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61.
Somatic cell nuclear transfer 总被引:30,自引:0,他引:30
Wilmut I Beaujean N de Sousa PA Dinnyes A King TJ Paterson LA Wells DN Young LE 《Nature》2002,419(6907):583-586
Cloning by nuclear transfer from adult somatic cells is a remarkable demonstration of developmental plasticity. When a nucleus is placed in oocyte cytoplasm, the changes in chromatin structure that govern differentiation can be reversed, and the nucleus can be made to control development to term. 相似文献
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R. Kazlauskas P. T. Murphy R. J. Wells 《Cellular and molecular life sciences : CMLS》1980,36(7):814-815
Summary The structure of furodendin (5), a minor secondary metabolite of the spongePhyllospongia dendyi, has been solved by spectral methods. Furodendin is probably derived, biosynthetically, by elimination of a C3 unit from a C25 geranyl-farnesol precursor.Acknowledgment. We thank Dr C. Evans for sponge identification, RRIMP Museum number FN 1516/000. 相似文献
66.
Y chromosome sequence variation and the history of human populations 总被引:48,自引:0,他引:48
Underhill PA Shen P Lin AA Jin L Passarino G Yang WH Kauffman E Bonné-Tamir B Bertranpetit J Francalacci P Ibrahim M Jenkins T Kidd JR Mehdi SQ Seielstad MT Wells RS Piazza A Davis RW Feldman MW Cavalli-Sforza LL Oefner PJ 《Nature genetics》2000,26(3):358-361
Binary polymorphisms associated with the non-recombining region of the human Y chromosome (NRY) preserve the paternal genetic legacy of our species that has persisted to the present, permitting inference of human evolution, population affinity and demographic history. We used denaturing high-performance liquid chromatography (DHPLC; ref. 2) to identify 160 of the 166 bi-allelic and 1 tri-allelic site that formed a parsimonious genealogy of 116 haplotypes, several of which display distinct population affinities based on the analysis of 1062 globally representative individuals. A minority of contemporary East Africans and Khoisan represent the descendants of the most ancestral patrilineages of anatomically modern humans that left Africa between 35,000 and 89,000 years ago. 相似文献
67.
Campana S Mangano V Blustin AJ Brown P Burrows DN Chincarini G Cummings JR Cusumano G Della Valle M Malesani D Mészáros P Nousek JA Page M Sakamoto T Waxman E Zhang B Dai ZG Gehrels N Immler S Marshall FE Mason KO Moretti A O'Brien PT Osborne JP Page KL Romano P Roming PW Tagliaferri G Cominsky LR Giommi P Godet O Kennea JA Krimm H Angelini L Barthelmy SD Boyd PT Palmer DM Wells AA White NE 《Nature》2006,442(7106):1008-1010
Although the link between long gamma-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a gamma-ray burst emerges from the star's surface, nor how a GRB progenitor explodes. Here we report observations of the relatively nearby GRB 060218 (ref. 5) and its connection to supernova SN 2006aj (ref. 6). In addition to the classical non-thermal emission, GRB 060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/ultraviolet band as time passes. We interpret these features as arising from the break-out of a shock wave driven by a mildly relativistic shell into the dense wind surrounding the progenitor. We have caught a supernova in the act of exploding, directly observing the shock break-out, which indicates that the GRB progenitor was a Wolf-Rayet star. 相似文献
68.
Klussmann M Iwamura H Mathew SP Wells DH Pandya U Armstrong A Blackmond DG 《Nature》2006,441(7093):621-623
Ever since Pasteur noticed that tartrate crystals exist in two non-superimposable forms that are mirror images of one another--as are left and right hands--the phenomenon of chirality has intrigued scientists. On the molecular level, chirality often has a profound impact on recognition and interaction events and is thus important to biochemistry and pharmacology. In chemical synthesis, much effort has been directed towards developing asymmetric synthesis strategies that yield product molecules with a significant excess of either the left-handed or right-handed enantiomer. This is usually achieved by making use of chiral auxiliaries or catalysts that influence the course of a reaction, with the enantiomeric excess (ee) of the product linearly related to the ee of the auxiliary or catalyst used. In recent years, however, an increasing number of asymmetric reactions have been documented where this relationship is nonlinear, an effect that can lead to asymmetric amplification. Theoretical models have long suggested that autocatalytic processes can result in kinetically controlled asymmetric amplification, a prediction that has now been verified experimentally and rationalized mechanistically for an autocatalytic alkylation reaction. Here we show an alternative mechanism that gives rise to asymmetric amplification based on the equilibrium solid-liquid phase behaviour of amino acids in solution. This amplification mechanism is robust and can operate in aqueous systems, making it an appealing proposition for explaining one of the most tantalizing examples of asymmetric amplification-the development of high enantiomeric excess in biomolecules from a presumably racemic prebiotic world. 相似文献
69.
Cusumano G Mangano V Chincarini G Panaitescu A Burrows DN La Parola V Sakamoto T Campana S Mineo T Tagliaferri G Angelini L Barthelemy SD Beardmore AP Boyd PT Cominsky LR Gronwall C Fenimore EE Gehrels N Giommi P Goad M Hurley K Kennea JA Mason KO Marshall F Mészáros P Nousek JA Osborne JP Palmer DM Roming PW Wells A White NE Zhang B 《Nature》2006,440(7081):164
Long gamma-ray bursts (GRBs) are bright flashes of high-energy photons that can last for tens of minutes; they are generally associated with galaxies that have a high rate of star formation and probably arise from the collapsing cores of massive stars, which produce highly relativistic jets (collapsar model). Here we describe gamma- and X-ray observations of the most distant GRB ever observed (GRB 050904): its redshift (z) of 6.29 means that this explosion happened 12.8 billion years ago, corresponding to a time when the Universe was just 890 million years old, close to the reionization era. This means that not only did stars form in this short period of time after the Big Bang, but also that enough time had elapsed for them to evolve and collapse into black holes. 相似文献