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排序方式: 共有893条查询结果,搜索用时 18 毫秒
61.
Denschlag J Simsarian JE Feder DL Clark CW Collins LA Cubizolles J Deng L Hagley EW Helmerson K Reinhardt WP Rolston SL Schneider BI Phillips WD 《Science (New York, N.Y.)》2000,287(5450):97-101
Quantum phase engineering is demonstrated with two techniques that allow the spatial phase distribution of a Bose-Einstein condensate (BEC) to be written and read out. A quantum state was designed and produced by optically imprinting a phase pattern onto a BEC of sodium atoms, and matter-wave interferometry with spatially resolved imaging was used to analyze the resultant phase distribution. An appropriate phase imprint created solitons, the first experimental realization of this nonlinear phenomenon in a BEC. The subsequent evolution of these excitations was investigated both experimentally and theoretically. 相似文献
62.
Construction of a general human chromosome jumping library, with application to cystic fibrosis 总被引:22,自引:0,他引:22
F S Collins M L Drumm J L Cole W K Lockwood G F Vande Woude M C Iannuzzi 《Science (New York, N.Y.)》1987,235(4792):1046-1049
In many genetic disorders, the responsible gene and its protein product are unknown. The technique known as "reverse genetics," in which chromosomal map positions and genetically linked DNA markers are used to identify and clone such genes, is complicated by the fact that the molecular distances from the closest DNA markers to the gene itself are often too large to traverse by standard cloning techniques. To address this situation, a general human chromosome jumping library was constructed that allows the cloning of DNA sequences approximately 100 kilobases away from any starting point in genomic DNA. As an illustration of its usefulness, this library was searched for a jumping clone, starting at the met oncogene, which is a marker tightly linked to the cystic fibrosis gene that is located on human chromosome 7. Mapping of the new genomic fragment by pulsed field gel electrophoresis confirmed that it resides on chromosome 7 within 240 kilobases downstream of the met gene. The use of chromosome jumping should now be applicable to any genetic locus for which a closely linked DNA marker is available. 相似文献
63.
Increased insulin sensitivity and obesity resistance in mice lacking the protein tyrosine phosphatase-1B gene 总被引:1,自引:0,他引:1
Elchebly M Payette P Michaliszyn E Cromlish W Collins S Loy AL Normandin D Cheng A Himms-Hagen J Chan CC Ramachandran C Gresser MJ Tremblay ML Kennedy BP 《Science (New York, N.Y.)》1999,283(5407):1544-1548
Protein tyrosine phosphatase-1B (PTP-1B) has been implicated in the negative regulation of insulin signaling. Disruption of the mouse homolog of the gene encoding PTP-1B yielded healthy mice that, in the fed state, had blood glucose concentrations that were slightly lower and concentrations of circulating insulin that were one-half those of their PTP-1B+/+ littermates. The enhanced insulin sensitivity of the PTP-1B-/- mice was also evident in glucose and insulin tolerance tests. The PTP-1B-/- mice showed increased phosphorylation of the insulin receptor in liver and muscle tissue after insulin injection in comparison to PTP-1B+/+ mice. On a high-fat diet, the PTP-1B-/- and PTP-1B+/- mice were resistant to weight gain and remained insulin sensitive, whereas the PTP-1B+/+ mice rapidly gained weight and became insulin resistant. These results demonstrate that PTP-1B has a major role in modulating both insulin sensitivity and fuel metabolism, thereby establishing it as a potential therapeutic target in the treatment of type 2 diabetes and obesity. 相似文献
64.
Sutton T Baumann U Hayes J Collins NC Shi BJ Schnurbusch T Hay A Mayo G Pallotta M Tester M Langridge P 《Science (New York, N.Y.)》2007,318(5855):1446-1449
65.
Ellipsosomes: organelles containing a cytochrome-like pigment in the retinal cones of certain fishes 总被引:1,自引:0,他引:1
E F MacNichol Y W Kunz J S Levine F I Hárosi B A Collins 《Science (New York, N.Y.)》1978,200(4341):549-552
Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters. 相似文献
66.
Ranson H Claudianos C Ortelli F Abgrall C Hemingway J Sharakhova MV Unger MF Collins FH Feyereisen R 《Science (New York, N.Y.)》2002,298(5591):179-181
The emergence of insecticide resistance in the mosquito poses a serious threat to the efficacy of many malaria control programs. We have searched the Anopheles gambiae genome for members of the three major enzyme families- the carboxylesterases, glutathione transferases, and cytochrome P450s-that are primarily responsible for metabolic resistance to insecticides. A comparative genomic analysis with Drosophila melanogaster reveals that a considerable expansion of these supergene families has occurred in the mosquito. Low gene orthology and little chromosomal synteny paradoxically contrast the easily identified orthologous groups of genes presumably seeded by common ancestors. In A. gambiae, the independent expansion of paralogous genes is mainly a consequence of the formation of clusters among locally duplicated genes. These expansions may reflect the functional diversification of supergene families consistent with major differences in the life history and ecology of these organisms. These data provide a basis for identifying the resistance-associated enzymes within these families. This will enable the resistance status of mosquitoes, flies, and possibly other holometabolous insects to be monitored. The analyses also provide the means for identifying previously unknown molecules involved in fundamental biological processes such as development. 相似文献
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