Drosophila CENH3 is sufficient for centromere formation     

Mendiburo MJ  Padeken J  Fülöp S  Schepers A  Heun P 《Science (New York, N.Y.)》2011,334(6056):686-690

CENH3 is a centromere-specific histone H3 variant essential for kinetochore assembly. Despite its central role in centromere function, there has been no conclusive evidence supporting CENH3 as sufficient to determine centromere identity. To address this question, we artificially targeted Drosophila CENH3 (CENP-A/CID) as a CID-GFP-LacI fusion protein to stably integrated lac operator (lacO) arrays. This ectopic CID focus assembles a functional kinetochore and directs incorporation of CID molecules without the LacI-anchor, providing evidence for the self-propagation of the epigenetic mark. CID-GFP-LacI-bound extrachromosomal lacO plasmids can assemble kinetochore proteins and bind microtubules, resulting in their stable transmission for several cell generations even after eliminating CID-GFP-LacI. We conclude that CID is both necessary and sufficient to serve as an epigenetic centromere mark and nucleate heritable centromere function.  相似文献   

Dictyota dichotoma (Phaeophyceae): Identification of the Sperm Attractant     

Müller DG  Gassmann G  Boland W  Marner F  Jaenicke L 《Science (New York, N.Y.)》1981,212(4498):1040-1041

Freshly released eggs of the marine brown alga Dictyota dichotoma secrete a substance that attracts spermatozoids. This compound has been identified as n-butyl-cyclohepta-2,5-diene. It is closely related to attractants in several other brown algae and confirms that a relation exists between phylogeny and attractant compounds.  相似文献   

Chemistry. The beauty of symmetry     

Müller A 《Science (New York, N.Y.)》2003,300(5620):749-750

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高校音乐资料的管理趋向分析     

杜金菊  刘海潮 《农业图书情报学刊》2006,18(1):34-36

针对当今信息时代信息传播和管理现状、音乐资料的特殊性以及信息化管理模式所具有的优越性三个方面进行分析，得出高校音乐资料的管理趋向是进行信息化管理模式。  相似文献   

Impaired immunoproteasome assembly and immune responses in PA28-/- mice     

Preckel T  Fung-Leung WP  Cai Z  Vitiello A  Salter-Cid L  Winqvist O  Wolfe TG  Von Herrath M  Angulo A  Ghazal P  Lee JD  Fourie AM  Wu Y  Pang J  Ngo K  Peterson PA  Früh K  Yang Y 《Science (New York, N.Y.)》1999,286(5447):2162-2165

In vitro PA28 binds and activates proteasomes. It is shown here that mice with a disrupted PA28b gene lack PA28a and PA28b polypeptides, demonstrating that PA28 functions as a hetero-oligomer in vivo. Processing of antigenic epitopes derived from exogenous or endogenous antigens is altered in PA28-/- mice. Cytotoxic T lymphocyte responses are impaired, and assembly of immunoproteasomes is greatly inhibited in mice lacking PA28. These results show that PA28 is necessary for immunoproteasome assembly and is required for efficient antigen processing, thus demonstrating the importance of PA28-mediated proteasome function in immune responses.  相似文献   

Cassini measurements of cold plasma in the ionosphere of Titan     

Wahlund JE  Boström R  Gustafsson G  Gurnett DA  Kurth WS  Pedersen A  Averkamp TF  Hospodarsky GB  Persoon AM  Canu P  Neubauer FM  Dougherty MK  Eriksson AI  Morooka MW  Gill R  André M  Eliasson L  Müller-Wodarg I 《Science (New York, N.Y.)》2005,308(5724):986-989

The Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) sensor observed the cold plasma environment around Titan during the first two flybys. The data show that conditions in Saturn's magnetosphere affect the structure and dynamics deep in the ionosphere of Titan. The maximum measured ionospheric electron number density reached 3800 per cubic centimeter near closest approach, and a complex chemistry was indicated. The electron temperature profiles are consistent with electron heat conduction from the hotter Titan wake. The ionospheric escape flux was estimated to be 10(25) ions per second.  相似文献   

Physiology. Turning on a dime     

Müller UK  Lentink D 《Science (New York, N.Y.)》2004,306(5703):1899-1900

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p53- and drug-induced apoptotic responses mediated by BH3-only proteins puma and noxa     

Villunger A  Michalak EM  Coultas L  Müllauer F  Böck G  Ausserlechner MJ  Adams JM  Strasser A 《Science (New York, N.Y.)》2003,302(5647):1036-1038

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30,000 years of hydrothermal activity at the lost city vent field     

Früh-Green GL  Kelley DS  Bernasconi SM  Karson JA  Ludwig KA  Butterfield DA  Boschi C  Proskurowski G 《Science (New York, N.Y.)》2003,301(5632):495-498

Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years.  相似文献   

Deciphering the reaction dynamics underlying optimal control laser fields     

Daniel C  Full J  González L  Lupulescu C  Manz J  Merli A  Vajda S  Wöste L 《Science (New York, N.Y.)》2003,299(5606):536-539

Femtosecond high-resolution pump-probe experiments have been used together with theoretical ab initio quantum calculations and wave packet dynamics simulations to decode an optimal femtosecond pulse that is generated from adaptive learning algorithms. This pulse is designed to maximize the yield of the organometallic ion CpMn(CO)3 while hindering the competing fragmentation. The sequential excitation and ionization of the target ion are accomplished by an optimized field consisting of two dominant subpulses with optimal frequencies and time delays.  相似文献