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排序方式: 共有322条查询结果,搜索用时 15 毫秒
71.
An SNP map of human chromosome 22 总被引:35,自引:0,他引:35
Mullikin JC Hunt SE Cole CG Mortimore BJ Rice CM Burton J Matthews LH Pavitt R Plumb RW Sims SK Ainscough RM Attwood J Bailey JM Barlow K Bruskiewich RM Butcher PN Carter NP Chen Y Clee CM Coggill PC Davies J Davies RM Dawson E Francis MD Joy AA Lamble RG Langford CF Macarthy J Mall V Moreland A Overton-Larty EK Ross MT Smith LC Steward CA Sulston JE Tinsley EJ Turney KJ Willey DL Wilson GD McMurray AA Dunham I Rogers J Bentley DR 《Nature》2000,407(6803):516-520
The human genome sequence will provide a reference for measuring DNA sequence variation in human populations. Sequence variants are responsible for the genetic component of individuality, including complex characteristics such as disease susceptibility and drug response. Most sequence variants are single nucleotide polymorphisms (SNPs), where two alternate bases occur at one position. Comparison of any two genomes reveals around 1 SNP per kilobase. A sufficiently dense map of SNPs would allow the detection of sequence variants responsible for particular characteristics on the basis that they are associated with a specific SNP allele. Here we have evaluated large-scale sequencing approaches to obtaining SNPs, and have constructed a map of 2,730 SNPs on human chromosome 22. Most of the SNPs are within 25 kilobases of a transcribed exon, and are valuable for association studies. We have scaled up the process, detecting over 65,000 SNPs in the genome as part of The SNP Consortium programme, which is on target to build a map of 1 SNP every 5 kilobases that is integrated with the human genome sequence and that is freely available in the public domain. 相似文献
72.
Jaime M Movshovich R Stewart GR Beyermann WP Berisso MG Hundley MF Canfield PC Sarrao JL 《Nature》2000,405(6783):160-163
Kondo insulator materials--such as CeRhAs, CeRhSb, YbB12, Ce3Bi4Pt3 and SmB6--are 3d, 4f and 5f intermetallic compounds that have attracted considerable interest in recent years. At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band at the Fermi energy and the materials become insulating. This contrasts with other f-electron compounds, which are metallic at all temperatures. The formation of the gap in Kondo insulators has been proposed to be a consequence of hybridization between the conduction band and the f-electron levels, giving a 'spin' gap. If this is indeed the case, metallic behaviour should be recovered when the gap is closed by changing external parameters, such as magnetic field or pressure. Some experimental evidence suggests that the gap can be closed in SmB6 (refs 5, 8) and YbB12 (ref. 9). Here we present specific-heat measurements of Ce3Bi4Pt3 in d.c. and pulsed magnetic fields up to 60 tesla. Numerical results and the analysis of our data using the Coqblin-Schrieffer model demonstrate unambiguously a field-induced insulator-to-metal transition. 相似文献
73.
R. Stewart 《Cellular and molecular life sciences : CMLS》1959,15(10):401-406
The emphasis placed on electron transfer in connection with oxidation reactions has often resulted in these processes being considered as a group apart from the main class of chemical reactions. Although some oxidations, for example certain exchange reactions between ions in solution, can be reasonably described as electron transfer processes, there are very many other oxidations, whose mechanisms are much better described in the familiar terms of modern organic chemistry.The use of isotopes as tracers has shown, that many oxidations proceed with transfer of atoms or groups from oxidant to reductant andvice versa; the use of the kinetic isotope effect has shown that such transfer is seldom an incidental process, but is almost always a part of the slow step of the reaction. In this paper, oxidations involving the transfer of such species as oxygen atoms, hydride ions, hydrogen atoms, chlorine atoms, and hydroxyl radicals are discussed in terms of mechanism. An attempt is made to show that a graded series of mechanisms is possible ranging from what appear to be pure electron transfer processes at one end to certain atom transfer processes at the other. The latter group belong, in fact, in the familiar realm of ordinary chemical raactions, in which strong bonds are being broken and formed in the activated complex.Contribution from Department of Chemistry, University of British Columbia, Vancouver. — Presented at the Organic Chemistry Symposium of the Chemical Institute of Canada, Ottawa, Dec. 8–9, 1958. 相似文献
74.
Atypical mast cell degranulation and focal hydropic degeneration of venular endothelium in diffuse fibrosing alveolitis 总被引:4,自引:0,他引:4
Atypical scroll-like and tubular degranulation of mast cells closely associated with focal endothelial hydropic degeneration is reported in human lung from 4 patients with diffuse fibrosing alveolitis in which the predominant abnormality was hyperplasia and desquamation of type 2 pneumocytes. 相似文献
75.
76.
77.
Denervation effects on choline depolarization of muscle membrane 总被引:1,自引:0,他引:1
A Portela R J Pérez R Nallar J C Pérez P Stewart J A Vincente P Lonchampt 《Experientia》1969,25(2):143-144
78.
Nitrogenase activity in heterocysts of blue-green algae 总被引:22,自引:0,他引:22
79.
Sarrao JL Morales LA Thompson JD Scott BL Stewart GR Wastin F Rebizant J Boulet P Colineau E Lander GH 《Nature》2002,420(6913):297-299
Plutonium is a metal of both technological relevance and fundamental scientific interest. Nevertheless, the electronic structure of plutonium, which directly influences its metallurgical properties, is poorly understood. For example, plutonium's 5f electrons are poised on the border between localized and itinerant, and their theoretical treatment pushes the limits of current electronic structure calculations. Here we extend the range of complexity exhibited by plutonium with the discovery of superconductivity in PuCoGa5. We argue that the observed superconductivity results directly from plutonium's anomalous electronic properties and as such serves as a bridge between two classes of spin-fluctuation-mediated superconductors: the known heavy-fermion superconductors and the high-T(c) copper oxides. We suggest that the mechanism of superconductivity is unconventional; seen in that context, the fact that the transition temperature, T(c) approximately 18.5 K, is an order of magnitude greater than the maximum seen in the U- and Ce-based heavy-fermion systems may be natural. The large critical current displayed by PuCoGa5, which comes from radiation-induced self damage that creates pinning centres, would be of technological importance for applied superconductivity if the hazardous material plutonium were not a constituent. 相似文献
80.
Van Eerdewegh P Little RD Dupuis J Del Mastro RG Falls K Simon J Torrey D Pandit S McKenny J Braunschweiger K Walsh A Liu Z Hayward B Folz C Manning SP Bawa A Saracino L Thackston M Benchekroun Y Capparell N Wang M Adair R Feng Y Dubois J FitzGerald MG Huang H Gibson R Allen KM Pedan A Danzig MR Umland SP Egan RW Cuss FM Rorke S Clough JB Holloway JW Holgate ST Keith TP 《Nature》2002,418(6896):426-430
Asthma is a common respiratory disorder characterized by recurrent episodes of coughing, wheezing and breathlessness. Although environmental factors such as allergen exposure are risk factors in the development of asthma, both twin and family studies point to a strong genetic component. To date, linkage studies have identified more than a dozen genomic regions linked to asthma. In this study, we performed a genome-wide scan on 460 Caucasian families and identified a locus on chromosome 20p13 that was linked to asthma (log(10) of the likelihood ratio (LOD), 2.94) and bronchial hyperresponsiveness (LOD, 3.93). A survey of 135 polymorphisms in 23 genes identified the ADAM33 gene as being significantly associated with asthma using case-control, transmission disequilibrium and haplotype analyses (P = 0.04 0.000003). ADAM proteins are membrane-anchored metalloproteases with diverse functions, which include the shedding of cell-surface proteins such as cytokines and cytokine receptors. The identification and characterization of ADAM33, a putative asthma susceptibility gene identified by positional cloning in an outbred population, should provide insights into the pathogenesis and natural history of this common disease. 相似文献