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121.
Structure of deoxymyoglobin: a crystallographic study 总被引:2,自引:0,他引:2
122.
Excess males among siblings of Australian antigen carriers 总被引:1,自引:0,他引:1
123.
The oxidation state of Hadean magmas and implications for early Earth's atmosphere 总被引:11,自引:0,他引:11
Magmatic outgassing of volatiles from Earth's interior probably played a critical part in determining the composition of the earliest atmosphere, more than 4,000 million years (Myr) ago. Given an elemental inventory of hydrogen, carbon, nitrogen, oxygen and sulphur, the identity of molecular species in gaseous volcanic emanations depends critically on the pressure (fugacity) of oxygen. Reduced melts having oxygen fugacities close to that defined by the iron-wüstite buffer would yield volatile species such as CH(4), H(2), H(2)S, NH(3) and CO, whereas melts close to the fayalite-magnetite-quartz buffer would be similar to present-day conditions and would be dominated by H(2)O, CO(2), SO(2) and N(2) (refs 1-4). Direct constraints on the oxidation state of terrestrial magmas before 3,850?Myr before present (that is, the Hadean eon) are tenuous because the rock record is sparse or absent. Samples from this earliest period of Earth's history are limited to igneous detrital zircons that pre-date the known rock record, with ages approaching ~4,400?Myr (refs 5-8). Here we report a redox-sensitive calibration to determine the oxidation state of Hadean magmatic melts that is based on the incorporation of cerium into zircon crystals. We find that the melts have average oxygen fugacities that are consistent with an oxidation state defined by the fayalite-magnetite-quartz buffer, similar to present-day conditions. Moreover, selected Hadean zircons (having chemical characteristics consistent with crystallization specifically from mantle-derived melts) suggest oxygen fugacities similar to those of Archaean and present-day mantle-derived lavas as early as ~4,350?Myr before present. These results suggest that outgassing of Earth's interior later than ~200?Myr into the history of Solar System formation would not have resulted in a reducing atmosphere. 相似文献
124.
Ley TJ Mardis ER Ding L Fulton B McLellan MD Chen K Dooling D Dunford-Shore BH McGrath S Hickenbotham M Cook L Abbott R Larson DE Koboldt DC Pohl C Smith S Hawkins A Abbott S Locke D Hillier LW Miner T Fulton L Magrini V Wylie T Glasscock J Conyers J Sander N Shi X Osborne JR Minx P Gordon D Chinwalla A Zhao Y Ries RE Payton JE Westervelt P Tomasson MH Watson M Baty J Ivanovich J Heath S Shannon WD Nagarajan R Walter MJ Link DC Graubert TA DiPersio JF Wilson RK 《Nature》2008,456(7218):66-72
Acute myeloid leukaemia is a highly malignant haematopoietic tumour that affects about 13,000 adults in the United States each year. The treatment of this disease has changed little in the past two decades, because most of the genetic events that initiate the disease remain undiscovered. Whole-genome sequencing is now possible at a reasonable cost and timeframe to use this approach for the unbiased discovery of tumour-specific somatic mutations that alter the protein-coding genes. Here we present the results obtained from sequencing a typical acute myeloid leukaemia genome, and its matched normal counterpart obtained from the same patient's skin. We discovered ten genes with acquired mutations; two were previously described mutations that are thought to contribute to tumour progression, and eight were new mutations present in virtually all tumour cells at presentation and relapse, the function of which is not yet known. Our study establishes whole-genome sequencing as an unbiased method for discovering cancer-initiating mutations in previously unidentified genes that may respond to targeted therapies. 相似文献
125.