-MS

Investigations into sample preparation procedures usually focus on analyte recovery with no information provided about the fate of other components of the sample (matrix). For many analyses, however, and particularly those using liquid chromatography-mass spectrometry (LC-MS), quantitative measurements are greatly influenced by sample matrix. Using the example of the drug amitriptyline and three of its metabolites in serum, we performed a comprehensive investigation of nine commonly used sample clean-up procedures in terms of their suitability for preparing serum samples. We were monitoring the undesired matrix compounds using a combination of charged aerosol detection (CAD), LC-CAD, and a metabolomics-based LC-MS/MS approach. In this way, we compared analyte recovery of protein precipitation-, liquid-liquid-, solid-phase- and hybrid solid-phase extraction methods. Although all methods provided acceptable recoveries, the highest recovery was obtained by protein precipitation with acetonitrile/formic acid (amitriptyline 113%, nortriptyline 92%, 10-hydroxyamitriptyline 89%, and amitriptyline N-oxide 96%). The quantification of matrix removal by LC-CAD showed that the solid phase extraction method (SPE) provided the lowest remaining matrix load (48–123 μg mL⁻¹), which is a 10–40 fold better matrix clean-up than the precipitation- or hybrid solid phase extraction methods. The metabolomics profiles of eleven compound classes, comprising 70 matrix compounds showed the trends of compound class removal for each sample preparation strategy. The collective data set of analyte recovery, matrix removal and matrix compound profile was used to assess the effectiveness of each sample preparation method. The best performance in matrix clean-up and practical handling of small sample volumes was showed by the SPE techniques, particularly HLB SPE. CAD proved to be an effective tool for revealing the considerable differences between the sample preparation methods. This detector can be used to follow matrix compound elution during chromatographic separations, and the facile monitoring of matrix signal can assist in avoiding unfavourable matrix effects on analyte quantification.     

Darstellung und Eigenschaften einiger Hochchlorierter Oligosilane

Preparation and Properties of Some Highly Chlorinated Oligosilanes Tetrakis(trichlorosilyl)silane (neo-Si₅Cl₁₂) is cleaved by HCl in SiCl₄ solution to tris(trichlorosilyl)silane, HSi(SiCl₃)₃, and SiCl₄. HSi(SiCl₃)₃ and bis(trichlorosilyl)silane, H₂Si(SiCl₃)₂, can also be prepared in good yield by reaction of the methoxy compounds HSi[Si(OCH₃)₃]₃ and H₂Si[Si(OCH₃)₃]₂ with BCl₃. The mass, ¹H-n.m.r., and vibrational spectra of HSi(SiCl₃)₃ and H₂Si(SiCl₃) as well as some ¹H-n.m.r. data of HClSi(SiCl₃)₂, HCl₂SiSiCl₃ and H₂ClSiSiCl₃ are reported and discussed. An improved synthesis for neo-Si₅Cl₁₂ is given.