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Ecosystems - Humid tropical forests on highly weathered soils are often characterized by low bioavailable phosphorus (P) concentrations. These ecosystems also often experience low and fluctuating... 相似文献
73.
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%–70% of all worm proteins observed to have more than seven protein–protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long unstructured loops are a major part of unstructured regions in molecular networks. 相似文献
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75.
The integration of X-inactivation with development is a crucial aspect of this classical paradigm of epigenetic regulation. During early female mouse development, X-inactivation reprogramming occurs in pluripotent cells of the inner cell mass of the blastocyst and in pluripotent primordial germ cells. Here we discuss the developmental strategies which ensure the coupling of the regulation of X-inactivation to the acquisition of pluripotency through the regulation of the master of X-inactivation, the non-coding Xist gene, by the key factors which support pluripotency Nanog, Oct4 and Sox2. 相似文献
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In this paper, we introduce a model of malaria, a disease that involves a complex life cycle of parasites, requiring both human and mosquito hosts. The novelty of the model is the introduction of periodic coefficients into the system of one-dimensional equations, which account for the seasonal variations (wet and dry seasons) in the mosquito birth and death rates. We define a basic reproduction number R(0) that depends on the periodic coefficients and prove that if R(0)<1 then the disease becomes extinct, whereas if R(0)>1 then the disease is endemic and may even be periodic. 相似文献
78.
This paper proposes a physical model involving the key structures within the neural cytoskeleton as major players in molecular-level
processing of information required for learning and memory storage. In particular, actin filaments and microtubules are macromolecules
having highly charged surfaces that enable them to conduct electric signals. The biophysical properties of these filaments
relevant to the conduction of ionic current include a condensation of counterions on the filament surface and a nonlinear
complex physical structure conducive to the generation of modulated waves. Cytoskeletal filaments are often directly connected
with both ionotropic and metabotropic types of membrane-embedded receptors, thereby linking synaptic inputs to intracellular
functions. Possible roles for cable-like, conductive filaments in neurons include intracellular information processing, regulating
developmental plasticity, and mediating transport. The cytoskeletal proteins form a complex network capable of emergent information
processing, and they stand to intervene between inputs to and outputs from neurons. In this manner, the cytoskeletal matrix
is proposed to work with neuronal membrane and its intrinsic components (e.g., ion channels, scaffolding proteins, and adaptor
proteins), especially at sites of synaptic contacts and spines. An information processing model based on cytoskeletal networks
is proposed that may underlie certain types of learning and memory. 相似文献
79.
David Goudenège Stéphane Avner Céline Lucchetti-Miganeh Frédérique Barloy-Hubler 《BMC microbiology》2010,10(1):88
Background
The functions of proteins are strongly related to their localization in cell compartments (for example the cytoplasm or membranes) but the experimental determination of the sub-cellular localization of proteomes is laborious and expensive. A fast and low-cost alternative approach is in silico prediction, based on features of the protein primary sequences. However, biologists are confronted with a very large number of computational tools that use different methods that address various localization features with diverse specificities and sensitivities. As a result, exploiting these computer resources to predict protein localization accurately involves querying all tools and comparing every prediction output; this is a painstaking task. Therefore, we developed a comprehensive database, called CoBaltDB, that gathers all prediction outputs concerning complete prokaryotic proteomes. 相似文献80.