Response of Kidney Tissue to Dynamical Loading

In shock-wave lithotripsy – a medical procedure to fragment kidney stones – the patient is subjected to hypersonic waves focused at the kidney stone. Although this procedure is widely applied, the physics behind this medical treatment, in particular the question of how the injuries of the surrounding kidney tissue arise, is still under investigation. Here we contribute to the solution of this problem with large scale numerical simulations of a human kidney under shock-wave loading. For this purpose we developed a complex constitutive model of the bio-mechanical kidney system. Assuming a multiplicative decomposition of the deformation gradient and adopting an internal variable formulation for the inelastic deformation the model is able to handle large deformations, time-effects, rate-sensitivity and material damage. By finite element simulations we study the shock-wave propagation into the kidney tissue and analyze the resulting stress states. Unknown material parameters are adapted and special attention is paid on the bubble expansion within the soft tissue. The numerical simulations predict localized damage in the human kidney within the focal region of the shock waves. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

High content screening for G protein-coupled receptors using cell-based protein translocation assays

G protein-coupled receptors (GPCRs) have been one of the most productive classes of drug targets for several decades, and new technologies for GPCR-based discovery promise to keep this field active for years to come. While molecular screens for GPCR receptor agonist- and antagonist-based drugs will continue to be valuable discovery tools, the most exciting developments in the field involve cell-based assays for GPCR function. Some cell-based discovery strategies, such as the use of beta-arrestin as a surrogate marker for GPCR function, have already been reduced to practice, and have been used as valuable discovery tools for several years. The application of high content cell-based screening to GPCR discovery has opened up additional possibilities, such as direct tracking of GPCRs, G proteins and other signaling pathway components using intracellular translocation assays. These assays provide the capability to probe GPCR function at the cellular level with better resolution than has previously been possible, and offer practical strategies for more definitive selectivity evaluation and counter-screening in the early stages of drug discovery. The potential of cell-based translocation assays for GPCR discovery is described, and proof-of-concept data from a pilot screen with a CXCR4 assay are presented. This chemokine receptor is a highly relevant drug target which plays an important role in the pathogenesis of inflammatory disease and also has been shown to be a co-receptor for entry of HIV into cells as well as to play a role in metastasis of certain cancer cells.     

Extraktionsverhalten methylsubstituierter chinolin-8-ole gegenüber kupfer

Extraction behavior of methyl-substituted 8-quinolinols towards copper). The distribution of 2-, 5-, and 7-methyl-8-quinolinols and the extraction of their copper chelates are reported for the chloroform/water system. The stability constants for the copper complexes were calculated. From the acidity and distribution constants of the isomeric 8-quinolinols and the stability and extraction constants of the copper chelates, 7-methyl-8-quinolinol provides the highest complex stability and is the best extractant of the series.     

Biosynthesis of cervimycin C, an aromatic polyketide antibiotic bearing an unusual dimethylmalonyl moiety

Cervimycin C is the major component of an antibiotic complex produced by Streptomyces tendae HKI-179 consisting of a tetracycline-type aglycon, six tridesoxysugars and a rare dimethylmalonyl moiety. The biosynthetic origin of cervimycin was studied by molecular studies and feeding experiments, which reveal that the dimethylmalonate unit is not derived from malonate, but from valine.     

Optical Stark effect in a quantum dot: ultrafast control of single exciton polarizations

We report the first experimental study of the optical Stark effect in single semiconductor quantum dots (QD). For below band gap excitation, two-color pump-probe spectra show dispersive line shapes caused by a light-induced blueshift of the excitonic resonance. The line shape depends strongly on the excitation field strength and is determined by the pump-induced phase shift of the coherent QD polarization. Transient spectral oscillations can be understood as rotations of the QD polarization phase with negligible population change. Ultrafast control of the QD polarization is demonstrated.     

Electronic photodissociation spectroscopy of Aun- x Xe (n = 7-11) versus time-dependent density functional theory prediction

Electronic (one-photon) photodepletion spectra were recorded for gold cluster anions complexed with one xenon atom over the photon energy range 2.1-3.4 eV. Clusters were generated by pulsed laser vaporization and probed under collisionless molecular beam conditions. The spectra obtained are highly structured with the narrowest features--assigned to individual electronic transitions--having bandwidths of less than 40 meV. Time-dependent density functional theory predictions of optically allowed transitions for the most stable--planar--isomers of the corresponding bare metal cluster anions are generally consistent with the experimental observation.     

Liquid crystalline paracyclophane derivatives

Various paracyclophane derivatives incorporating 4,4'-biphenyl, 2,5-diphenyl-1,3,4-thiadiazole, phenyl benzoate and 2,6-disubstituted naphthyl rigid cores were synthesized and their mesomorphic behaviour was studied using polarizing microscopy, DSC and X-ray diffraction. Most of these macrocyclic compounds possess liquid crystalline properties with unexpectedly high clearing temperatures compared to those of conventional calamitic mesogens. In this way, the coupling of two appropriate rigid units using flexible chains to form a macrocycle constitutes a new and powerful approach towards mesophase induction and stabilization. The types of mesophase formed by these macrocycles do not depend only on the nature of the bridging chains, but also strongly on the structure of the rigid aromatic system. The smectic A phase and the E phase are formed by polyetherbiphenylophanes. Poly-ethercyclophanes incorporating the 2,5-diphenylthiadiazole rigid core form nematic and smectic C phases. The nematic phase is the only mesophase when the rigid core is the phenyl benzoate unit. No mesomorphic properties could be detected for macrocycles which featured either the benzyl phenyl ether moiety or the 2,6-disubstituted naphthalene unit in their constitution.