Redesigning the Active Site of Transaldolase TalB from Escherichia coli: New Variants with Improved Affinity towards Nonphosphorylated Substrates

Recently, we reported on a transaldolase B variant (TalB F178Y) that is able to use dihydroxyacetone (DHA) as donor in aldol reactions. In a second round of protein engineering, we aimed at improving the affinity of this variant towards nonphosphorylated acceptor aldehydes, that is, glyceraldehyde (GA). The anion binding site was identified in the X‐ray structure of TalB F178Y where a sulfate ion from the buffer was bound in the active site. Therefore, we performed site‐directed saturation mutagenesis at three residues forming the putative phosphate binding site, Arg181, Ser226 and Arg228. The focused libraries were screened for the formation of D ‐fructose from DHA and d,l ‐GA by using an adjusted colour assay. The best results with respect to the synthesis of D ‐fructose were achieved with the TalB F178Y/R181E variant, which exhibited an at least fivefold increase in affinity towards d,l ‐GA (K_M=24 mM ). We demonstrated that this double mutant can use D ‐GA, glycolaldehyde and the L ‐isomer, L ‐GA, as acceptor substrates. This resulted in preparative synthesis of D ‐fructose, D ‐xylulose and L ‐sorbose when DHA was used as donor. Hence, we engineered a DHA‐dependent aldolase that can synthesise the formation of polyhydroxylated compounds from simple and cheap substrates at preparative scale.     

High virus retention mediated by zirconia microtubes with tailored porosity

In this study the fabrication of zirconia microtubes for virus filtration using a sequence of slurry preparation, extrusion process, debinding and final sintering is presented. The sintered zirconia microtubes are characterised by microstructural analysis including Hg intrusion porosimetry, BET analysis and three-point bending tests. Zirconia microtubes sintered at 1050 °C are found to provide membrane properties featuring an open porosity of 50.7% with pore sizes in the range of 10–40 nm, a specific surface area of 23.2 m²/g and an average bending strength of 32.9 MPa, being suitable for virus filtration. Based on these mesoporous microtubes water permeate fluxes of 45 L/m² h are provided in dead-end filtration mode. A virus retention of 99.9999% (log reduction value of 6) for small bacteriophages MS2 and PhiX174 which served as surrogates for human pathogenic viruses is achieved in this study demonstrating a stable ceramic membrane with high viral retention properties.     

Some repeated goodness of fit tests when parameters are estimated

In the present paper the asymptotic distribution of repeated goodness of fit statistics, namely x^2_, likelihood ratio and cramér von Mises statistics for parametric families is derived under the nullhypothese as well as under contiguous alternatives. By introducing the notion of extende Landau symbolism the proofs for the limiting results for the non repeated versions are shown to carry over to the repeated versions straightforwardly.     

Effects of agronomic practices on the soil carbon storage potential in arable farming in Austria

According to the Kyoto-Protocol for carbon dioxide mitigation the direct human induced sequestration potential of carbon in agricultural soils may in the future be included for calculating net changes in greenhouse gas emissions. Therefore we used long-term experiments on arable land in Austria differing strongly in climate and soil conditions to explore the effects of agronomic practices on changes in soil organic carbon content. Optimal mineral N fertilizer input increased the carbon stocks on an average to 2.1 t ha⁻¹compared with no N fertilization in a 36 years period. Additional farm yard manure application (10 t ha⁻¹ y⁻¹) enhanced carbon storage to about 5.6 t ha⁻¹ after 21 years. Site-specific influences must be considered. Losses of 2.4 t carbon per ha were caused by additional irrigation of sugar beet and maize in a rotation with cereals in a 21 years period. The incorporation of all crop residues resulted in an increase of 3.4 t ha⁻¹ organic carbon in topsoil after 17 years. In the uppermost soil layer (0–10 cm) minimum and reduced tillage treatment enhanced carbon stocks to about 4.7 t ha⁻¹ and 3.2 t ha⁻¹ compared to conventional soil management within a decade. Based on these results, only a limited soil carbon sequestration potential can be inferred: Manuring and incorporation of crop residues are well-proven practices on arable land and therefore no additional human induced carbon sequestration might be achieved. The adoption of minimum tillage on Phaeozems, Chernozems and Kastanozems could, roughly calculated, result in a supplementary carbon storage of about 0.6% of the entire present annual carbon dioxide emission in Austria. However, the storage of carbon in topsoil means only a mid-term sequestration. By changing practices in short-terms, these amounts of carbon might be a source of additional carbon dioxide in the future. This revised version was published online in August 2006 with corrections to the Cover Date.     

Energetische Sanierung einer Kindertagesstätte in Plattenbauweise – Demonstrationsbauvorhaben “Plappersnut” in Wismar

Energy saving retrofitting of a prefabricated panel construction kinder‐garden – demonstration project “Plappersnut” in Wismar. The project “kindergarten Plappersnut” in Wismar focuses on cutting the energy consumption of the in 1972 build prefabricated plate construction down to one third by mainly 3 means: – improving the relation between building volume and outside surface by replacing the corridor building between the two main wings with a light membrane roof, covering the whole space, – eliminating energy loss through the building structure by coating the whole building with different isolation systems, – replacing all of the technical installation under the aspects of ecological energy supply and energy retrieving systems. The project was classed as a demonstration project of the EnSan‐Program, supported by the German Ministry for Economy and Technology.     

Numerische Modellierungen mit einem zyklisch‐viskoplastischen Stoffansatz für granulare Böden

Numerical modelling with a cyclic viscoplastic constitutive approach for granular soils. In modern Geotechnics, especially in track engineering, research for soil‐structure interaction under cyclic loading has been gaining importance over the past decades. Next to states of system/structure failure, the long‐term (deformation) behaviour is of major interest, as it has a major impact on e.g. maintenance costs in track engineering. Hence, the objective of this work is to be seen in the necessity of investigations on the long‐term deformation behaviour of granular soils and ballast under cyclic loading. In the present paper the validation and implementation of a cyclic viscoplastic constitutive approach for granular under cyclic dynamic loading, [1], into a numerical model is carried out. The investigation and set up of a theoretical and physical complete model has not been intended. The objective rather is the development of an engineering type model, appropriate for practical tasks. Some modelling examples are given to illustrate modelling capacities.     

Synthesis and Structure-Activity Relationship of Xenocoumacin 1 and Analogues as Inhibitors of Ribosomal Protein Synthesis

Ribosomal protein synthesis is an important target in antibacterial drug discovery. Numerous natural products have served as starting points for the development of antibiotics. We report here the total synthesis of xenocoumacin 1, a natural product that binds to 16S ribosomal RNA at a highly conserved region, as well as analogues thereof. Preliminary structure–activity relationship studies were aimed at understanding and modulating the selectivity between eukaryotic and prokaryotic ribosomes. Modifications were mainly tolerated in the aromatic region. Whole-cell activity against Gram-negative bacteria is limited by efflux and penetration, as demonstrated in genetically modified strains of E. coli. Analogues with high selectivity for eukaryotic ribosomes were identified, but it was not possible to obtain inhibitors selective for bacterial protein synthesis. Achieving high selectivity (albeit not the desired one) was thus possible despite the high homology between eukaryotic and prokaryotic ribosomes in the binding region.     

Alter Wein in neuen Schläuchen? Ethische Implikationen der Individualisierten Medizin

Definition of Problem In recent years, individualized medicine (IM) has become a buzz word in the academic as well as public debate surrounding health care. Like any technological development, however, it has (potential) ethical implications which have to be taken into account to enable an appropriate development and application of individualized preventive and therapeutic measures. Arguments An ethical assessment of IM poses several methodological challenges arising from the heterogeneity of the problem area as well as IM’s conceptual ambiguity and early stage of development. Against this background, we first specify the term IM to sharpen the context of our further considerations. On this basis we second present a heuristic typology of (possible) ethical implications of IM. Conclusion IM has potential ethical implications which mostly are well-known from other biomedical contexts. Moreover, these implications differ decisively with regard to different IM measures. On this account, an adequate ethical strategy requires evaluating each individualized approach separately.     

Reaktive Multischichtsysteme

Reactive Multilayer Systems as tailored heat sources for plastic bondings The use of reactive multilayer systems (RMS) as a heat source for the manufacturing of thermoplastic material bondings makes it possible to completely or partially overcome the limitations of conventional joining techniques, such as gluing or welding. The release of energy, which takes place directly inside the joining zone within milliseconds can be well adapted to the properties of the plastics. Thus undesired changes in the material structure of the joining partners can be avoided. Bonding strengths which are higher than or comparable to those of commercially used joining methods can be achieved. Furthermore, a particular advantage of RMS joining is that no surface pretreatment is required. RMS bondings of thermoplastics achieve high long-term stability for plastics, which themselves are only slightly susceptible to aging.