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排序方式: 共有452条查询结果,搜索用时 15 毫秒
31.
Kurth WS Gurnett DA Hospodarsky GB Farrell WM Roux A Dougherty MK Joy SP Kivelson MG Walker RJ Crary FJ Alexander CJ 《Nature》2002,415(6875):991-994
Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snapshot of a transient event in progress. Here we present a set of nearly simultaneous two-point measurements of the jovian magnetopause at a time when the jovian magnetopause was in a state of transition from a relatively larger to a relatively smaller size in response to an increase in solar-wind pressure. The response of Jupiter's magnetopause is very similar to that of the Earth, confirming that the understanding built on studies of the Earth's magnetosphere is valid. The data also reveal evidence for a well-developed boundary layer just inside the magnetopause. 相似文献
32.
Grimm DR Colter MB Braunschweig M Alexander LJ Neame PJ Kim HK 《Cellular and molecular life sciences : CMLS》2001,58(1):148-159
Factor V is a plasma protein essential for blood coagulation. This protein is involved in activated protein C resistance,
the most common inherited thrombotic disorder known. We utilized the polymerase chain reaction to clone the porcine factor
V gene by generating overlapping clones amplified with primers chosen by comparison with known nucleotide sequences. The porcine
factor V cDNA contig encodes a predicted 2258-amino acid protein, making it the largest in comparison to the bovine, human,
and murine proteins. Porcine factor V has the highest level of homology with bovine factor V, but also has high levels of
conservation of important residues with all the species. Radiation hybrid mapping assigned the porcine factor V gene to chromosome
4. Three-dimensional models of factor V were generated and used to analyze membrane-binding sites in terms of conserved, and
therefore likely important residues.
Received 3 October 2000; revised 23 November 2000; accepted 6 December 2000 相似文献
33.
Genzel R Schödel R Ott T Eckart A Alexander T Lacombe F Rouan D Aschenbach B 《Nature》2003,425(6961):934-937
Recent measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* (refs 4, 5) at the Galactic Centre is a 3.6-million-solar-mass black hole. Sgr A* is remarkably faint in all wavebands other than the radio region, however, which challenges current theories of matter accretion and radiation surrounding black holes. The black hole's rotation rate is not known, and therefore neither is the structure of space-time around it. Here we report high-resolution infrared observations of Sgr A* that reveal 'quiescent' emission and several flares. The infrared emission originates from within a few milliarcseconds of the black hole, and traces very energetic electrons or moderately hot gas within the innermost accretion region. Two flares exhibit a 17-minute quasi-periodic variability. If the periodicity arises from relativistic modulation of orbiting gas, the emission must come from just outside the event horizon, and the black hole must be rotating at about half of the maximum possible rate. 相似文献
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Kamath RS Fraser AG Dong Y Poulin G Durbin R Gotta M Kanapin A Le Bot N Moreno S Sohrmann M Welchman DP Zipperlen P Ahringer J 《Nature》2003,421(6920):231-237
38.
Singh N Ebrahimi FA Gimelbrant AA Ensminger AW Tackett MR Qi P Gribnau J Chess A 《Nature genetics》2003,33(3):339-341
Random monoallelic expression and asynchronous replication define an unusual class of autosomal mammalian genes. We show that every cell has randomly chosen either the maternal or paternal copy of each given autosome pair, such that alleles of these genes scattered across the chosen chromosome replicate earlier than the alleles on the homologous chromosome. Thus, chromosome-pair non-equivalence, rather than being limited to X-chromosome inactivation, is a fundamental property of mouse chromosomes. 相似文献
39.
Three-dimensional structural dynamics of myosin V by single-molecule fluorescence polarization 总被引:14,自引:0,他引:14
The structural change that generates force and motion in actomyosin motility has been proposed to be tilting of the myosin light chain domain, which serves as a lever arm. Several experimental approaches have provided support for the lever arm hypothesis; however, the extent and timing of tilting motions are not well defined in the motor protein complex of functioning actomyosin. Here we report three-dimensional measurements of the structural dynamics of the light chain domain of brain myosin V using a single-molecule fluorescence polarization technique that determines the orientation of individual protein domains with 20-40-ms time resolution. Single fluorescent calmodulin light chains tilted back and forth between two well-defined angles as the myosin molecule processively translocated along actin. The results provide evidence for lever arm rotation of the calmodulin-binding domain in myosin V, and support a 'hand-over-hand' mechanism for the translocation of double-headed myosin V molecules along actin filaments. The technique is applicable to the study of real-time structural changes in other biological systems. 相似文献
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