Addition reactions of the trichlorocyclopropenylium ion with alkenes. A novel access to cyclopropene and cyclopropenone derivatives

Trichlorocyclopropenylium tetrachloroaluminate 1+-AlCl−4 reacts with alkenes in nitromethane at −35°C to give the 1:1 addition products 2+-AlCl−4, which can be converted into the 2-chlorocyclopropenones 5 or the ä,β-acetylenic carboxylates 6

Isolation and Characterization of a Cellular Protein-Lipid Complex from Ascites Fluid Caused by Various Neoplasms

High concentrations of lipids in ascites fluid caused by peritoneal carcinomatosis have been described recently. Since their nature has not yet been clarified, we isolated ascitic lipids from 25 patients with various neoplasms for further characterization. After chromatography on Sephadex G-100 gels, the ascitic lipids were fractionated on a Biogel A-5m column in three peaks. The second and third peaks were identified as low and high density lipoproteins, which were most likely of plasmatic origin, and represented the major amounts of ascitic lipids. The first peak was eluted in the void volume, indicating a molecular weight over 5 million. It consisted, on the average, of 65.3% protein, 16.2% triglycerides, 7.4% phospholipids, and 7.0% cholesterol. In a CsCl gradient, this protein-lipid complex floated in the density range from 1.128 to 1.181 g/ml. Sodium dodecyl sulfate: polyacrylamide gel electrophoresis separated up to 11 protein subunits (Mr 29,000 to 97,000), and electron microscopy revealed globular particles of 36 to 64 nm in diameter. The macromolecular complex showed no immunological reaction against anti-{alpha}- and anti-ß-lipoproteins, but a single precipitation line against anti-liver-specific lipoprotein was seen. The biochemical characteristics of this protein-lipid complex proved to have a close relationship to liver-specific lipoprotein. It is most likely derived from cell membranes of the peritoneum detached by carcinomatosis

Synthesis, Structure, and Dynamics of Tris(η5-cyclopentadienyl)lanthanides and Bis(η5-cyclopentadienyl)[bis(trimethylsilyl)amido]cerium(III)

The crystal structures of tris(η5-cyclopentadienyl)lanthanides (Ln = Ce, Dy, Ho) have been determined using different X-ray diffraction methods. Cp3Ce and Cp3Ho (Cp = cyclopentadienyl) crystal data needed special solution and refinement methods, due to the occurrence of intrinsic twinning in these species. Our results do not agree with the previously published cell constants of Cp3Ho. The space group and unit cell parameters of Cp3Dy have been derived from powder diffraction experiments. High-resolution 13C solid-state NMR data of Cp3La are presented, giving evidence of the dynamics and bonding situation of the Cp ligands. Cp3Ce turned out to be a reactive reagent for the synthesis of bis(η5-cyclopentadienyl)[bis(trimethylsilyl)amido]cerium(III)

Urinary cholesterol: its association with a macromolecular protein- lipid complex

The cholesterol-containing complexes in the urine of normal subjects and patients with diseases accompanied by hyperexcretion of urinary cholesterol were characterized. In normal subjects, the major portion of the recovered urinary cholesterol was eluted in the void volume fractions after gel chromatography on Bio-Gel A-5m; this suggested an association with a macromolecular complex above 5 X 10(6) daltons. A comparable elution pattern was seen in most of the urines of the patients with benign or malignant diseases of the kidneys or the urogenital tract. However, in single patients with hyperexcretion of urinary cholesterol, considerable amounts of cholesterol were detected in the included volume of the column. This was caused by additional excretion of high density lipoproteins or both high and low density lipoproteins in the urine which could be identified in these fractions by agarose electrophoresis and immunodiffusion. These results indicate that the macromolecular complex represents the majority of the recovered urinary cholesterol in normal subjects and in disease states with known hyperexcretion. Macroscopically, the isolated cholesterol- containing complex in the void volume fractions was turbid, and electron microscopy showed lipoprotein-like particles with diameters ranging from 300 to 700 A. The chemical analysis revealed median values of protein (46.0%), triglycerides (16.3%), cholesterol (8.2%), and phospholipids (29.5%) in normal subjects and comparable results in the patients with benign or malignant diseases of the kidney and the urogenital tract. Ethanolamine glycerophospholipids, phosphatidylcholine, sphingomyelin, and phosphatidylserine were the main phospholipid components. After ultracentrifugation in a CsCl gradient, the cholesterol-containing complex was found between densities 1.1 and 1.3 g/ml. By SDS polyacrylamide electrophoresis, up to 17 protein subunits in the molecular weight range of 14,000 to 87,500 were separated. Immunodiffusion studies showed in about 40% precipitin lines against anti-human albumin, but no reactions against anti-human apoHDL and anti-human apoLDL. However, immunodiffusion of the macromolecular complex against anti-liver-specific and anti-kidney- specific lipoproteins revealed single precipitin lines. In conclusion, the isolated cholesterol-containing urinary complex showed many characteristics of membrane-associated protein-lipid particles of the human kidney and even the liver. These proteolipids are the major source of urinary cholesterol in normal and disease states

A comparative study of Tam3 and Ac transposition in transgenic tobacco and petunia plants

Transposition of the Anthirrinum majus Tam3 element and the Zea mays Ac element has been monitored in petunia and tobacco plants. Plant vectors were constructed with the transposable elements cloned into the leader sequence of a marker gene. Agrobacterium tumefaciens-mediated leaf disc transformation was used to introduce the transposable element constructs into plant cells. In transgenic plants, excision of the transposable element restores gene expression and results in a clearly distinguishable phenotype. Based on restored expression of the hygromycin phosphotransferase II (HPTII) gene, we established that Tam3 excises in 30% of the transformed petunia plants and in 60% of the transformed tobacco plants. Ac excises from the HPTII gene with comparable frequencies (30%) in both plant species. When the β-glucuronidase (GUS) gene was used to detect transposition of Tam3, a significantly lower excision frequency (13%) was found in both plant species. It could be shown that deletion of parts of the transposable elements Tam3 and Ac, removing either one of the terminal inverted repeats (TIR) or part of the presumptive transposase coding region, abolished the excision from the marker genes. This demonstrates that excision of the transposable element Tam3 in heterologous plant species, as documented for the autonomous element Ac, also depends on both properties. Southern blot hybridization shows the expected excision pattern and the reintegration of Tam3 and Ac elements into the genome of tobacco plants.

A latitudinal cline in the efficacy of endogenous signals: evidence derived from retinal cone contraction in fish.

Like many physiological systems synchronised to the light:dark cycle, retinomotor movements in 'lower' vertebrates are controlled by both the ambient illumination and input from endogenous circadian oscillators. In the present study, we examine the relative influence of these two signals in various species of teleost fish with different latitudes of origin. We find equatorial species show very strong endogenous control. The cones of the glowlight tetra, for example, continue to go through undiminished cycles of contraction and relaxation that mirror the previous light:dark cycle for at least two weeks in continual darkness. To quantify the relative effectiveness of the ambient light compared with endogenous signals in causing cone contraction, the degree to which seven teleost species responded to light during the dark phase of their light:dark cycle was examined. In this situation the retina receives conflicting instructions; while the light is acting directly to cause light adaptation, any endogenous signal tends to keep the retinal elements dark adapted. The further from the equator a species originated, the more its cones contracted in response to such illumination, suggesting animals from higher latitudes make little use of endogenous oscillators and rely more on ambient illumination to control behaviours. Equatorial species, however, rely on internal pacemakers to a much greater degree and are relatively insensitive to exogenous light signals. Because these data are consistent with published observations in systems as diverse as melatonin synthesis in Arctic reindeer and the behaviour of regional populations of Drosophila, latitudinal clines in the efficacy of circadian oscillators may be a common feature among animals

Scatter factor : molecular characteristics and effect on the invasiveness of epithelial cells

The generation of invasiveness in transformed cells represents an essential step of tumor progression. We have previously shown that MDCK epithelial cells, which are deprived of intracellular adhesion by the addition of anti-Arc-1/uvomorulin antibodies, become invasive for collagen gels and embryonal heart tissue (Behrens, J., M. M. Mareel, F. M. Van Roy, and W. Birchmeier. 1989. J. Cell Biol. 108: 2435-2447.). Here we examined whether invasiveness is also induced by scatter factor, which is known to dissociate epithelial cells (Stoker, M., E. Gherardi, M. Perryman, and J. Gray. 1987. Nature (Lond.). 327:239-242.). Scatter factor was purified to homogeneity from conditioned medium of human fibroblasts by heparin-Sepharose chromatography, followed by cation exchange chromatography, gel filtration, or preparative SDS gel electrophoresis. We found that scatter factor represents a 92,000 mol wt glycoprotein which, apparently, is converted by limited proteolysis into disulfide-linked 62,000 and 34/32,000 mol wt subunits. Reversed phase HPLC and sequence analysis of tryptic peptides confirmed the suggested molecular structure, and revealed further that scatter factor exhibits sequence similarities to hepatocyte growth factor and to plasminogen. Purified scatter factor in fact induces the invasiveness into collagen matrices of MDCK epithelial cells, and induces or promotes the invasiveness of a number of human carcinoma cell lines. Apparently, the effect on the human cells depends on their respective degree of differentiation, i.e., cell lines with a less pronounced epithelial phenotype were more susceptible to the factor. Scatter factor does not seem to influence synthesis, steady-state level, and phosphorylation of the cell adhesion molecule Arc-1/uvomorulin. Thus, scatter factor represents a clearly defined molecular species which induces, in vitro, the progression of epithelial cells to a more motile, i.e., invasive phenotype

Helium nanodroplet isolation ro-vibrational spectroscopy: methods and recent results

In this article, recent developments in HElium NanoDroplet Isolation (HENDI) spectroscopy are reviewed, with an emphasis on the infrared region of the spectrum. Topics discussed include experimental details, comparison of radiation sources, symmetry issues of the helium solvation structure, sources of line broadening, changes in spectroscopic constants upon solvation, and applications including formation of novel chemical structures.Comment: 24 pages, 8 figures, 3 tables; to be published in the Journal of Chemical Physic

Kosmische Strahlung

Das vorliegende Unterrichtsmaterial bietet Ihnen und Ihren Schülern Einblicke in das faszinierende Forschungsfeld der Astroteilchenphysik. Dabei steht die experimentelle Untersuchung von kosmischen Teilchen am Beispiel der Myonen im Vordergrund. In den KAPITELN 1 und 2 werden zunächst einige Hintergrundinformationen für Lehrkräfte, wie beispielsweise Anknüpfungspunkte an den Lehrplan, benötigte Vorkenntnisse der Schüler, Lernziele sowie fachliche und methodische Hinweise gegeben. KAPITEL 3 beschäftigt sich dann mit der kosmischen Strahlung an sich. Mit Hilfe der Betrachtung von Teilchen in einer Nebelkammer gelingt der Einstieg in das Thema der Astroteilchenphysik. Neben den Spuren bereits bekannter Teilchen wie z. B. Elektronen und Alpha-Teilchen begegnen den Schülern hier erstmalig auch Myonen. Mittels anderer Experimente werden diese dann genauer untersucht. Die Experimente und Fachtexte werden durch entsprechende Aufgaben ergänzt. Abschließend wird dann die Entstehung der Myonen thematisiert. In KAPITEL 4 finden sich die vollständigen Lösungen zu allen Aufgaben. KAPITEL 5 bietet einen Überblick über weiterführende Materialien zum Thema kosmische Strahlung