Cell‐Selective,Apoptosis‐inducing Rhodium(III) Crown Thiaether Complexes

Half‐sandwich rhodium(III) polypyridyl (pp) complexes with the metal atom capped by the facial crown thiaether 1,4,7‐trithiacyclononane [9]aneS₃ represent a promising class of apoptosis‐inducing potent cytostatic agents. The necrotic damage caused by the complexes is negligible. In vitro cytotoxicity assays with the human cancer cell lines MCF‐7 and HT‐29 and immortalized HEK‐293 cells indicate that the dicationic κ²N(imino) complexes [([9]aneS₃)RhCl(pp)]²⁺ are much more active than monocationic complexes [([9]aneS₃)RhCl₂(L)]⁺ (L=imidazole, CH₃CN). Whereas the κ²N(amino) complex [([9]aneS₃)RhCl(piperazine)]²⁺ is inactive, replacing piperazine with the structurally analogous κ²S (thiaether) ligand 1,4‐dithiane restores cytotoxicity as evidenced by IC₅₀ values in the range 8.1‐11.6 μM . Spectroscopic (CD, UV/Vis, NOESY) and viscosity measurements indicate that the active dppz complex 8 (IC₅₀ values: 4.7–8.9 μM ) exhibits strong intercalative binding towards DNA whereas the even more potent bipyrimidine complex 9 (IC₅₀ values: 0.6–1.9 μM ) causes no alteration of the duplex B conformation. Weaker intercalative binding is observed for the dpq complex 7 . A comparative annexin V–propidium iodide binding assay with lymphoma (BJAB) cells and healthy leukocytes demonstrates that the cytotoxic activity of complex 8 and particularly complex 9 is highly selective towards the malignant cells.     

A novel pyruvate kinase (PK-S) from boar spermatozoa is localized at the fibrous sheath and the acrosome

Boar spermatozoa contain a novel pyruvate kinase (PK-S) that is tightly bound at the acrosome of the sperm head and at the fibrous sheath in the principal piece of the flagellum, while the midpiece contains a soluble pyruvate kinase (PK). PK-S could not be solubilized by detergents, but by trypsin with no loss of activity. Purified PK-S as well as PK-S still bound to cell structures and soluble sperm PK have all kinetics similar to those of rabbit muscle PK-M1. The PK-S subunit had a relative molecular mass of 64 +/- 1 x 10(3) (n = 3), i.e. slightly higher than that of PK-M1, and carried an N-terminal extension (NH(2)-TSEAM-COOH) that is lacking in native PK-M1. Evidence is provided that PK-S is encoded by the PKM gene. Antibodies produced against the N-terminus of purified PK-S (NH(2)-TSEAMPKAHMDAG-COOH) were specific for PK-S as they did not react with somatic PKs or soluble sperm PK, while anti-PK-M1 recognized both sperm PKs. Immunofluorescence microscopy showed anti-PK-S to label the acrosome and the flagellar principal piece, whereas the midpiece containing the mitochondria was labelled only by anti-PK-M1. Immunogold labelling confirmed the localization of PK-S at the acrosome. In the principal piece, both polyclonal anti-PK-M1 and anti-PK-S were found at the fibrous sheath. Our results suggest that PK-S is a major component in the structural organization of glycolysis in boar spermatozoa.     

Concentration and distribution of heavy metals in urban airborne particulate matter in Frankfurt am Main, Germany

Heavy metal concentrations were measured in airborne dust collected at three sites with different traffic densities from August 2001 to July 2002 in the Frankfurt am Main area. Bulk samples of particulate matter (PM) with an aerodynamic equivalent diameter of <22 microm were collected on cellulose nitrate filters using air filtration devices. Fractionated samples of PM with an aerodynamic equivalent diameter of <10 microm were collected using an eight-stage Andersen impactor. Pb, Cd, Mn, Ni, Zn, V, As, Sb, Cu, Cr, Co, and Ce were determined by inductively coupled plasma sector field mass spectrometry, Pt and Rh were determined by adsorptive voltammetry, and Pd was determined by total reflection X-ray fluorescence analysis. The results show that the highest airborne heavy metal concentrations occurred at the main street with a large volume of traffic. With the exception of Co, V, Ce, and Mn, the heavy metals had an elevated enrichment factor compared to their concentrations in the continental crust. The main street site was especially contaminated with Sb, Zn, Cu, V, and Ni. Motor vehicles are the likely source of emissions. With the exception of Cr, Cu, and Zn, most of the airborne heavy metal concentrations determined for impactor samples deviate slightly from the results for total airborne dust. Heavy metal particle size distributions can be divided into three groups. For metals such as As, Cd, Pb, and V, the main fraction can be found in fine particles with a diameter of <2.1 microm, whereas Ce, Cr, Co, and Ni occur mainly in coarse particles with a diameter of >2.1 microm. Cu, Mn, Sb, Zn, Pt, Pd, and Rh occur in high concentrations in the medium range of the impactor stages (particle diameters of 1.1-4.7 microm). Metal concentrations in fine dust particles are needed to assess the human health risks of their inhalation.     

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Drop rise velocities and fluid dynamic behavior in standard test systems for liquid/liquid extraction—experimental and numerical investigations

The fluid dynamic behavior of single organic droplets rising in a quiescent ambient liquid is investigated experimentally and numerically. Three standard test systems for liquid/liquid extraction recommended by the European Federation of Chemical Engineering (EFCE) but without the respective transfer component have been chosen for the investigations: toluene/water, n-butyl acetate/water, and n-butanol/water, representing systems with high, medium, and low interfacial tension. Simulations are performed using the academic code Navier, which features a sharp interface representation and a variational formulation of the curvature. The validity of both correlations and the results obtained by dynamic numerical simulation is discussed in terms of terminal rise velocity, aspect ratio, and the onset of shape oscillation. The numerical results show excellent agreement with experiments in all three test systems, and with simulations in the n-butanol/water system published recently by Bertakis et al. (2010). The presented numerical method is applicable for a wide range of interfacial tension, whereas the investigated correlations lose accuracy with decreasing interfacial tension.     

Eine Stellungnahme zum Beitrag von Sass & Treskatis: “Herstellungs- und Bemessungsgrundlagen für einen verlaufsgesteuerten Trinkwasserbrunnen ...”

Ohne Zusammenfassung Eingang des Beitrages: 14.03.2000 / Eingang des überarbeiteten Beitrages: nicht überarbeitet, nur korrigiert     

n-Type Doping of Vapor–Liquid–Solid Grown GaAs Nanowires

In this letter, n-type doping of GaAs nanowires grown by metal–organic vapor phase epitaxy in the vapor–liquid–solid growth mode on (111)B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations N _D of GaAs nanowires are found to vary from 7 × 10¹⁷ cm^-3 to 2 × 10¹⁸ cm^-3. The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal–insulator-semiconductor field-effect transistor devices.     

Impact of Marangoni instabilities on the fluid dynamic behaviour of organic droplets

Marangoni instabilities in dispersed liquid/liquid systems occur if the local solute concentration varies over the interface. The additional shear stress at the interface between a droplet and an ambient phase generates complex convection patterns which increase temporarily the global drag coefficient of the drop and thus retard the drop rise velocity. When Marangoni effects get weaker, the shear forces decrease and the drop reaccelerates. In the present experimental study, the transient drop rise velocity has been intensely investigated in the system toluene_(d)/acetone_(s)/water_(c) for different initial solute concentrations and different drop diameters. Both mass transfer directions have been considered. The reacceleration time as an indicator of the end of Marangoni dominance can be expressed as a function of drop diameter and initial solute concentration.