Retention of xenon in quartz and Earth's missing xenon     

Sanloup C  Schmidt BC  Chamorro Perez EM  Jambon A  Gregoryanz E  Mezouar M 《Science (New York, N.Y.)》2005,310(5751):1174-1177

The reactivity of xenon with terrestrial oxides was investigated by in situ synchrotron x-ray diffraction. At high temperature (T > 500 kelvin), some silicon was reduced, and the pressure stability of quartz was expanded, attesting to the substitution of some xenon for silicon. When the quartz was quenched, xenon diffused out and only a few weight percent remained trapped in samples. These results show that xenon can be covalently bonded to oxygen in quartz in the lower continental crust, providing an answer to the missing xenon problem; synthesis paths of rare gas compounds are also opened.  相似文献   

Involvement of mammalian Mus81 in genome integrity and tumor suppression     

McPherson JP  Lemmers B  Chahwan R  Pamidi A  Migon E  Matysiak-Zablocki E  Moynahan ME  Essers J  Hanada K  Poonepalli A  Sanchez-Sweatman O  Khokha R  Kanaar R  Jasin M  Hande MP  Hakem R 《Science (New York, N.Y.)》2004,304(5678):1822-1826

Mus81-Eme1 endonuclease has been implicated in the rescue of stalled replication forks and the resolution of meiotic recombination intermediates in yeast. We used gene targeting to study the physiological requirements of Mus81 in mammals. Mus81-/- mice are viable and fertile, which indicates that mammalian Mus81 is not essential for recombination processes associated with meiosis. Mus81-deficient mice and cells were hypersensitive to the DNA cross-linking agent mitomycin C but not to gamma-irradiation. Remarkably, both homozygous Mus81-/- and heterozygous Mus81+/- mice exhibited a similar susceptibility to spontaneous chromosomal damage and a profound and equivalent predisposition to lymphomas and other cancers. These studies demonstrate a critical role for the proper biallelic expression of the mammalian Mus81 in the maintenance of genomic integrity and tumor suppression.  相似文献   

Structure, function, and activator-induced conformations of the CRSP coactivator     

Taatjes DJ  Näär AM  Andel F  Nogales E  Tjian R 《Science (New York, N.Y.)》2002,295(5557):1058-1062

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Structural roles for human translation factor eIF3 in initiation of protein synthesis     

Siridechadilok B  Fraser CS  Hall RJ  Doudna JA  Nogales E 《Science (New York, N.Y.)》2005,310(5753):1513-1515

Protein synthesis in mammalian cells requires initiation factor eIF3, a approximately 750-kilodalton complex that controls assembly of 40S ribosomal subunits on messenger RNAs (mRNAs) bearing either a 5'-cap or an internal ribosome entry site (IRES). Cryo-electron microscopy reconstructions show that eIF3, a five-lobed particle, interacts with the hepatitis C virus (HCV) IRES RNA and the 5'-cap binding complex eIF4F via the same domain. Detailed modeling of eIF3 and eIF4F onto the 40S ribosomal subunit reveals that eIF3 uses eIF4F or the HCV IRES in structurally similar ways to position the mRNA strand near the exit site of 40S, promoting initiation complex assembly.  相似文献   

Ecology. A bid to save the 'Galápagos of the Indian Ocean'     

Sohlman E 《Science (New York, N.Y.)》2004,303(5665):1753

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Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage   总被引：3，自引：0，他引：3  

Dodd AN  Salathia N  Hall A  Kévei E  Tóth R  Nagy F  Hibberd JM  Millar AJ  Webb AA 《Science (New York, N.Y.)》2005,309(5734):630-633

Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control.  相似文献   

Buddenbrockia is a cnidarian worm     

Jiménez-Guri E  Philippe H  Okamura B  Holland PW 《Science (New York, N.Y.)》2007,317(5834):116-118

A major evolutionary divide occurs in the animal kingdom between the so-called radially symmetric animals, which includes the cnidarians, and the bilaterally symmetric animals, which includes all worm phyla. Buddenbrockia plumatellae is an active, muscular, parasitic worm that belongs to the phylum Myxozoa, a group of morphologically simplified microscopic endoparasites that has proved difficult to place phylogenetically. Phylogenetic analyses of multiple protein-coding genes demonstrate that Buddenbrockia is a cnidarian. This active muscular worm increases the known diversity in cnidarian body plans and demonstrates that a muscular, wormlike form can evolve in the absence of overt bilateral symmetry.  相似文献   

Cancer. Aneuploidy advantages?     

Hernando E 《Science (New York, N.Y.)》2008,322(5902):692-693

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Preindustrial to modern interdecadal variability in coral reef pH   总被引：1，自引：0，他引：1  

Pelejero C  Calvo E  McCulloch MT  Marshall JF  Gagan MK  Lough JM  Opdyke BN 《Science (New York, N.Y.)》2005,309(5744):2204-2207

The oceans are becoming more acidic due to absorption of anthropogenic carbon dioxide from the atmosphere. The impact of ocean acidification on marine ecosystems is unclear, but it will likely depend on species adaptability and the rate of change of seawater pH relative to its natural variability. To constrain the natural variability in reef-water pH, we measured boron isotopic compositions in a approximately 300-year-old massive Porites coral from the southwestern Pacific. Large variations in pH are found over approximately 50-year cycles that covary with the Interdecadal Pacific Oscillation of ocean-atmosphere anomalies, suggesting that natural pH cycles can modulate the impact of ocean acidification on coral reef ecosystems.  相似文献   

Control of stress-dependent cardiac growth and gene expression by a microRNA   总被引：2，自引：0，他引：2  

van Rooij E  Sutherland LB  Qi X  Richardson JA  Hill J  Olson EN 《Science (New York, N.Y.)》2007,316(5824):575-579

The heart responds to diverse forms of stress by hypertrophic growth accompanied by fibrosis and eventual diminution of contractility, which results from down-regulation of alpha-myosin heavy chain (alphaMHC) and up-regulation of betaMHC, the primary contractile proteins of the heart. We found that a cardiac-specific microRNA (miR-208) encoded by an intron of the alphaMHC gene is required for cardiomyocyte hypertrophy, fibrosis, and expression of betaMHC in response to stress and hypothyroidism. Thus, the alphaMHC gene, in addition to encoding a major cardiac contractile protein, regulates cardiac growth and gene expression in response to stress and hormonal signaling through miR-208.  相似文献