Micro-thermal analysis (μTATM) is a technique in which thermal analysis is performed on surfaces of test specimens on a small (ca. 2×2 μm) scale. Like
any thermal analysis technique, interpretation of results benefits from accurate temperature information and knowledge of
the precision of the resultant measurement. However, temperature calibration for such methods is more challenging than with
its macro relatives since the calibrant comes into direct contact with the AFM sensor. This paper describes suitable calibration
procedures for different types of transitions namely for first order transitions (melting points) and for glass transition
temperatures using organic chemicals and polymers.
The photolysis of W(CO)6in CH2Cl2 produces (CO)5WCH2Cl2. The high reactivity of (CO)5WCH2Cl2 (1) was exploited to synthesize a vinylidene complexes via the acetylene-vinylidene rearrangement. The addition of a terminal
acetylene (H-C≡C-COOCH3) to a solution of (1) produced the η2-acetylene-pentacarbonyltungsten complex (CO)5W(η2-HC≡C-COOCH3) in good yield. The production of the vinylidene complex (CO)5W=C=CH-COOCH3in equilibrium with the acetylene complex in the reaction medium was verified experimentally by reaction with excess imine.
The heterocyclic organometallic compound of tungsten obtained was separated and purified and its structure was studied by
IR, 1H NMR, 13C NMR and mass spectrometry in comparison with the thermal analysis and elemental analysis data. The final aim of this investigation
is the development of a new alternative route to a β-lactame with antibacterial activity.
Authors:S. Fischer, R. Dreyer, H. Hussein, M. Weber, and H. Hartmann
The formation of cationic astatine /I/-coordination compounds with selenium-containing neutral ligands is described. The detection of compound formation and first physico-chemical data on the characterization of this new group of At/I/-compounds were obtained by investigation of their electromigration behaviour in free electrolytes. Se-donors coordinate more strongly to At/I/ than ligands containing carbamide and thiocarbamide. This fact is proved by electromigrational studies on the exchange of N,N-ethyleneselenocarbamide, respectively N,N-ethylenethiocarbamide with iodide.
Authors:A. Almási, Sz. Bojcsev, T. Fischer, H. Simon, P. Perjési, and Emil Fischer
The aim of these experiments was the investigation of the correlation between the metabolic enzyme activities and the intestinal and hepatic excretion of p-nitrophenol (PNP) and its metabolites (PNP-glucuronide: PNP-G and PNP-sulfate: PNP-S) in the same group of rats (n = 10). A jejunal loop was perfused with isotonic medium containing PNP in a concentration of 500 μM. The samples were obtained from the luminal perfusion medium and from the bile. For enzyme assays tissue samples were obtained from the liver and jejunum at the end of experiments. Significant differences were calculated by the Student’s t-test. The activity of UDP-glucuronyltransferase and sulfotransferase was about three times higher in the liver than in the small intestine. The activity of the ß-glucuronidase was about six times higher, the activity of the arylsulfatase was approximately seven times greater in the liver than in the jejunum. No significant difference was found between the luminal appearance and the biliary excretion of PNP-G. Contrary to these findings, the biliary excretion of PNP-S was significantly higher than the luminal appearance of PNP-sulfate. It can be concluded that no direct correlation exists between the activity of metabolic enzymes and the excretion rate of PNP-metabolites in the liver and in the jejunal segment of the small intestine.
Authors:R. Ludwig, S. Fischer, H. Hussein, M. Frind, and R. Dreyer
The ion mobilities of [211At] At(I) in dependence on thiourea (tu) concentration, iodide concentration and a mixture of both ligands were measured by the electromigration method in free electrolytes. An equilibrium model was developed for the characterization of electromigration curves which permitted the calculation of stability constants and ion mobilities of the complexes [AtI], [AtI2]–, [Attu]+, [Attu2]+ and [AtItu] existing in these solutions. Ethanol and water served as solvents. The temperature was 298 K and the ionic strength was about 0.05 mol/dm3.
Authors:R. Dreyer, I. Dreyer, S. Fischer, H. Hartmann, and F. Rösch
The formation of cationic astatine compounds with thiourea, thiourea derivatives and some N-acylthioureas was investigated in aqueous solutions. The ion mobilities in free electrolytes were determined for the detection of carrier-free astatine compounds and their characterization. Informations about the stability of this group of compounds could be given after investigations in the presence of halogenide and pseudo halogenide ions /Cl–, Br–, I–, SCN–/. First results on the reaction of At//+ with thiourea derivatives and N-acylthioureas in acid and neutral solutions are reported. The cationic astatine compound formation with representatives of this group is shown.
Authors:S. Bojcsev, A. Almási, H. Simon, P. Perjési, and Emil Fischer
In the extrahepatic drug metabolism the intestinal tract can play an important role. These experiments were designed to study the biotransformation of p-nitrophenol (PNP) in the small intestine in the rat. Various segments of the small intestine (proximal and distal jejunum, terminal ileum) were perfused with isotonic solution in vivo containing different concentrations of PNP (20–100–500–1000 μM) and the concentrations of metabolites (PNP-G: p-nitrophenol glucuronide, PNP-S: p-nitrophenol sulfate) were determined in the perfusion medium. It was found a decreasing tendency in the glucuronidation from the proximal to distal segment of the small intestine: e.g. 430 nmol, 240 nmol, and 100 nmol PNP-G appeared in the perfusion medium in the proximal, distal jejunum and in the terminal ileum, respectively, when 500 μM PNP was luminally perfused for 90 minutes. Similar ratio was found at the luminal perfusion of other PNP-concentrations, too. Luminal appearance of sulfoconjugate of PNP was considerably lower and no clear gradient tendency in the formation of PNP-S could be detected in the small intestine from the proximal to distal segment. Our results show that there are considerable differences in drug metabolism in various segments of the small intestine. We have found a gradient conjugating activity from proximal to distal segment of small intestine in the glucuronidation of PNP.
Authors:J. H. Fischer, C. F. McCauley, D. P. Armstrong, I. Debski, and H. U. Wittmer
Seabirds are considered ecosystem engineers, because they facilitate ecosystem functioning (e.g., nutrient cycling), crucial for other marine and terrestrial species, including reptiles. However, studies of seabird-reptile interactions are limited. Here, we assessed the influence of the ‘Critically Endangered’ Whenua Hou Diving Petrel (Pelecanoides whenuahouensis) on the occurrence of two threatened skinks, Stewart Island green skink (Oligosoma aff. chloronoton) and southern grass skink (O. aff. polychroma). We surveyed skinks for 26 consecutive days at 51 sites with and 48 sites without Diving Petrel burrows in the dunes on Codfish Island (Whenua Hou), New Zealand. We used occupancy modelling to assess the influence of burrows on the occurrence of skinks, while accounting for other factors affecting occupancy (Ψ) and detection probabilities (p). Diving Petrel burrows had a contrasting effect on the occurrence of skinks. On average, Ψ̂ of Stewart Island green skinks was 114% higher at sites with burrows compared to sites without, while Ψ̂ of southern grass skinks was only 2% higher. Occurrence of both skinks was negatively influenced by the presence of the other skink species. On average p̂ were low: 0.013 and 0.038 for Stewart Island green and southern grass skinks, respectively. Stewart Island green skinks appear attracted to burrows, which might facilitate thermoregulation (i.e., shelter from temperature extremes). The larger Stewart Island green skinks may subsequently exclude the smaller southern grass skinks at burrows, causing the contrasting relationships. We suggest that these interspecific interactions should be considered when implementing conservation management, e.g., through the order of species reintroductions.
Authors:D. Schumann, St. Fischer, St. Taut, A. Novgorodov, R. Misiak, N. Lebedev, and H. Bruchertseifer
The sorption behavior of microamounts of Hf and Ta on DOWEX 50×8 and DOWEX 1×8 from aqueous HCl/HF solutions has been investigated. Suitable separation conditions for these two elements on cation exchange resins were found in solutions containing 1.5M HCl/10–4M HF and 0.05M HCl/10–3M HF. Kinetic experiments showed that the system can be applied in high speed on-line separations.
Authors:Markus M. Heimesaat, Andreas Kupz, André Fischer, Dietrich H. Nies, Gregor Grass, Ulf B. Göbel, and Stefan Bereswill
Escherichia coli K12 (EcK12) is commonly used for gene technology purposes and regarded as a security strain due to its inability to adhere to epithelial cells. The conventional intestinal microbiota composition is critical for physiological colonization resistance against most bacterial species including pathogens. We were therefore interested whether intestinal colonization by a genetically modified EcK12 (W3110) strain carrying a chloramphenicol resistance cassette was facilitated following broad-spectrum antibiotic treatment eradicating the intestinal microbiota or induction of small intestinal inflammation accompanied by distinct microbiota shifts. Whereas conventional C57BL/6 and BALB/c mice had virtually expelled the EcK12 (W3110) strain within the first 3 days upon peroral infection, EcK12 (W3110) could establish within the small and large intestines of gnotobiotic mice generated by quintuple antibiotic treatment. Gnotobiotic mice perorally infected with EcK12 (W3110) plus fecal transplant from conventional donors harbored lower intestinal EcK12 (W3110) loads compared to animals challenged with EcK12 (W3110) alone. Furthermore, EcK12 (W3110) infection of conventional mice after but not before induction of ileitis resulted in stable colonization of ileum and colon by EcK12 (W3110). Taken together, broad-spectrum antibiotic treatment and intestinal inflammation compromise colonization resistance and thus facilitate colonization of the intestinal tract with genetically modified EcK12 security strains.