Free University of Berlin

About: Free University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Population & Context (language use). The organization has 35195 authors who have published 66525 publications receiving 2094403 citations. The organization is also known as: FU Berlin.

Three-dimensional structure of system I of photosynthesis at 6 Å resolution

Abstract: X-ray structure analysis shows that the monomer of trimeric photosystem I (PS I) of Synechococcus sp. consists of a catalytic domain and a smaller domain that connects the monomers. The 4Fe–4S clusters FX,FA and FB, 28 α-helices and 45 chlorophyll a molecules were located. The two large subunits of PS I are represented by nine a-helices each; they are related by a local 2-fold rotation axis passing through Fx. Electron densities close to this axis are interpreted as carriers of the electron transfer chain.

Sensitizing soluble guanylyl cyclase to become a highly CO-sensitive enzyme.

Abstract: It took at least a decade to realize that the toxic gas NO is the physiological activator of soluble guanylyl cyclase (sGC), thereby acting as a signaling molecule in the nervous and cardiovascular systems. Despite its rather poor sGC-activating property, CO has also been implicated as a physiological stimulator of sGC in neurotransmission and vasorelaxation. Here, we establish YC-1 as a novel NO-independent sGC activator that potentiates both CO- and NO-induced sGC stimulation. As this potentiating effect is also observed with protoporphyrin IX which activates sGC independently of a gaseous ligand, we conclude that stabilization of the enzyme's active configuration is the underlying mechanism of YC-1's action. Moreover, the results obtained with YC-1 reveal that CO is capable of stimulating sGC to a degree similar to NO, and thus provide the molecular basis for CO functioning as a signaling molecule.

The zero-inflated Poisson model and the decayed, missing and filled teeth index in dental epidemiology

Abstract: For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.

Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover

Abstract: The second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth down to 2 m. This subsurface sampling capability will provide the best chance yet to gain access to chemical biosignatures. Using the powerful Pasteur payload instruments, the ExoMars science team will conduct a holistic search for traces of life and seek corroborating geological context information. Key Words: Biosignatures-ExoMars-Landing sites-Mars rover-Search for life. Astrobiology 17, 471-510.