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81.
Plectasin is a peptide antibiotic with therapeutic potential from a saprophytic fungus 总被引:4,自引:0,他引:4
Mygind PH Fischer RL Schnorr KM Hansen MT Sönksen CP Ludvigsen S Raventós D Buskov S Christensen B De Maria L Taboureau O Yaver D Elvig-Jørgensen SG Sørensen MV Christensen BE Kjaerulff S Frimodt-Moller N Lehrer RI Zasloff M Kristensen HH 《Nature》2005,437(7061):975-980
Animals and higher plants express endogenous peptide antibiotics called defensins. These small cysteine-rich peptides are active against bacteria, fungi and viruses. Here we describe plectasin-the first defensin to be isolated from a fungus, the saprophytic ascomycete Pseudoplectania nigrella. Plectasin has primary, secondary and tertiary structures that closely resemble those of defensins found in spiders, scorpions, dragonflies and mussels. Recombinant plectasin was produced at a very high, and commercially viable, yield and purity. In vitro, the recombinant peptide was especially active against Streptococcus pneumoniae, including strains resistant to conventional antibiotics. Plectasin showed extremely low toxicity in mice, and cured them of experimental peritonitis and pneumonia caused by S. pneumoniae as efficaciously as vancomycin and penicillin. These findings identify fungi as a novel source of antimicrobial defensins, and show the therapeutic potential of plectasin. They also suggest that the defensins of insects, molluscs and fungi arose from a common ancestral gene. 相似文献
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Berger E Price PA Cenko SB Gal-Yam A Soderberg AM Kasliwal M Leonard DC Cameron PB Frail DA Kulkarni SR Murphy DC Krzeminski W Piran T Lee BL Roth KC Moon DS Fox DB Harrison FA Persson SE Schmidt BP Penprase BE Rich J Peterson BA Cowie LL 《Nature》2005,438(7070):988-990
Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness--the long-soft and the short-hard bursts. The discovery of afterglow emission from long GRBs was a watershed event, pinpointing their origin to star-forming galaxies, and hence the death of massive stars, and indicating an energy release of about 10(51) erg. While theoretical arguments suggest that short GRBs are produced in the coalescence of binary compact objects (neutron stars or black holes), the progenitors, energetics and environments of these events remain elusive despite recent localizations. Here we report the discovery of the first radio afterglow from the short burst GRB 050724, which unambiguously associates it with an elliptical galaxy at a redshift z = 0.257. We show that the burst is powered by the same relativistic fireball mechanism as long GRBs, with the ejecta possibly collimated in jets, but that the total energy release is 10-1,000 times smaller. More importantly, the nature of the host galaxy demonstrates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors. 相似文献
83.
The light/dark cycle of day and night synchronizes an internal 'biological clock' that governs daily rhythms in behaviour, but this form of regulation is denied to polar animals for most of the year. Here we demonstrate that the continuous lighting conditions of summer and of winter at high latitudes cause a loss in daily rhythmic activity in reindeer living far above the Arctic Circle. This seasonal absence of circadian rhythmicity may be a ubiquitous trait among resident polar vertebrates. 相似文献
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Araki T Enomoto S Furuno K Gando Y Ichimura K Ikeda H Inoue K Kishimoto Y Koga M Koseki Y Maeda T Mitsui T Motoki M Nakajima K Ogawa H Ogawa M Owada K Ricol JS Shimizu I Shirai J Suekane F Suzuki A Tada K Takeuchi S Tamae K Tsuda Y Watanabe H Busenitz J Classen T Djurcic Z Keefer G Leonard D Piepke A Yakushev E Berger BE Chan YD Decowski MP Dwyer DA Freedman SJ Fujikawa BK Goldman J Gray F Heeger KM Hsu L Lesko KT Luk KB Murayama H O'Donnell T Poon AW Steiner HM Winslow LA Mauger C McKeown RD 《Nature》2005,436(7050):499-503
The detection of electron antineutrinos produced by natural radioactivity in the Earth could yield important geophysical information. The Kamioka liquid scintillator antineutrino detector (KamLAND) has the sensitivity to detect electron antineutrinos produced by the decay of 238U and 232Th within the Earth. Earth composition models suggest that the radiogenic power from these isotope decays is 16 TW, approximately half of the total measured heat dissipation rate from the Earth. Here we present results from a search for geoneutrinos with KamLAND. Assuming a Th/U mass concentration ratio of 3.9, the 90 per cent confidence interval for the total number of geoneutrinos detected is 4.5 to 54.2. This result is consistent with the central value of 19 predicted by geophysical models. Although our present data have limited statistical power, they nevertheless provide by direct means an upper limit (60 TW) for the radiogenic power of U and Th in the Earth, a quantity that is currently poorly constrained. 相似文献
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Most species live in species-rich food webs; yet, for a century, most mathematical models for population dynamics have included only one or two species. We ask whether such models are relevant to the real world. Two-species population models of an interacting consumer and resource collapse to one-species dynamics when recruitment to the resource population is unrelated to resource abundance, thereby weakening the coupling between consumer and resource. We predict that, in nature, generalist consumers that feed on many species should similarly show one-species dynamics. We test this prediction using cyclic populations, in which it is easier to infer underlying mechanisms, and which are widespread in nature. Here we show that one-species cycles can be distinguished from consumer resource cycles by their periods. We then analyse a large number of time series from cyclic populations in nature and show that almost all cycling, generalist consumers examined have periods that are consistent with one-species dynamics. Thus generalist consumers indeed behave as if they were one-species populations, and a one-species model is a valid representation for generalist population dynamics in many-species food webs. 相似文献
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Mikkelsen TS Hanna J Zhang X Ku M Wernig M Schorderet P Bernstein BE Jaenisch R Lander ES Meissner A 《Nature》2008,454(7200):49-55
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Meissner A Mikkelsen TS Gu H Wernig M Hanna J Sivachenko A Zhang X Bernstein BE Nusbaum C Jaffe DB Gnirke A Jaenisch R Lander ES 《Nature》2008,454(7205):766-770
DNA methylation is essential for normal development and has been implicated in many pathologies including cancer. Our knowledge about the genome-wide distribution of DNA methylation, how it changes during cellular differentiation and how it relates to histone methylation and other chromatin modifications in mammals remains limited. Here we report the generation and analysis of genome-scale DNA methylation profiles at nucleotide resolution in mammalian cells. Using high-throughput reduced representation bisulphite sequencing and single-molecule-based sequencing, we generated DNA methylation maps covering most CpG islands, and a representative sampling of conserved non-coding elements, transposons and other genomic features, for mouse embryonic stem cells, embryonic-stem-cell-derived and primary neural cells, and eight other primary tissues. Several key findings emerge from the data. First, DNA methylation patterns are better correlated with histone methylation patterns than with the underlying genome sequence context. Second, methylation of CpGs are dynamic epigenetic marks that undergo extensive changes during cellular differentiation, particularly in regulatory regions outside of core promoters. Third, analysis of embryonic-stem-cell-derived and primary cells reveals that 'weak' CpG islands associated with a specific set of developmentally regulated genes undergo aberrant hypermethylation during extended proliferation in vitro, in a pattern reminiscent of that reported in some primary tumours. More generally, the results establish reduced representation bisulphite sequencing as a powerful technology for epigenetic profiling of cell populations relevant to developmental biology, cancer and regenerative medicine. 相似文献