Direkte fluorimetrische Bestimmung von 3,4-Benzpyren im w?\rigen Medium

Zusammenfassung Es wurde eine direkte Bestimmung des 3,4-Benzpyrens in wä\riger Lösung beschrieben, die auf der Löslichkeitserhöhung beruht, die das in Wasser schwer lösliche 3,4-Benzpyren durch Coffein erfährt. Es können so noch 4 ng/ml bei der angegebenen Standardisierung bestimmt werden. Bei der Direktbestimmung des 3,4-Benzpyrens im System Coffein-Wasser ist ein p_H >6,0 einzuhalten, da bei höheren Wasserstoffionenkonzentrationen die Fluorescenzintensität stark abnimmt.

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Direct fluorimetric determination of benzo(a)pyrene in aqueous medium

A method for the direct determination of benzo(a)pyrene in aqueous solution is based on the increase of its solubility by coffeine. 4 ng of benzo(a)pyrene/ml can be determined by the procedure described. In this direct determination in the system coffeine-water the p_H has to be adjusted to >6.0, as the fluorescence intensity considerably decreases with higher H⁺ concentrations.

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Eine ausführliche Darstellung findet sich in der Dissertation von G. Becker, Univ. Karlsruhe 1968.

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Die Messungen zu dieser Arbeit -wurden an dem Chemischen Untersuchungsamt für das Saarland, Saarbrücken, mit einem Spektralphotometer der Deutschen Forschungsgemeinschaft ausgeführt. Beiden Institutionen sind wir zu Dank verpflichtet.     

THE EFFECTS OF HOST-CELL REACTIVATION ON ASSAY OF U.V.-IRRADIATED HAEMOPHILUS INFLUENZAE TRANSFORMING DNA

Abstract— The host cell reactivation (HCR) mechanism in Haemophilus influenzae cells is inhibited by sub-microgram concentrations of acriflavine (as is already known to be true for Escherichia coli ). Exposure of these cells to similar concentrations of the drug during bacterial transformation increases the apparent ultraviolet light (u.v.) sensitivity of previously irradiated transforming DNA, indicating a repair of this DNA after uptake by the cells under normal conditions. Repair is inhibited by applying acriflavine at any time up to one hour after competent cells contact the irradiated transforming DNA. The fraction of the u.v. damage repaired by HCR is very different for different genetic markers. Those markers which are most u.v. sensitive when assayed in the absence of acriflavine are most poorly repaired, suggesting that this is the reason for their higher sensitivity. For all markers the fraction of the damage repairable by in vitro photoreactivation is approximately constant, and strongly overlaps the damage repairable by HCR. The degree of HCR achieved can be altered by experimental treatment of the H. influenzae DNA prior to transformation. Thus treatment of irradiated DNA with an enzyme from Micrococcus lysodeikticus –known to attack u.v. damaged, but not undamaged DNA–prevents subsequent intracellular repair of the same u.v. lesions whose repair is inhibited by acriflavine. Similarly, partial replacement of the thymine in transforming DNA by 5-bromouracil (BU) strongly inhibits repair of subsequent u.v. damage. As in bacteriophage, the BU effect is relieved if the u.v. exposure occurs in the presence of cysteamine. It is clear that intracellular repair must be considered in interpreting experiments with u.v.-irradiated transforming DNA.     

Austausch von Chrom(III) mit Chrom(II) und Szilard—Chalmers-Reaktion von Kaliumchromat

Zusammenfassung Durch Versuche mit⁵¹Cr wird gezeigt, daß Cr³⁺ mit Cr²⁺ austauscht, wenn man ein Chrom(III)-Salz in wässeriger Cr²⁺-Lösung auflöst, d. h. die Hydratation zum reaktionsträgen [Cr(H₂O)₆]³⁺ verläuft relativ langsam. Die Bedeutung dieses Austausches für dieSzilard—Chalmers-Reaktion von Chromat wird diskutiert.

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Experiments with⁵¹Cr prove the exchange of Cr³⁺ with Cr²⁺ when a Cr(III)-salt is dissolved in an aqueous solution of Cr²⁺. This indicates that the hydration to the inert [Cr(H₂O)₆]³⁺ is relatively slow. The importance of this exchange for theSzilard—Chalmers reaction of chromate is discussed.

     

Treatment of cutaneous T cell lymphoma with extracorporeal photopheresis induces Fas-ligand expression on treated T cells,but does not suppress the expression of co-stimulatory molecules on monocytes

Following extracorporeal photopheresis (ECP), lymphocytes become apoptotic and upregulate class I MHC antigenic peptides. Conversely, ECP treated monocytes demonstrate activation markers and have an increased avidity for the phagocytosis of apoptotic T cells. Processing of apoptotic T cells by monocytes, following ECP, is thought to induce an immunomodulatory response, which targets untreated, but clonal T cells. Recently we detected apoptotic lymphocytes immediately post ECP. Although enhanced CD95 (Fas) expression has been observed 24 h post ECP, CD95 and Fas-ligand (Fas-L) expression have not been determined at this very early apoptotic stage. Exposure of monocytes to UV has previously suppressed expression of the co-stimulatory molecules required for the presentation of processed antigens to T cells. Our data demonstrate no increase in CD95 or Fas-L expression on T cells tested immediately following ECP. However, the number of T cells expressing Fas-L significantly increased 24 h post ECP (P<0.005). The expression of the co-stimulatory molecules, CD54, CD80 and CD86, remained unaltered on monocytes treated by ECP. Although the mechanism responsible for early induction of lymphocyte apoptosis remains unclear, the later apoptosis involves Fas-L expression. The maintenance of co-stimulatory molecules, on treated monocytes, indicates that they retain the ability to induce an immunomodulatory response.     

Dimethylzinc-mediated addition of alkenylzirconocenes to alpha-keto and alpha-imino esters

[reaction: see text] Hydrozirconation of alkynes followed by in situ transmetalation to dimethylzinc and 1,2-addition to activated ketones and N-diphenylphosphinoylimines leads to tertiary allylic alcohols and amines in high overall yield. With 8-phenylmenthol as the chiral auxiliary, si-face attack proceeds in good to excellent diastereoselectivities.     

Catalytic Titrations of Silver(I) Using an Iodide-Catalyzed Mn(IV)-As(III) Indicator Reaction in the Presence of Sulfuric Acid with Detecting the End-Point by Methods with Two Polarized Electrodes

Catalytic bipotentiometric and biamperometric methods for determining silver(I) with the use of the new manganese(IV)-arsenic(III) indicator reaction catalyzed by iodide ions in the presence of sulfuric acid have been developed. The effects of the sulfuric acid concentration of some ionic species, of the mole ratio of manganese(IV) to arsenic(III) in the solution titrated, and of the titrand temperature, as well as of the current and potential difference, respectively, used for polarization of the indicator electrodes on the conditions for determinations of silver(I) of various concentrations were investigated. The error in the determination of 1.0 g/cm³ silver(I) do not exceed 2%, and the precision of the results is high for both methods.     

Cellular adhesion and proliferation on poly(3,4-ethylenedioxythiophene): Benefits in the electroactivity of the conducting polymer

Cell adhesion and proliferation in poly(3,4-ethylenedioxythiophene), an electroactive polythiophene derivative generated by anodic polymerization, has been investigated. Results show that epithelial cells Hep-2 present significant activity on the surface of poly(3,4-ethylenedioxythiophene) electrodeposited on stainless steel electrodes, no sign of cytotoxicity being detected for this conducting polymer. Indeed, seeded and cultured cells bound better to poly(3,4-ethylenedioxythiophene) than to uncoated stainless steel, the latter substrate being used as a control. Furthermore, the electrochemical characteristics of poly(3,4-ethylenedioxythiophene) covered with cells was determined in different biological media using cyclic voltammetry experiments. Results reveal a significant increase in the electroactivity of this material when it is covered with a cellular monolayer. The overall of the results evidences not only the biocompatibility of poly(3,4-ethylenedioxythiophene) with Hep-2 cells but also their electrocompatibility.     

k0-measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

Recommended k₀-factors and related nuclear data for use in (n, γ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k₀ standardization method are reviewed. For convenient data reduction, computer programs were developed.     

Synthesis, band structure, and optical properties of Ba2ZnV2O8

A novel compound Ba₂ZnV₂O₈ has been synthesized in high temperature solution reaction and its crystal structure has been characterized by means of single crystal X-ray diffraction analysis. It crystallizes in monoclinic system and belongs to space group P2₁/c with a=7.9050(16), b=16.149(3), , β=90.49(3). It builds up from 1-D branchy chains of [ZnV₂O₈⁴⁻]_∞, and the Ba²⁺ cations are located in the space among these chains. The IR spectrum, ultraviolet-visible diffuse reflection integral spectrum and fluorescent spectra of this compound have been investigated. The calculated results of energy band structure by the density functional theory method show that the solid-state compound of Ba₂ZnV₂O₈ is an insulator with direct band gap of 3.48 eV. The calculated total and partial density of states indicate that the top valence bands are contributions from the mixings of O-2p, V-3d, and Zn-3d states and low conduction bands mostly originate from unoccupied antibonding states between the V-3d and O-2p states. The V-O bonds are mostly covalence characters and Zn-O bonds are mostly ionic interactions, and the ionic interaction strength is stronger between the Ba-O than between the Zn-O. The refractive index of n_x, n_y, and n_z is estimated to be 1.7453, 1.7469, and 1.7126, respectively, at wavelength of 1060 nm for Ba₂ZnV₂O₈ crystal.     

Untersuchung der Temperaturabhängigkeit derg ik -Tensoren von Polyäthyleneinkristallen

Zusammenfassung Es wurden die Kristallitgröße und die Änderungen der parakristallinen Gitterstörungen aus den Linienbreiten des Röntgenweitwinkeldiagramms von lösungskristallisiertem linearem Polyäthylen bei den Temperaturen 15°K, 73°K, 173°K und Zimmertemperatur bestimmt. Es wurde eine Zunahme der Gitterstörungen mit fallender Temperatur gefunden.

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Summary The crystallite size and the paracrystalline distortions in polyethylene single crystals were evaluated by the measurement of the linewidth in the X-ray wide angle diagram at four different temperatures (15°K, 73°K, 173°K and 297°K). An increase of the lattice distortions with decreasing temperature was found.

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Mit 3 Abbildungen

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.