Initial Molecular Recognition Steps of McjA Precursor during Microcin J25 Lasso Peptide Maturation

Microcin J25 (MccJ25) has emerged as an excellent model to understand the maturation of ribosomal precursor peptides into the entangled lasso fold. MccJ25 biosynthesis relies on the post‐translational modification of the precursor McjA by the ATP‐dependent protease McjB and the lactam synthetase McjC. Here, using NMR spectroscopy, we showed that McjA is an intrinsically disordered protein without detectable conformational preference, which emphasizes the active role of the maturation machinery on the three‐dimensional folding of MccJ25. We further showed that the N‐terminal region of the leader peptide is involved in interaction with both maturation enzymes and identified a predominant interaction of V43–S55 in the core McjA sequence with McjC. Moreover, we demonstrated that residues K23–Q34 in the N‐terminal McjA leader peptide tend to adopt a helical conformation in the presence of membrane mimics, implying a role in directing McjA to the membrane in the vicinity of the lasso synthetase/export machinery. These data provide valuable insights into the initial molecular recognition steps in the MccJ25 maturation process.     

Universitärer Forschungscluster „Sustainable Technologies in Metal Production and Processing” (STMP)

Foundation of a university research cluster — Co-operation along the value creation chain from raw materials to components — Evidence of joint performance offers — Utilization of synergies — Integration of Christian Doppler Laboratories — Flexible arrangement of co-operations and networks     

Crystallization of poly(ethylene terephthalate)/polycarbonate blends. I. Unreinforced systems

The crystallization and transition temperatures of poly(ethylene terephthalate) (PET) in blends with polycarbonate (PC) is considered using thermal analysis. Additives typically used in commercial polyester blends, transesterification inhibitor and antioxidant, are found to enhance the crystallization rate of PET. Differential scanning calorimetry (DSC) reveals two glass transition temperatures in PET/PC blends, consistent with an immiscible blend. Optical microscopy observations are also consistent with an immiscible blend. Small shifts observed in the T_g of each component may be due to interactions between the phases. The degree of crystallinity of PET in PET/PC blends is significantly depressed for high PC contents. Also, in blends with PC content greater than 60 wt %, two distinct crystallization exotherms are observed in dynamic crystallization from the melt. The isothermal crystallization kinetics of PET, PET modified with blend additives, and PET in PET/PC blends have been evaluated using DSC and the data analyzed using the Avrami model. The crystallization of PET in these systems is found to deviate from the Avrami prediction in the later stages of crystallization. Isothermal crystallization data are found to superimpose when plotted as a function of time divided by crystallization half-time. A weighted series Avrami model is found to describe the crystallization of PET and PET/PC blends during all stages of crystallization. © 1996 John Wiley & Sons, Inc.     

Technology Assessment on Renewable Raw Materials: Potentials and Risks of the Use of Starches

Starch as a renewable raw material for chemical/industrial uses has a long tradition. In terms of quantity, starch ranks third behind wood and vegetable oils. In the medium term, this position will be maintained, if not improved. The volume of renewable raw materials used for fuel is even greater and expected to increase in the medium term. By means of a technology assessment on chemical/industrial and energy uses of renewable raw materials, it shall be demonstrated where the specific potentials and risks of starch use can be found. Among others, the following aspects are considered: energy and CO₂ balance sheets, biodegradability and competiveness. Under the headings of „saving of raw materials (degree of self-sufficiency)”︁, „area required (reduction of surpluses)”︁, „employment effects”︁, „contribution to CO₂ reduction”︁ and „need for subsidies”︁, medium-term (up to 2005) potential use of starch in Germany is studied relative to use of renewable raw materials in total.     

H3PW12O40 acid dispersed on its Cs salt: improvement of its catalytic properties by mechanical mixture and grinding

Acidic cesium salts Cs_x H_3-xPW₁₂O₄₀ have been prepared by grinding together amounts of H₃PW₁₂O₄₀ and porous Cs₃PW₁₂O₄₀ compounds in varying stoichiometries. It is shown that this procedure leads to a dispersion of the acid on top of the high surface area Cs₃PW₁₂O₄₀ salt (160 m² g^-1), and, subsequently, yields high surface area materials which exhibit a much higher catalytic activity for n-butane isomerisation at 473 K when compared with samples prepared directly by chemical precipitation. This improvement holds particularly true with low Cs content (x < 2). This revised version was published online in July 2006 with corrections to the Cover Date.     

Long‐term testing of a high temperature polymer electrolyte membrane fuel cell: The effect of reactant gases

The investigations have been conducted with different oxidants and fuels with the aim of determining the state‐of‐the‐art of commercially available high temperature polymer electrolyte fuel cells based on polybenzimidazole for its application in combined heat and power generation systems. The fuel cell test performed with synthetic reformate (?63 μV/h) showed an increase of anode charge and mass transfer resistances. This behavior has suggested that CO may be generated from the CO₂ included in the synthetic reformate via reverse water gas shift reaction. The fuel cell test performed with pure O₂ developed the highest degradation rates (?70 μV/h) due to fast oxidative degradation of membrane electrode assembly materials such as cathode catalyst and membrane. Fuel cell operation with H₂/air exhibited the lowest degradation rates (?57 μV/h) and it requires longer investigating times to identify the different degradation mechanisms. Moreover, fuel cell tests performed with air suggested longer break‐in procedures to complete catalyst activation and redistribution of electrolyte. © 2015 American Institute of Chemical Engineers AIChE J, 62: 217–227, 2016     

CeO2−CoO Phase Diagram

Phase equilibria in the CeO₂−CoO system at temperatures above 1500°C were investigated. The microstructures and the phase compositions of the DTA (differential thermal analysis) samples and the quenched solid pellets were analyzed using SEM (scanning electron microscope), EDX (energy dispersive X-ray), and WDX (wavelength dispersive X-ray). A eutectic reaction was found at 1645 ± 5°C. The eutectic point was calculated to be at 82 ± 1.5 mol% CoO. The eutectic phases were the CeO₂-rich phase (containing <5 mol% CoO) and the CoO-rich phase (containing ∼0.5 mol% CeO₂). At 1580°C, the solubility of CoO in CeO₂ was ∼3 mol%.