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排序方式: 共有1074条查询结果,搜索用时 31 毫秒
61.
Rensing SA Lang D Zimmer AD Terry A Salamov A Shapiro H Nishiyama T Perroud PF Lindquist EA Kamisugi Y Tanahashi T Sakakibara K Fujita T Oishi K Shin-I T Kuroki Y Toyoda A Suzuki Y Hashimoto S Yamaguchi K Sugano S Kohara Y Fujiyama A Anterola A Aoki S Ashton N Barbazuk WB Barker E Bennetzen JL Blankenship R Cho SH Dutcher SK Estelle M Fawcett JA Gundlach H Hanada K Heyl A Hicks KA Hughes J Lohr M Mayer K Melkozernov A Murata T Nelson DR Pils B Prigge M Reiss B Renner T Rombauts S Rushton PJ 《Science (New York, N.Y.)》2008,319(5859):64-69
We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics. 相似文献
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Discovery and directed evolution of a glyphosate tolerance gene 总被引:2,自引:0,他引:2
Castle LA Siehl DL Gorton R Patten PA Chen YH Bertain S Cho HJ Duck N Wong J Liu D Lassner MW 《Science (New York, N.Y.)》2004,304(5674):1151-1154
The herbicide glyphosate is effectively detoxified by N-acetylation. We screened a collection of microbial isolates and discovered enzymes exhibiting glyphosate N-acetyltransferase (GAT) activity. Kinetic properties of the discovered enzymes were insufficient to confer glyphosate tolerance to transgenic organisms. Eleven iterations of DNA shuffling improved enzyme efficiency by nearly four orders of magnitude from 0.87 mM-1 min-1 to 8320 mM-1 min-1. From the fifth iteration and beyond, GAT enzymes conferred increasing glyphosate tolerance to Escherichia coli, Arabidopsis, tobacco, and maize. Glyphosate acetylation provides an alternative strategy for supporting glyphosate use on crops. 相似文献
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Cho A 《Science (New York, N.Y.)》2008,321(5894):1287-1289
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Schubert EF Hunt NE Micovic M Malik RJ Sivco DL Cho AY Zydzik GJ 《Science (New York, N.Y.)》1994,265(5174):943-945
One-dimensional microcavities are optical resonators with coplanar reflectors separated by a distance on the order of the optical wavelength. Such structures quantize the energy of photons propagating along the optical axis of the cavity and thereby strongly modify the spontaneous emission properties of a photon-emitting medium inside a microcavity. This report concerns semiconductor light-emitting diodes with the photon-emitting active region of the light-emitting diodes placed inside a microcavity. These devices are shown to have strongly modified emission properties including experimental emission efficiencies that are higher by more than a factor of 5 and theoretical emission efficiencies that are higher by more than a factor of 10 than the emission efficiencies in conventional light-emitting diodes. 相似文献
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We have determined the 2.6 angstrom crystal structure of the entire extracellular region of human HER3 (ErbB3), a member of the epidermal growth factor receptor (EGFR) family. The structure consists of four domains with structural homology to domains found in the type I insulin-like growth factor receptor. The HER3 structure reveals a contact between domains II and IV that constrains the relative orientations of ligand-binding domains and provides a structural basis for understanding both multiple-affinity forms of EGFRs and conformational changes induced in the receptor by ligand binding during signaling. These results also suggest new therapeutic approaches to modulating the behavior of members of the EGFR family. 相似文献
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Previous measurements of the hydroxyl (OH-) ion content of the calcium phosphate crystals of bone mineral have indicated a substantial depletion or near-absence of OH-, despite its presumed status as a constituent of the hydroxyapatite lattice. Analytical methods for determining bone crystal OH- content have depended on procedures or assumptions that may have biased the results, such as chemical pretreatment to eliminate interference from the organic matrix. We demonstrate a two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy technique that detects the proton spectrum of bone crystals while suppressing the interfering matrix signals, eliminating the need for specimen pretreatment other than cryogenic grinding. Results on fresh-frozen and ground whole bone of several mammalian species show that the bone crystal OH- is readily detectable; a rough estimate yields an OH- content of human cortical bone of about 20% of the amount expected in stoichiometric hydroxyapatite. This finding sheds light on the biochemical processes underlying normal and abnormal bone mineral metabolism. 相似文献