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Protein intrinsic disorder is becoming increasingly recognized in proteomics research. While lacking structure, many regions of disorder have been associated with biological function. There are many different experimental methods for characterizing intrinsically disordered proteins and regions; nevertheless, the prediction of intrinsic disorder from amino acid sequence remains a useful strategy especially for many large-scale proteomic investigations. Here we introduced a consensus artificial neural network (ANN) prediction method, which was developed by combining the outputs of several individual disorder predictors. By eight-fold cross-validation, this meta-predictor, called PONDR-FIT, was found to improve the prediction accuracy over a range of 3 to 20% with an average of 11% compared to the single predictors, depending on the datasets being used. Analysis of the errors shows that the worst accuracy still occurs for short disordered regions with less than ten residues, as well as for the residues close to order/disorder boundaries. Increased understanding of the underlying mechanism by which such meta-predictors give improved predictions will likely promote the further development of protein disorder predictors. Access to PONDR-FIT is available at www.disprot.org.  相似文献   
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The fd filamentous phage can be contracted to short rods called I-forms and to spheroidal particles called S-forms. The conversions from fd----I-forms----S-forms were previously suggested to mimic steps in fd penetration. The same conversions, in reverse order, were suggested to mimic steps in fd assembly. The I-forms and S-forms bind the hydrophobic probe, 1-anilino-napthalene-8-sulfonate (ANS); under the same conditions, fd binds this probe very poorly. Rigidly packed side chains in fd and nonrigidly packed side chains in I-forms and S-forms would explain the differences in ANS binding. A compilation of the properties of I-forms and S-forms indicate that: (i) they have compact structures; (ii) they have secondary structures of the same type as native phage; (iii) they have non-native morphologies; and (iv) they may have nonrigid side chain packing. These are the properties of molten globules.  相似文献   
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Arenaviruses are one of the largest families of human hemorrhagic fever viruses and are known to infect both mammals and snakes. Arenaviruses package a large (L) and small (S) genome segment in their virions. For segmented RNA viruses like these, novel genotypes can be generated through mutation, recombination, and reassortment. Although it is believed that an ancient recombination event led to the emergence of a new lineage of mammalian arenaviruses, neither recombination nor reassortment has been definitively documented in natural arenavirus infections. Here, we used metagenomic sequencing to survey the viral diversity present in captive arenavirus-infected snakes. From 48 infected animals, we determined the complete or near complete sequence of 210 genome segments that grouped into 23 L and 11 S genotypes. The majority of snakes were multiply infected, with up to 4 distinct S and 11 distinct L segment genotypes in individual animals. This S/L imbalance was typical: in all cases intrahost L segment genotypes outnumbered S genotypes, and a particular S segment genotype dominated in individual animals and at a population level. We corroborated sequencing results by qRT-PCR and virus isolation, and isolates replicated as ensembles in culture. Numerous instances of recombination and reassortment were detected, including recombinant segments with unusual organizations featuring 2 intergenic regions and superfluous content, which were capable of stable replication and transmission despite their atypical structures. Overall, this represents intrahost diversity of an extent and form that goes well beyond what has been observed for arenaviruses or for viruses in general. This diversity can be plausibly attributed to the captive intermingling of sub-clinically infected wild-caught snakes. Thus, beyond providing a unique opportunity to study arenavirus evolution and adaptation, these findings allow the investigation of unintended anthropogenic impacts on viral ecology, diversity, and disease potential.  相似文献   
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姬强  孙汉印  Taraqqi AK  王旭东   《生态学杂志》2014,25(4):1029-1035
在连续8年田间定位试验的基础上,分析了关中平原冬小麦 夏玉米复种连作系统2008—2009年连续两个生长季期间不同耕作措施(结合秸秆还田和不还田)对土壤有机碳和水分利用率的影响.结果表明: 相对于传统耕作,保护性耕作有利于土壤有机碳、水分利用效率和作物产量的提高,其中在“深松+秸秆还田”耕作模式下的增幅最高,土壤有机碳含量在0~30 cm土层增幅达到19.5%,水分利用效率和作物产量提高了16.9%和20.5%,而免耕模式则有效提高了0~10 cm土层有机碳含量.在该地区土壤和气候条件下,深松结合秸秆粉碎还田是最理想的耕作模式,最有利于土壤有机碳累积,并提高水分利用效率和作物产量.  相似文献   
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Intrinsically disordered proteins and intrinsically disordered protein regions are highly abundant in nature. However, the quantitative and qualitative measures of protein intrinsic disorder in species with known genomes are still not available. Furthermore, although the correlation between high fraction of disordered residues and advanced species has been reported, the details of this correlation and the connection between the disorder content and proteome complexity have not been reported as of yet. To fill this gap, we analysed entire proteomes of 3484 species from three domains of life (archaea, bacteria and eukaryotes) and from viruses. Our analysis revealed that the evolution process is characterized by distinctive patterns of changes in the protein intrinsic disorder content. We are showing here that viruses are characterized by the widest spread of the proteome disorder content (the percentage of disordered residues ranges from 7.3% in human coronavirus NL63 to 77.3% in Avian carcinoma virus). For several organisms, a clear correlation is seen between their disorder contents and habitats. In multicellular eukaryotes, there is a weak correlation between the complexity of an organism (evaluated as a number of different cell types) and its overall disorder content. For both the prokaryotes and eukaryotes, the disorder content is generally independent of the proteome size. However, disorder shows a sharp increase associated with the transition from prokaryotic to eukaryotic cells. This suggests that the increased disorder content in eukaryotic proteomes might be used by nature to deal with the increased cell complexity due to the appearance of the various cellular compartments.  相似文献   
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The stereochemical constraints originally used to construct two- and three-stranded alpha-helical coiled-coils were generalized for aggregates of alpha-helices containing from 4 to 14 alpha-helices in tubular bundles. Certain features of bacteriorhodopsin show excellent correlations with these stereochemical constraints.  相似文献   
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