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91.
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
92.
Fairman ME Maroney PA Wang W Bowers HA Gollnick P Nilsen TW Jankowsky E 《Science (New York, N.Y.)》2004,304(5671):730-734
Members of the DExH/D superfamily of nucleic acid-activated nucleotide triphosphatases are essential for virtually all aspects of RNA metabolism, including pre-messenger RNA splicing, RNA interference, translation, and nucleocytoplasmic trafficking. Physiological substrates for these enzymes are thought to be regions of double-stranded RNA, because several DExH/D proteins catalyze strand separation in vitro. These "RNA helicases" can also disrupt RNA-protein interactions, but it is unclear whether this activity is coupled to duplex unwinding. Here we demonstrate that two unrelated DExH/D proteins catalyze protein displacement independently of duplex unwinding. Therefore, the essential functions of DExH/D proteins are not confined to RNA duplexes but can be exerted on a wide range of ribonucleoprotein substrates. 相似文献
93.
Michel JB Shen YK Aiden AP Veres A Gray MK;Google Books Team Pickett JP Hoiberg D Clancy D Norvig P Orwant J Pinker S Nowak MA Aiden EL 《Science (New York, N.Y.)》2011,331(6014):176-182
We constructed a corpus of digitized texts containing about 4% of all books ever printed. Analysis of this corpus enables us to investigate cultural trends quantitatively. We survey the vast terrain of 'culturomics,' focusing on linguistic and cultural phenomena that were reflected in the English language between 1800 and 2000. We show how this approach can provide insights about fields as diverse as lexicography, the evolution of grammar, collective memory, the adoption of technology, the pursuit of fame, censorship, and historical epidemiology. Culturomics extends the boundaries of rigorous quantitative inquiry to a wide array of new phenomena spanning the social sciences and the humanities. 相似文献
94.
Analysis of the subunit polypeptide composition of Fraction 1 proteins gives information on the expression of both nuclear and chloroplast genomes; the large subunits of the protein are coded by chloroplast DNA, whereas the small subunits are coded by nuclear DNA. Fraction 1 protein isolated from the leaves of parasexual hybrid plants derived from the fusion of protoplasts of Nicotiana glauca and N. langsdorffii contains the small subunit polypeptides of both parent species and the large subunit polypeptides of only N. glauca. Fraction 1 protein isolated from the leaves of a hybrid plant obtained after the uptake of chloroplasts of N. suaveolens by protoplasts of white tissue of a variegating mutant of N. tabacum contains the large subunit polypeptides of both N. suaveolens and N. tabacum, as well as the small subunit polypeptides of both these species. 相似文献
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Sutter NB Bustamante CD Chase K Gray MM Zhao K Zhu L Padhukasahasram B Karlins E Davis S Jones PG Quignon P Johnson GS Parker HG Fretwell N Mosher DS Lawler DF Satyaraj E Nordborg M Lark KG Wayne RK Ostrander EA 《Science (New York, N.Y.)》2007,316(5821):112-115
The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs. 相似文献
96.
Stem cell self-renewal can be specified by local signals from the surrounding microenvironment, or niche. However, the relation between the niche and the mechanisms that ensure the correct balance between stem cell self-renewal and differentiation is poorly understood. Here, we show that dividing Drosophila male germline stem cells use intracellular mechanisms involving centrosome function and cortically localized Adenomatous Polyposis Coli tumor suppressor protein to orient mitotic spindles perpendicular to the niche, ensuring a reliably asymmetric outcome in which one daughter cell remains in the niche and self-renews stem cell identity, whereas the other, displaced away, initiates differentiation. 相似文献
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Modern laser technology has revolutionized the sensitivity and precision of spectroscopy by providing coherent light in a spectrum spanning the infrared, visible, and ultraviolet wavelength regimes. However, the generation of shorter-wavelength coherent pulses in the x-ray region has proven much more challenging. The recent emergence of high harmonic generation techniques opens the door to this possibility. Here we review the new science that is enabled by an ability to manipulate and control electrons on attosecond time scales, ranging from new tabletop sources of coherent x-rays to an ability to follow complex electron dynamics in molecules and materials. We also explore the implications of these advances for the future of molecular structural characterization schemes that currently rely so heavily on scattering from incoherent x-ray sources. 相似文献