Schwermetallmonitoring mittels transgener Hefen

Schwermetallionen spielen bei der Reinigung von Abwässern der Galvanik-Industrie eine entscheidende Rolle. Hier muss die Abwasserbehandlung mit Verfahren gekoppelt sein, die diese toxischen Metallionen vom Abwasser trennen. Dazu ist eine kontinuierliche Messung der spezifischen Verbindungen, d.h. der Schwermetallionen-Konzentration, essentielle Voraussetzung, um mit möglichst geringem Materialeinsatz einen optimalen Reinigungseffekt zu erzielen. Für solche Messungen wird derzeit vor allem die Atomadsorptionsspektrometrie eingesetzt, die zwar sehr exakt, aber auch sehr kostenintensiv ist und nur die absoluten und nicht die biologisch verfügbaren Konzentrationen an Schwermetallbelastungen misst. Zunehmend besteht daher die Forderung nach Messsystemen, die durch eine schnelle, kostengünstige und umweltschonende Schadstofferfassung, speziell von Schwermetallionen, charakterisiert ist, bei der der apparative Aufwand möglichst gering sein soll. Diese Forderungen erfüllen Biosensoren, die durch den Einsatz von gentechnisch veränderten Mikroorganismen, speziell Hefen, auch für solche Aufgabenstellungen genutzt werden können

Schizosaccharomyces pombe Ofd2 Is a Nuclear 2-Oxoglutarate and Iron Dependent Dioxygenase Interacting with Histones

2-oxoglutarate (2OG) dependent dioxygenases are ubiquitous iron containing enzymes that couple substrate oxidation to the conversion of 2OG to succinate and carbon dioxide. They participate in a wide range of biological processes including collagen biosynthesis, fatty acid metabolism, hypoxic sensing and demethylation of nucleic acids and histones. Although substantial progress has been made in elucidating their function, the role of many 2OG dioxygenases remains enigmatic. Here we have studied the 2OG and iron (Fe(II)) dependent dioxygenase Ofd2 in Schizosaccharomyces pombe, a member of the AlkB subfamily of dioxygenases. We show that decarboxylation of 2OG by recombinant Ofd2 is dependent on Fe(II) and a histidine residue predicted to be involved in Fe(II) coordination. The decarboxylase activity of Ofd2 is stimulated by histones, and H2A has the strongest effect. Ofd2 interacts with all four core histones, however, only very weakly with H4. Our results define a new subclass of AlkB proteins interacting with histones, which also might comprise some of the human AlkB homologs with unknown function

Breakage Root Cause Analysis in as-Cut Monocrystalline Silicon Wafers

Breakage of silicon wafers during manufacturing is an important issue in the processing of silicon solar cells. By reducing critical loadings with sensitive handling steps and improvement of manufacturing processes, the failure probability of wafers during production was reduced in the last years. Still, it is necessary to find and understand the reasons leading to breakage of silicon wafers. In this work, the subsurface damage is investigated in detail as the main factor for breakage of slurry based multi wire sawn wafers by use of fractographic analysis. The fracture origins, which lead to wafer breakage are identified and interpreted on as-cut monocrystalline wafers in bending tests. Typical origins of breakage are presented which were identified as half-penny shape cracks most likely resulting from indentation processes of SiC grain during wire sawing

Mechanical damage of half-cell cutting technologies in solar cells and module laminates

Half-cell modules are gaining an increasing market share due to their potential of increasing the module power without requiring any changes in the cell technology. However, it has turned out that different cell separation technologies can yield a similar electrical performance of the half-cells, yet leading to an entirely different mechanical behavior of the cells. Hence, the mechanical strength on solar cell and module laminate level was evaluated for thermal laser separation (TLS) and laser scribing with cleaving (LSC) cutting technologies on multicrystalline silicon Al-BSF solar cells. It could be systematically shown, that mechanical defects which are found on cell level can also be seen on module level. More precisely, the strength for the LSC batch was decreased by 35 % on cell level and 23 % on module level. The TLS process did not change significantly the strength on cell or module laminate level. Additionally, the origin of fracture was found at the edge for the laser batch and on the back side pads for the full cells and TLS cut cells. The electrical evaluation has shown minor electrical power losses of the half-cells leading to an efficiency reduction of less than 1 %rel