Eine bakterielle Inaktivierung des Steroidhormons Ecdysteron

Aus einer wäßrigen Lösung des Crustaceenäautungshormons Ecdysteron wurden Bakterien in Reinkultur isoliert, die das Hormon abzubauen vermögen. Die mögliche Bedeutung der bakteriellen Inaktivierung des Ecdysterons wird diskutiert. A bacterium which is able to degrade the crustacean malting hormone ecdysterone was isolated from an aqueous solution of the hormone. The possible significance of this inactivation by bacteria is discussed

Point mutations of the human parathyroid calcium receptor gene are not responsible for non-suppressible renal hyperparathyroidism

Point mutations of the human parathyroid calcium receptor gene are not responsible for non-suppressible renal hyperparathyroidism. The calcium-dependent secretion of parathyroid hormone (PTH) is mediated through an extracellular G protein-coupled calcium receptor (CaR). Inactivating point mutations of this receptor have been found in familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. These diseases feature a decreased calcium sensitivity of the parathyroid glands, resulting in a rightward shift of the Ca2+-PTH relationship. Severe, non-suppressible renal hyperparathyroidism (rHPT) is often characterized by similar setpoint shifts to the right. Thus, point mutations of the CaR gene could contribute to non-suppressible rHPT. We examined genomic DNA of hyperplastic or mainly nodular tissues of 39 parathyroids from 25 rHPT-patients with resistance to calcitriol therapy. Amplification of the six exons of the CaR gene was followed by single-strand conformation polymorphism (SSCP) analysis. DNA sequencing was performed where band shifts were observed. No point mutations in the coding sequence of the CaR gene were detected using the PCR-SSCP strategy. Point mutations in the coding regions of the CaR gene probably play no role in the evolution of renal HPT and are not responsible for the calcitriol resistance of PTH secretion

The Chiral Switch of Metolachlor: The Development of a Large-Scale Enantioselective Catalytic Process

The development of an enantioselective catalytic process for the technical preparation of chiral agrochemicals is illustrated by the case history of the herbicide (S)-metolachlor (trade name Dual Magnum®). Four synthetic routes were investigated in some detail. The key step for the technical process of the enantiomerically enriched compound is the asymmetric hydrogenation of an imine intermediate made possible by a new iridium ferrocenyl diphosphine catalyst system. Using optimized conditions, the isolated imine can be hydrogenated at a hydrogen pressure of 80 bar and 50°C with a substrate-to-catalyst ratio of >1'000'000. Complete conversion is reached within 4 h with an enantioselectivity of 79% with an initial turnover frequency (tof) exceeding 1'800'000 h-1. This sets a new standard for the technical application of enantioselective catalysts. Important aspects and results for the different phases of the process development of the catalyst system as well as minimal prerequisites for the use of enantioselective catalysts for the production of agrochemicals are discussed

Synthesis and biological evaluation of some furanones as putative chitinase Inhibitors

Analogs of naturally occurring furanones that were reported to be weak inhibitors of Serratia marcescens chitinases were prepared and tested towards various chitinases. Some of these compounds - but not the natural products - were found to be weak but selective inhibitors; all glycosylated analogs tested were inactive. Activation of the plant enzyme hevamine was observed in one case, which is unusual

FAKULTÄT FÜR NATURWISSENSCHAFTEN

Herrn Prof. Dr. Klaus-Dieter Spindler betreut. TABLE OF CONTENT

der Universität

the immune system Analysis of signaling capacities of αPIX-/- and αPIX-/- βPIX +/- lymphocytes Generation of a βPIX conditional knockout DISSERTATION Zur Erlangung des Doktorgrades (Dr. rer. nat.) an der Fakultät für Naturwissenschafte

DYNAMIC INVESTIGATION OF POLYMERIC MATERIALS- REPRODUCIBLE DATA ACQUISITION AND PROFOUND MECHANICAL ANALYSIS

The investigation of the mechanical properties of surfaces has attracted increasing attention over the last decades. At the same time, miniaturization of mechanical devices such as MEMS- micro-electro-mechanical-systems- has reached nanoscale dimensions. By means of the Atomic Force Microscope (AFM), the mechanical properties at these lengthscales can be accessed. Theories and simulations describing these nano-mechanics, however, are not yet conclusive. The reliable and reproducible acquisition of AFM data has often been doubted, since the calculated results of the measurements did not fully comply with the results from macroscopic experiments. The AFM, however, is able to determine the mechanical behavior of surfaces reproducibly if the apparatus is calibrated thoroughly before and after the measurements are taken. With the Digital Pulsed Force Mode (DPFM) technique, it is possible to access the entire spectrum of sample dynamics and indentation behavior. Using a commercial setup and AFM tips, the mechanical properties of a dewetting polymer mixture of styrene-butadiene-rubber (SBR) and polymethylmethacrylate (PMMA) have been investigated. From the experiments, a recipe for the reliable acquisition of AFM data has bee