Detection and imaging of atmospheric radio flashes from cosmic ray air showers

The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.     

Solution structure of a protein denatured state and folding intermediate

The most controversial area in protein folding concerns its earliest stages. Questions such as whether there are genuine folding intermediates, and whether the events at the earliest stages are just rearrangements of the denatured state or progress from populated transition states, remain unresolved. The problem is that there is a lack of experimental high-resolution structural information about early folding intermediates and denatured states under conditions that favour folding because competent states spontaneously fold rapidly. Here we have solved directly the solution structure of a true denatured state by nuclear magnetic resonance under conditions that would normally favour folding, and directly studied its equilibrium and kinetic behaviour. We engineered a mutant of Drosophila melanogaster Engrailed homeodomain that folds and unfolds reversibly just by changing ionic strength. At high ionic strength, the mutant L16A is an ultra-fast folding native protein, just like the wild-type protein; however, at physiological ionic strength it is denatured. The denatured state is a well-ordered folding intermediate, poised to fold by docking helices and breaking some non-native interactions. It unfolds relatively progressively with increasingly denaturing conditions, and so superficially resembles a denatured state with properties that vary with conditions. Such ill-defined unfolding is a common feature of early folding intermediate states and accounts for why there are so many controversies about intermediates versus compact denatured states in protein folding.     

Calcium triggers exit from meiosis II by targeting the APC/C inhibitor XErp1 for degradation

Vertebrate eggs awaiting fertilization are arrested at metaphase of meiosis II by a biochemical activity termed cytostatic factor (CSF). This activity inhibits the anaphase-promoting complex/cyclosome (APC/C), a ubiquitin ligase that triggers anaphase onset and mitotic/meiotic exit by targeting securin and M-phase cyclins for destruction. On fertilization a transient rise in free intracellular calcium causes release from CSF arrest and thus APC/C activation. Although it has previously been shown that calcium induces the release of APC/C from CSF inhibition through calmodulin-dependent protein kinase II (CaMKII), the relevant substrates of this kinase have not been identified. Recently, we characterized XErp1 (Emi2), an inhibitor of the APC/C and key component of CSF activity in Xenopus egg extract. Here we show that calcium-activated CaMKII triggers exit from meiosis II by sensitizing the APC/C inhibitor XErp1 for polo-like kinase 1 (Plx1)-dependent degradation. Phosphorylation of XErp1 by CaMKII leads to the recruitment of Plx1 that in turn triggers the destruction of XErp1 by phosphorylating a site known to serve as a phosphorylation-dependent degradation signal. These results provide a molecular explanation for how the fertilization-induced calcium increase triggers exit from meiosis II.     

Structure elecidation of mammalian TCDD-metabolites

Summary Thin layer and gas chromatographic examination of the bile of dogs which were given tritium-labelled TCDD revealed the presence of several polar biotransformation products. The structure of 5 phenolic metabolites was elecidated by combined gas chromatography-mass spectrometry. A metabolic breakdown scheme for TCDD in the dog is proposed.     

Chromosomenaberrationen in Tumorasziteszellen des Ehrlich-Karzinoms der Maus nach Röntgenbestrahlungin vivo bei verschiedenen Sauerstoffpartialdrucken

Summary The frequency of radio-induced fragments of chromosomes increases in ascites-cells of the Ehrlich-carcinoma at higher oxygen partial pressure, to which test animals are exposed during irradiation.     

Monoamine pathways to the cerebellum and cerebral cortex

Zusammenfassung In kombinierter histochemischer und biochemischer Untersuchung werden Dopamin-, Noradrenalin-und 5-Hydroxytryptamin-Neurone nach Entfernung von Cortex cerebri und Cerebellum studiert. Es ergibt sich, dass die Noradrenalin-Nerventerminale, welche Cortex cerebri und Cerebellum innervieren, vermutlich von feinen Axonen her stammen, deren Zellkörper mindestens zum Teil in der Formatio reticularis der Medulla oblongata gelegen sind. Die Noradrenalin-und 5-Hydroxytryptamin-Axone, die nach dem Cortex cerebri ziehen, passieren vermutlich zur Hauptsache das Cingulum.     

Induction of anti-Treponema pallidum antibodies in normal rabbits by RNA-immuno-carrier extracted from serum of syphilitic rabbits

Zusammenfassung Es wird bestätigt, dass die i.v. Injektion von RNA aus dem Serum Syphilis-infizierter Kaninchen in gesunde Kaninchen die Bildung der Abwehrstoffe gegenT. pallidum verursacht.