Versuche zur Synthese von Verbindungen der Steroidreihe

Summary Reduction of the ketal II of 7-keto-1,4-dimethoxy-4b-methyl-5, 6, 7, 9, 10-hexahydrophenanthrene with lithium in liquid ammonia furnishes a corresponding dihydro derivative, from which a tricyclic triketone, m.p. 121°, is obtained upon acid hydrolysis. This triketone is identical with the recently described antitrans-4b-methyl-1, 2, 3, 4, 4a, 4b, 5, 6, 7, 9, 10, 10-dodecahydro-phenanthrene-1, 4, 7-trione III and thus conforms to the stereochemistry of the natural steroids.     

Congressus

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Corrigenda

     

Phosphate concentrations in lakes

Phosphate is an important nutrient that restricts microbial production in many freshwater and marine environments. The actual concentration of phosphate in phosphorus-limited waters is largely unknown because commonly used chemical and radiochemical techniques overestimate the concentration. Here, using a new steady-state radiobioassay to survey a diverse set of lakes, we report phosphate concentrations in lakes that are orders of magnitude lower than estimates made spectrophotometrically or with the frequently used Rigler radiobioassay. Our results, combined with those from the literature, indicate that microbes can achieve rapid turnover rates at picomolar nutrient concentrations. This occurs even though these concentrations are about two orders of magnitude below the level where phosphate uptake is estimated to be half the saturation level for the pico-plankton community. Also, while phosphate concentration increased with the concentration of total phosphorus and soluble reactive phosphorus in the lakes we sampled, the proportion of phosphate in the total phosphorus pool decreased from oligotrophic to eutrophic lakes. Such information, as revealed by the phosphate assay that we use here, should allow us to address hypotheses concerning the concentration of phosphate available to planktonic microorganisms in aquatic systems.     

Purification of 2-deoxy-2-dansylamido-D-glucose by affinity chromatography on a lectin-loaded agarose column.

A method is demonstrated to purify 2-substituted derivatives of glucose and sterically related sugars by affinity chromatography on Con A-sepharose. The method seems to be of rather general applicability.     

SLX4, a coordinator of structure-specific endonucleases, is mutated in a new Fanconi anemia subtype

DNA interstrand crosslink repair requires several classes of proteins, including structure-specific endonucleases and Fanconi anemia proteins. SLX4, which coordinates three separate endonucleases, was recently recognized as an important regulator of DNA repair. Here we report the first human individuals found to have biallelic mutations in SLX4. These individuals, who were previously diagnosed as having Fanconi anemia, add SLX4 as an essential component to the FA-BRCA genome maintenance pathway.     

At the crossroads from Asia to Europe: spring migration of raptors and black storks in Dadia National Park (Greece)

Migrating raptors and black storks (Ciconia nigra) were studied in Dadia National Park, Greece, during spring 2003–2005. Vantage points and transects were used to evaluate magnitude, phenology, local variation and direction. We observed 23 species and 2030 individuals, including 715 common buzzards (Buteo buteo), 547 black storks and 136 short-toed eagles (Circaetus gallicus). Species-specific migration peaks were detected, starting in the second half of March, e.g. common buzzard, short-toed eagle, black stork, and ending early May, e.g. Levant sparrowhawk (Accipiter brevipes), red-footed falcon (Falco vespertinus), honey buzzard (Pernis apivorus). Most raptors were observed in the Evros valley, which may function as a migration corridor. The average direction of passing raptors was north. Species’ proportions and phenology in the study area were similar to those in neighbouring Bosphorus and Marmara Flyways. Further migration monitoring should be established in the area, which will provide important information not least to inform wind farm development location.     

Multi-Disciplinary North-South Collaboration in Participatory Action Research on Food Value Chains: a German-Tanzanian Case Study on Perceptions,Experiences and Challenges

Systemic Practice and Action Research - Upgrading local food value chains is a promising approach to invigorating African food systems. This endeavour warrants multi-disciplinary North-South...