Crystallization of S-layer protein lattices on surfaces and interfaces

A review is given on the structure, chemistry, and assembly of crystalline bacterial cell surface layers (S-layers). S-layers composed of single protein or glycoprotein species represent the most common cell surface structures observed in prokaryotic organisms. Isolated S-layer proteins possess the intrinsic property for recrystallization into isoporous monomolecular arrays in suspension and at a broad spectrum of surfaces (e.g. silicon, metals, polymers) and interfaces (e.g. air–liquid interface or lipid films). The well-defined arrangement of functional groups on S-layer lattices allows the binding of functional molecules (e.g. enzymes, antibodies, ligands) and particles in defined regular arrays. S-layers also represent templates for the formation of inorganic nanocrystal superlattices (e.g. Au, CdS, Pt) as required for molecular electronics and non-linear optics. Finally, S-layers can be used as the structural basis for a biomolecular construction kit involving all major species of biological molecules for applications in molecular nanotechnology, nanobiotechnology and biomimetics.     

Optimierung eines laserunterstützten Wickelverfahrens für thermoplastische Prepregrovings mit Hilfe der statistischen Versuchsmethodik

Forschung im Ingenieurwesen - Mit Hilfe der statistischen Versuchsmethodik wird der laserunterstützte Wickelprozeß kohlenstoffaserverstärkter thermoplastischer Prepregrovings...     

Low Power Encoding Techniques for Dynamically Reconfigurable Hardware

In this paper, an approach to the implementation of digital systems is presented which utilizes dynamic hardware reconfiguration in order to automatically minimize the power dissipated on module interconnections such as system buses during system run time. Reduction of power dissipation is achieved by means of an activity-reducing system bus encoding technique. Encoder and decoder are implemented with dynamically reconfigured code tables which contain a transition minimizing code that is periodically recomputed during run time of the system in order to adapt to variations in the statistical parameters of the encoded data stream. We present the theoretical basics and an efficient implementation of a corresponding coder-decoder system. Experimental results showed a reduction in bus transition activity of up to 41%.     

Reductive transformations

Summary 2,3-Diheptyl- and 2,3,6,7-tetraheptyl-9, 10-anthraquinone are reduced to the corresponding diols and subjected to esterification with the chlorides derived from mono- and di-acids. The resulting polyesters are nicely soluble in organic solvents and can be characterized by vapor pressure osmometry and NMR spectroscopy.     

Energy policy scenarios to reach challenging climate protection targets in the German electricity sector until 2050

In this article we demonstrate how challenging greenhouse gas reduction targets of up to 95% until 2050 can be achieved in the German electricity sector. In the analysis, we focus on the main requirements to reach such challenging targets. To account for interdependencies between the electricity market and the rest of the economy, different models were used to account for feedback loops with all other sectors. We include scenarios with different runtimes and retrofit costs for existing nuclear plants to determine the effects of a prolongation of nuclear power plants in Germany. Key findings for the electricity sector include the importance of a European-wide coordinated electricity grid extension and the exploitation of regional comparative cost effects for renewable sites. Due to political restrictions, nuclear energy will not be available in Germany in 2050. However, the nuclear life-time extension has a positive impact on end consumer electricity prices as well as economic growth in the medium term, if retrofit costs do not exceed certain limits.     

Lutein and zeaxanthin in new dietary supplements—analysis and quantification

Lutein and zeaxanthin, two xanthophylls supposed to delay formation of age-related macular degeneration (AMD), are found in numerous new dietary supplements appearing on the international market. Usually, the lutein concentration ranges from 0.25 to 20 mg/serving size. The lutein contents of 14 products with lutein highlighted on the label were evaluated. Oily formulations were dissolved, and powdery capsule contents were extracted with solvents before high-performance liquid chromatography (HPLC) analysis (diode-array detector, 450 nm) using a C30 column. If lutein diesters from marigold (Tagetes erecta) were present, the extracts were saponified with methanolic KOH. To unequivocally identify carotenoids, HPLC-(atmospheric pressure chemical ionization)mass spectrometry was applied. In this study only all-trans-lutein was quantified, whereas cis isomers (approximately 1–5 area% of total lutein) were not taken into account. The lutein concentration of half of the products investigated was found to be below the amount stated, varying here from 11 to 93%. With the exception of one product, all dietary supplements contained zeaxanthin in amounts typical for the use of marigold oleoresin (6.0±1.4 area% of all-trans-lutein). The high discrepancy found between the amounts labeled and determined in half of the products may be attributed to degradation reactions or to improper storage conditions.     

Biochemical Characterization of Pyranose Oxidase from Streptomyces canus—Towards a Better Understanding of Pyranose Oxidase Homologues in Bacteria

Pyranose oxidase (POx, glucose 2-oxidase; EC 1.1.3.10, pyranose:oxygen 2-oxidoreductase) is an FAD-dependent oxidoreductase and a member of the auxiliary activity (AA) enzymes (subfamily AA3_4) in the CAZy database. Despite the general interest in fungal POxs, only a few bacterial POxs have been studied so far. Here, we report the biochemical characterization of a POx from Streptomyces canus (ScPOx), the sequence of which is positioned in a separate, hitherto unexplored clade of the POx phylogenetic tree. Kinetic analyses revealed that ScPOx uses monosaccharide sugars (such as d-glucose, d-xylose, d-galactose) as its electron-donor substrates, albeit with low catalytic efficiencies. Interestingly, various C- and O-glycosides (such as puerarin) were oxidized by ScPOx as well. Some of these glycosides are characteristic substrates for the recently described FAD-dependent C-glycoside 3-oxidase from Microbacterium trichothecenolyticum. Here, we show that FAD-dependent C-glycoside 3-oxidases and pyranose oxidases are enzymes belonging to the same sequence space.     

Machining of reproducible flaws corresponding to fatigue cracks for fracture mechanics tests of components and welded joints

In connection with the analysis and the development of failure concepts in fracture mechanics for quasistatic loaded components and elastic-plastic behaviour of the material, tests are also carried out with welded and/or complex shaped specimens or structures. Thereby the difficulty arises of generating reproducible flaws in the form of fatigue precracks in definite positions in the components, respectively in the welded joint. It is reported exemplarily about experiments on different CT25 and CCT specimens and on a pressure vessel which contained a fatigue pre-crack, a 0.2 mm saw cut or notches with notch root radius ≤ ≥ 0.1 mm as flaws. The comparison of the results with regard to J-integral at initiation of stable crack, J_i, and J_R curves shows that under certain conditions the 0.2 mm saw cut (notch root radius ≤ ≤ 0.02 mm) is a useful alternative, if reproducible generation of a fatigue pre-crack will not be successful or too expensive. The tests were carried out on StE 460 and on a welded joint of this steel at 25 ± 2°C.