The behaviour of the AsCo3(CO)9 cluster as a ligand for Cr,Mo, W,and Fe carbonyls and AlCl3

Summary The n-donor character of the AsCo₃(CO)₉ cluster has been tested by reacting it with soft (metal carbonyls) and hard (AlCl₃) Lewis acids. The (CO)_xMAsCo₃(CO)₉ compounds (with M=Cr, Mo or W, x=5; M=Fe, x=4) and Cl₃Al AsCo₃(CO)₉ have been prepared.     

Darstellung,kristallographische Daten und IR-Spektrum von Mangan(II)-diarsenat

Mn₂As₂O₇ has been obtained by solid state reaction between As₂O₅ and MnCO₃ at 600 °C and also by thermal decomposition of NH₄MnAsO₄·H₂O. The crystallographic study has shown that the substance crystallizes in the monoclinic thortveitite structure. Its i.r. spectrum was recorded and discussed in relation with their structural properties. The i.r. spectrum of the parent compound NH₄MnAsO₄·H₂O was also briefly discussed.

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Hydrogen transfer reactions catalyzed by neutral rhodium(I) Schiff base complexes

Summary Hydrogen transfer reactions from 2-propanol to acetophenone or cyclohexene are catalyzed by neutral rhodium(I) complexes of the type [Rh(COD)L] and [Rh₂(COD)₂L] (where L and L are Schiff base ligands and COD=cycloocta-1,5-diene). Some dependency of the catalytic activity on the electronic and steric properties of the ligands are discussed.     

EAL interlaboratory comparison Wa1 – Testing of potable water

 The accreditation of laboratories has emphasized the use of interlaboratory comparisons as a tool to monitor the comparability and accuracy of results laboratories produce. An interlaboratory comparison for water laboratories was organized among European Cooperation for Accreditation (EA) member countries; 30 laboratories, 7 of which were not accredited, from 14 European countries participated in this intercomparison. All the laboratories were chosen by the appropriate national accreditation bodies, with the instruction to select as participants those laboratories which act as national reference laboratories in this field. About 90% of the data collected was considered satisfactory after statistical treatment. Non-accredited laboratories performed as well as accredited laboratories. The laboratories were asked to take corrective action and report the corrections to the accreditation bodies. A great variation in the reported uncertainties of the results was observed. There seems to be a need to organize EA interlaboratory comparisons for national reference laboratories analysing water. It is obvious that even reference laboratories need training in how to estimate the uncertainty of results. Received: 22 July 1998 · Accepted: 21 September 1998     

PHOTOTOXICITY INDUCED BY HEMATOPORPHYRIN DERIVATIVE IN C5-DEFICIENT, MAST CELL-DEFICIENT AND LEUKOPENIC MICE

Abstract— The phototoxic response induced by hematoporphyrin derivative and irradiation was evaluated in mice congenitally deficient in the fifth component of complement (C5), those congenitally deficient in mast cells, and in cyclophosphamide-treated, leukopenic mice. Hematoporphyrin derivative, 10 mg/kg, was injected intraperitoneally, and 6 h later, the animals were irradiated (6.5 kj/m² at396–407 nm). Phototoxicity was quantified by measurement of the increase in ear-thickness. In control mice, at the end of the irradiation (0 h), an increase in the ear-thickness of28–37% was noted; it reached a peak of51–81 % at 24 h. The phototoxic response in C5-deficient mice was markedly suppressed both at 0 h and at 24 h ( P vs control, < 0.02 and < 0.05, respectively), while mast cell-deficient mice has a suppressed response at 24 h ( P vs control, < 0.001). In both groups of mice, the intensity of dermal mononuclear and polymorphonuclear infiltrates was not different from that of the respective controls. The response in leukopenic mice was suppressed at both 24 h and 48 h ( P < 0.001). These results indicate that intimate and complex interactions among the complement system, mast cells, and leukocytes are necessary for the complete manifestation of the phototoxic response.     

PUVA Treatment Selectively Induces a Cell Cycle Block and Subsequent Apoptosis in Human T-Lymphocytes

Psoralen plus UVA (320–400 nm radiation; PUVA) is a highly effective therapy for cutaneous diseases caused by skin infiltration with normal or neoplastic T-lympho-cytes. In comparing the effects of pharmacologically relevant, low-dose PUVA treatment on growth of human keratinocytes, peripheral blood leukocytes (PBMC), and T-lymphocyte cell lines, we determined that PBMC or T-lymphocytes were >50-fold more sensitive to cytotoxic effects of PUVA, while antiproliferative effects were produced by similar PUVA levels in all cell types. Low doses of PUVA (10 ng/mL 8-methoxypsoralen and 1–2 J/cm²) were highly cytotoxic for phytohemagglutinin-activated normal lymphocytes or transformed T-lymphocytes as assessed by two viability assays and by flow cytofluo-rometry. Altered lymphocyte morphology, nuclear fragmentation, TUNEL+ nuclei or nuclear fragments, and the appearance of a sub-G, DNA peak indicated that cell death occurred by apoptosis, beginning about 1 day after PUVA treatment and continuing for several days thereafter. From assessment of cell cycle progression in mi-mosine-synchronized cells, PUVA treatment markedly slowed cell cycle progression, eventually producing cell cycle arrest and apoptotic entry. We propose that the probable basis for disease remissions (psoriasis, cutaneous T-cell lymphoma) produced by PUVA treatment is through selective cytotoxic effects on clonal T-lymphocyte populations that are concentrated in diseased skin.     

Dinuclear asymmetric ruthenium complexes with 5-cyano-1,10-phenanthroline as a bridging ligand

New dinuclear asymmetric ruthenium complexes of the type [(bpy)(2)Ru(5-CNphen)Ru(NH(3))(5)](4+/5+) (bpy = 2,2'-bipyridine; 5-CNphen = 5-cyano-1,10-phenanthroline) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. The structure of the cation [(bpy)(2)Ru(5-CNphen)Ru(NH(3))(5)](4+) has been determined by X-ray diffraction. The mononuclear precursor [Ru(bpy)(2)(5-CNphen)](2+) has also been prepared and studied; while its properties as a photosensitizer are similar to those of [Ru(bpy)(3)](2+), its luminescence at room temperature is quenched by a factor of 5 in the mixed-valent species [(bpy)(2)Ru(II)(5-CNphen)Ru(III)(NH(3))(5)](5+), pointing to the occurrence of intramolecular electron-transfer processes that follow light excitation. From spectral data for the metal-to-metal charge-transfer transition Ru(II) --> Ru(III) in this latter complex, a slight electronic interaction (H(AB) = 190 cm(-1)) is disclosed between both metallic centers through the bridging 5-CNphen.     

Synthesis, structure and chiroptical properties of isoxazolidin-5-ones

Several isoxazolidin-5-ones were synthesized in an addition — rearrangement reaction from corresponding sugar lactones and hydroxylamines. The sign of the Cotton effect at ca. 220 nm can be correlated to the absolute configuration of the stereogenic center at C3 and can be predicted by Weigang's sector rule. X-ray diffraction study performed for 11 and 12 confirms the configuration at C3 to be 3S and 3R, respectively.     

A Calibration‐Base Method for the Evaluation of the Detection Limit of an Electrochemical Biosensor

The method based on the confidence limits of a regression straight line is applied to the linear portion of the calibration curve of a biosensor in order to determine the limit of detection. A practical application gives a detection limit of an ethanol biosensor greater than that calculated by using the method of the signal‐to‐noise‐ratio, S/N=3, but the value is more reliable because it accounts for the variability in the response at analyte additions. A simple approximation of the method is also presented.     

Ion-Exchange equilibria in cationic polyelectrolytes

A method which allows the evaluation of phenomenological ion exchange constants K_ex is proposed and tested in a cationic polyelectrolyte system. Results for nitrate/chloride exchange are nearly constant over the entire concentration range studied. However, for nitrate/bromide exchange, the results depend on the polyelectrolyte concentration, with K_ex following the same trend as the mean activity coefficient for the polyion bromide. For polyion fluoride, a conformational change is probably induced as nitrate is added to the solution and the result deviates from the linear relationship predicted by the method. Benzene sulfonate behaves like a hydrophilic anion, whereas tosylate and ethylbenzene sulfonate also induce conformational changes by hydrophobic interactions. These results are supported by viscosity measurements and agree well with those recently reported by Satoh, who considered changes in apparent molar volume. © 1994 John Wiley & Sons, Inc.