A chromium terephthalate-based solid with unusually large pore volumes and surface area   总被引：2，自引：0，他引：2  

Férey G  Mellot-Draznieks C  Serre C  Millange F  Dutour J  Surblé S  Margiolaki I 《Science (New York, N.Y.)》2005,309(5743):2040-2042

We combined targeted chemistry and computational design to create a crystal structure for porous chromium terephthalate, MIL-101, with very large pore sizes and surface area. Its zeotype cubic structure has a giant cell volume (approximately 702,000 cubic angstroms), a hierarchy of extra-large pore sizes (approximately 30 to 34 angstroms), and a Langmuir surface area for N2 of approximately 5900 +/- 300 square meters per gram. Beside the usual properties of porous compounds, this solid has potential as a nanomold for monodisperse nanomaterials, as illustrated here by the incorporation of Keggin polyanions within the cages.  相似文献   

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   

NSP1 of the GRAS protein family is essential for rhizobial Nod factor-induced transcription   总被引：1，自引：0，他引：1  

Smit P  Raedts J  Portyanko V  Debellé F  Gough C  Bisseling T  Geurts R 《Science (New York, N.Y.)》2005,308(5729):1789-1791

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Energetics of load carrying in Nepalese porters     

Bastien GJ  Schepens B  Willems PA  Heglund NC 《Science (New York, N.Y.)》2005,308(5729):1755

Nepalese porters routinely carry head-supported loads equal to 100 to 200% of their body weight (Mb) for many days up and down steep mountain footpaths at high altitudes. Previous studies have shown that African women carry head-supported loads of up to 60% of their Mb far more economically than army recruits carrying equivalent loads in backpacks. Here we show that Nepalese porters carry heavier loads even more economically than African women. Female Nepalese porters, for example, carry on average loads that are 10% of their Mb heavier than the maximum loads carried by the African women, yet do so at a 25% smaller metabolic cost.  相似文献   

German funding for sonne expedition     

Devey C  Hékinian R 《Science (New York, N.Y.)》1995,269(5224):621

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Comment on "Status and trends of amphibian declines and extinctions worldwide"     

Pimenta BV  Haddad CF  Nascimento LB  Cruz CA  Pombal JP 《Science (New York, N.Y.)》2005,309(5743):1999; author reply 1999

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Molecular geometry and nonlinear optics     

Brédas JL 《Science (New York, N.Y.)》1994,263(5146):487-488

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Noise in gene expression determines cell fate in Bacillus subtilis     

Maamar H  Raj A  Dubnau D 《Science (New York, N.Y.)》2007,317(5837):526-529

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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   

The proteasome of Mycobacterium tuberculosis is required for resistance to nitric oxide     

Darwin KH  Ehrt S  Gutierrez-Ramos JC  Weich N  Nathan CF 《Science (New York, N.Y.)》2003,302(5652):1963-1966

The production of nitric oxide and other reactive nitrogen intermediates (RNI) by macrophages helps to control infection by Mycobacterium tuberculosis (Mtb). However, the protection is imperfect and infection persists. To identify genes that Mtb requires to resist RNI, we screened 10,100 Mtb transposon mutants for hypersusceptibility to acidified nitrite. We found 12 mutants with insertions in seven genes representing six pathways, including the repair of DNA (uvrB) and the synthesis of a flavin cofactor (fbiC). Five mutants had insertions in proteasome-associated genes. An Mtb mutant deficient in a presumptive proteasomal adenosine triphosphatase was attenuated in mice, and exposure to proteasomal protease inhibitors markedly sensitized wild-type Mtb to RNI. Thus, the mycobacterial proteasome serves as a defense against oxidative or nitrosative stress.  相似文献