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Nature Contents 7 September 2006 (Vol. 443 pp1-120)
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=================================== Nature 443: 7107 7 September 2006 =================================== [自然要览] （选自英国Nature杂志，2006年9月7日出版） 封面故事：影响精子生成的因子 Sperm chromatin proteomics identifies evolutionarily conserved fertility factors 利用基因组学方法对线虫（Caenorhabditis elegans）所做的一项研究工作，识 别出了DNA压缩、染色体分离和生育能力所需要的专门针对精子生成的因子，其 中很多会引起小鼠雄性不育。该研究所获得的结果为识别雄性不育的原因提供了 新机会，为男性避孕提供了可能的目标。本期封面所示为线虫的一个雄性性腺中 的细胞核正在经历精子生成过程，该性腺已被固定，并用荧光标记物染了色。图 中所示DNA为红色，组蛋白H2A的变体HTAS-1的存在示为绿色，图中的黄色表示位 置重叠（colocalization）。（Letter p. 101） 音乐为什么动听？（soothing the savage breast） Hitting the right note 为什么音乐令人愉快？其精神吸引力是什么？这些都是认知学研究人员David Huron在《甜蜜的预期：音乐和期待的心理》一书中所探讨的主题。我们的书评 员称该书是“探寻音乐内在奥秘的一次迷人旅程”。在您阅读该书评的时候，您 可以把Huron的试验乐曲作为背景音乐来播放（网址是 http://tinyurl.com/lmjwl）。（Books and Arts p. 29） 神经氨酸苷酶N1、N4 和N8的结构被确定（Tackling the H5N1 virus） The structure of H5N1 avian influenza neuraminidase suggests new opportunities for drug design H5N1禽流感病毒是根据该病毒衣壳上的血凝素（H）和神经氨酸苷酶（N）蛋白命 名的，每个蛋白都有几种不同形式。神经氨酸苷酶帮助该病毒逃脱被感染的细胞 并进攻新的细胞，是Tamiflu (oseltamivir) 和 Relenza (zanamivir)的作用目 标。这些药物是根据神经氨酸苷酶N2 和N9的晶体结构设计的，是当时唯一可以 获得的这种结构。现在，N1、N4 和N8的结构也已经确定。与以前的结构相比， 它们都有一个关键的区别：在活性点的一个角上有一个空腔，该空腔闭合后就可 以锁定到其目标上。设计用来寻找这一活性点的药物也许可以利用该结构，从而 也许可避免某些病毒对Tamiflu所形成的药物抗性。（Article p. 45; N&V） 粘性突变的原因（A sticky wicket） Editing-defective tRNA synthetase causes protein misfolding and neurodegeneration 不久前，“粘性”小鼠突变体还主要因其皮毛不整洁的、“粘性”的外表为人们 所知。这种突变小鼠也会逐渐失去其毛发。在6个星期大的时候，在受到刺激时 它会轻轻颤抖，8个星期大时，它开始出现渐进性共济失调。这与其小脑中 Purkinje细胞的丢失在时间上是一致的。现在，粘性突变已被发现是丙氨酰转移 RNA合成酶所发生的一个单核苷变化。随后出现的转录失真和蛋白误折叠引起细 胞死亡，因为异常蛋白在神经细胞中累积。很多人类疾病与蛋白误折叠和神经细 胞损失有关，粘性小鼠的性质说明，这些疾病中有些可能是由于能够破坏tRNA合 成酶的突变。（Article p. 50; N&V） 小行星表面的太空风化现象（Asteroids under the weather） Developing space weathering on the asteroid 25143 Itokawa 我们会以为普通球粒状陨石（最丰富的陨石类型）母体在太阳系的小行星中很 多。但在主小行星带中占主导地位的S-型小行星看起来不像母体物质。一个可能 的解释是，母体的表面因“太空风化”作用而发生了光学变化。该理论因在很小 的小行星Itokawa（直径500米）上发现高度太空风化现象而获得了证据支持，而 该发现是根据由Hayabusa小行星相会飞船发回的数据获得的。（Letter p. 56） 涡流持续的时间（Turbulence times） Finite lifetime of turbulence in shear flows 大多数“流”在性质上是涡流，如大气中的气流、海洋中的洋流、行星核心的液 流、以及车辆周围的气流等。人们普遍接受的观点是，如果一个（稳定驱动的） 流变成了涡流，它将无限期地保持在这种状态。用一个在自然界有很多对应体系 的体系（穿过直管和通道流动的一种液体）所做的新的研究工作，得到一个令人 吃惊的结果：涡动在经过一个有限的时间后会衰减。尽管是有限的，但涡流的寿 命会随流速的增加而迅速增加，甚至在中等流速时也能具有无法观测的长时间尺 度。不过，该发现有可能被用来控制涡流。（Letter p. 59; N&V） 钴聚咇咯复合材料燃料电池催化剂（Towards affordable fuel cells） A class of non-precious metal composite catalysts for fuel cells 聚合物电解膜燃料电池显示了其作为一种未来能源的潜力，但它们的成本仍然太 高，无法实现商业应用，部分原因是需要基于铂的催化剂。现在，洛斯*阿拉莫 斯国家实验室的研究人员开发出一类新的不含贵金属的低成本催化剂，它们有可 能最终导致更加便宜的燃料电池的问世。这些新材料是钴聚咇咯复合材料，能够 催化聚合物电解燃料电池阴极上的氧还原反应。它们目前的催化性能还没有铂那 么好，但它们在高电压下在氢-氧燃料电池中的表现具有可重复性，稳定性也很 好。（Letter p. 63） 能催化手性反应的一种不含金属的催化剂（Chiral synthesis made easy） Enantioselective silyl protection of alcohols catalysed by an amino-acid-based small molecule 可靠的、具有选择性的、对环境友好的化学反应，是有效合成天然产物和治疗药 物所经常需要的。尽管对这种合成反应有若干催化剂可供使用，但化学家却经常 在寻找能以高产率和高对映纯度生成有机分子的新催化剂。现在，Zhao等人开发 出了一种简单的不含金属的催化剂，可用来利用一个甲硅烷基保护基团来保护一 个特定的醇分子，而不会改变附近的另一个醇分子。对若干种基质，他们都获得 了高产率和对映异构体。他们希望，该催化剂可导致能够生成重要有机分子的一 组新的“绿色”催化剂的诞生。（Letter p. 67; News and Views） 湖泊消融所产生甲烷对全球变暖的贡献（Strange brew） Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming 当冻土沿北西伯利亚的湖泊边缘消融时，死亡的植物和动物遗体会掉到湖床上， 在那里，它们会分解，产生甲烷，后者是一种强效温室气体。甲烷以气泡形式上 升到湖泊表面，进入大气，加重全球变暖。此前，这些气泡的相对重要性一直不 确定，因为该现象的零散使得人们难以对它进行测量。对西伯利亚湖泊所做的一 项新的研究表明，湖泊中气泡的形成对大气中甲烷来源的贡献要比以前所认为的 更大，需要将目前关于来自北半球湿地的排放量的估计数字提高10%到63%。该地 区消融湖泊面积最近的扩大可能会明显增加甲烷的排放，说明湖泊消融所产生的 甲烷可能是对全球变暖的一个正反馈。（Letter p. 71） 性的演化起源问题（The question of sex） Interference among deleterious mutations favours sex and recombination in finite populations 几十年来，科学家一直在寻找有利于性的出现和重组的演化力量。将有害突变从 基因组中清除的需要，是一个可能的推动力。这种说法如果是对的话，那么有害 突变可能需要表现出负面的异位显性，也就是说，它们可能需要协同发挥作用， 来产生一个较大的累积效应。然而，实验证据表明，负面的异位显性在有害突变 中不普遍。现在，利用一个被称为Hill-Robertson干涉的概念，Peter Keightley 和Sarah Otto开发出一个电脑模型，它在选择重组时不管有害突变是 否变现出异位显性。这个结果为重组的演化、也许还包括性的演化提供了一个可 信的解释。（Letter p. 89） 用硝酸盐代替氧来呼吸的生物（Living without oxygen） Evidence for complete denitrification in a benthic foraminifer 几种有孔虫目的原生动物可在海洋沉积物中的缺氧区生长，但过去，维持它们生 存的缺氧呼吸的精确性质我们却不知道。现在，研究表明，这些生物能在细胞内 以比环境值高500倍的浓度积累硝酸盐。在这些缺氧生境中，硝酸盐可以代替 氧。所积累的大量硝酸盐甚至还使它们能够“屏住呼吸”超过一个月时间。 （Letter p. 93） 与茁长素输送有关的一种内体腔室（auxin actions） AtSNX1 defines an endosome for auxin-carrier trafficking in Arabidopsis 植物的生长和发育依赖于植物激素茁长素的水平和分布。植物细胞中茁长素的输 送受到各种不同的胞质膜茁长素载体的高度调控。现在，Jailais等人发现了一 个新的细胞外腔室，即SNX1内体腔室，它参与了这些茁长素中其中一种的输送。 过去，人们知道内体是动物信号作用中的关键成分，但该研究是首次表明它在植 物中也起一个相似的作用。（Letter p. 106） RNA酶-II的晶体结构（Class action） Unravelling the dynamics of RNA degradation by ribonuclease II and its RNA-bound complex 由II-类RNA酶家族的成员对RNA的降解，在RNA的成熟、周转和质量控制中起着根 本性的作用。现在，一种RNA酶-II的晶体结构已被首次确定，它以两种形式存 在：一种是与RNA结合的形式，另一种是没有配体的形式。出乎意料的是，该结 构并不与序列分析所预测的结构相对应。该分子有两个点与RNA相接触：一个点 固定RNA，另一个点催化解理反应。该结构细节可解释为什么RNA酶-II只对单链 RNA发生作用，也可解释它是怎样沿RNA前进、并逐渐对其进行降解的。（Letter p. 110） |
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ningkeqing
木虫 (正式写手)
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---------------------- NEWS AND VIEWS ---------------------- Cancer biology: Infectious tumour cells Cancer cells are generally viewed as a problem innate to their host, but evidence is mounting that they can evolve to become infectious agents and be transmitted between individuals. David Dingli and Martin A. Nowak 10.1038/443035a http://www.nature.com/nature/journal/v443/n7107/full/443035a.html Fluid dynamics: Turbulence lost in transience Turbulence is generally regarded as a permanent feature of many fluid flows. That assumption is challenged by the claim that shear turbulence has a limited lifetime -- albeit sometimes a very long one. Daniel Perry Lathrop 10.1038/443036a http://www.nature.com/nature/journal/v443/n7107/full/443036a.html Structural biology: Antiviral drugs fit for a purpose Did drug researchers have a lucky break when they developed antiviral drugs for influenza? Crystal structures of enzymes from the H5N1 virus suggest that they did, and provide avenues for further exploration. Ming Luo 10.1038/nature05003 http://www.nature.com/nature/jou ... ll/nature05003.html Mathematics: Controlling our errors The Sato-Tate conjecture holds that the error term occurring in many important problems in number theory conforms to a specific probability distribution. That conjecture has now been proved for a large group of cases. Barry Mazur 10.1038/443038a http://www.nature.com/nature/journal/v443/n7107/full/443038a.html Analytical chemistry: Playing molecular tag Richard Webb 10.1038/443039a http://www.nature.com/nature/journal/v443/n7107/full/443039a.html 50 & 100 years ago 10.1038/443040a http://www.nature.com/nature/journal/v443/n7107/full/443040a.html Organic chemistry: Catalysts break symmetry The creation of asymmetric molecules from symmetrical precursors is a useful strategy for organic synthesis. A new catalyst can accomplish this task through a unique, symmetry-breaking reaction. Scott E. Denmark 10.1038/443040b http://www.nature.com/nature/journal/v443/n7107/full/443040b.html Molecular biology: Sticky end in protein synthesis It's not clear what general level of accuracy is required in translating the genetic code. But the protective role of proof-reading is evident from a case in which a small mistake has a catastrophic effect. Herve Roy and Michael Ibba 10.1038/nature05002 http://www.nature.com/nature/jou ... ll/nature05002.html ---------------------- BRIEF COMMUNICATIONS ---------------------- Nitrogen balance and Arctic throughflow Waters moving east through the Arctic Ocean significantly contribute to nitrogen fixation in the Atlantic. Michiyo Yamamoto-Kawai, Eddy Carmack and Fiona McLaughlin 10.1038/443043a http://www.nature.com/nature/journal/v443/n7107/full/443043a.html BRIEF COMMUNICATIONS ARISING Planetary science: Bedrock formation at Meridiani Planum S. W. Squyres et al. 10.1038/nature05212 Abstract: http://www.nature.com/nature/jou ... bs/nature05212.html Article: http://www.nature.com/nature/jou ... ll/nature05212.html Planetary science: Bedrock formation at Meridiani Planum (Reply) Thomas M. McCollom and Brian M. Hynek 10.1038/nature05213 Abstract: http://www.nature.com/nature/jou ... bs/nature05213.html Article: http://www.nature.com/nature/jou ... ll/nature05213.html ---------------------- ARTICLES ---------------------- The structure of H5N1 avian influenza neuraminidase suggests new opportunities for drug design Rupert J. Russell et al. 10.1038/nature05114 Abstract: http://www.nature.com/nature/jou ... bs/nature05114.html Article: http://www.nature.com/nature/jou ... ll/nature05114.html Editing-defective tRNA synthetase causes protein misfolding and neurodegeneration In mice with the sticky mutation, the cells that are involved in motor coordination degenerate, due to a single nucleotide change in the enzyme called alanyl-tRNA synthetase. This demonstrates the potentially catastrophic consequences of small changes in the fidelity of translation. Jeong Woong Lee et al. 10.1038/nature05096 Abstract: http://www.nature.com/nature/jou ... bs/nature05096.html Article: http://www.nature.com/nature/jou ... ll/nature05096.html ---------------------- LETTERS ---------------------- Developing space weathering on the asteroid 25143 Itokawa A dark region on a small (550-metre) asteroid, 25143 Itokawa, is significantly more space-weathered than a nearby bright region. This shows that space-weathered materials accumulate on small asteroids. Takahiro Hiroi et al. 10.1038/nature05073 Abstract: http://www.nature.com/nature/jou ... bs/nature05073.html Article: http://www.nature.com/nature/jou ... ll/nature05073.html Finite lifetime of turbulence in shear flows The flow of a fluid down a straight pipe provides an example of a shear flow undergoing a sudden transition from laminar to turbulent motion. Experimental data and numerical calculations show that the lifetime of the turbulent state does not diverge, but rather increases exponentially with the Reynolds number. Bjorn Hof, Jerry Westerweel, Tobias M. Schneider and Bruno Eckhardt 10.1038/nature05089 Abstract: http://www.nature.com/nature/jou ... bs/nature05089.html Article: http://www.nature.com/nature/jou ... ll/nature05089.html A class of non-precious metal composite catalysts for fuel cells A new class of low-cost, non-precious-metal-polymer composite catalysts has been developed. These are not yet as good as platinum, but perform reproducibly in H2-O2 fuel cells at high voltages and with good stability. Rajesh Bashyam and Piotr Zelenay 10.1038/nature05118 Abstract: http://www.nature.com/nature/jou ... bs/nature05118.html Article: http://www.nature.com/nature/jou ... ll/nature05118.html Enantioselective silyl protection of alcohols catalysed by an amino-acid-based small molecule This study describes a simple catalyst that can be used to protect secondary alcohols with a silyl protecting group. High yields and enantioselectivies for a number of substrates were obtained. This, and related, catalysts may be used to synthesize, in a more practical and efficient manner, important organic molecules. Yu Zhao, Jason Rodrigo, Amir H. Hoveyda and Marc L. Snapper 10.1038/nature05102 Abstract: http://www.nature.com/nature/jou ... bs/nature05102.html Article: http://www.nature.com/nature/jou ... ll/nature05102.html Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming Lakes formed by thawing of frozen ground in North Siberia emit methane through bubbling. Now this flux has been quantified, revealing that it may be five times higher than previously thought, requiring current estimates of methane emissions from northern wetlands to be increased by 10-63%. K. M. Walter et al. 10.1038/nature05040 Abstract: http://www.nature.com/nature/jou ... bs/nature05040.html Article: http://www.nature.com/nature/jou ... ll/nature05040.html Magma heating by decompression-driven crystallization beneath andesite volcanoes Jon Blundy, Kathy Cashman and Madeleine Humphreys 10.1038/nature05100 Abstract: http://www.nature.com/nature/jou ... bs/nature05100.html Article: http://www.nature.com/nature/jou ... ll/nature05100.html Potentiation of cortical inhibition by visual deprivation An investigation of how cortical circuitry changes after a major manipulation of sensory input finds changes in cortical inhibitory circuitry. Out of the investigation also comes the description of a new form of synaptic plasticity between inhibitory interneurons and their targets. Arianna Maffei, Kiran Nataraj, Sacha B. Nelson and Gina G. Turrigiano 10.1038/nature05079 Abstract: http://www.nature.com/nature/jou ... bs/nature05079.html Article: http://www.nature.com/nature/jou ... ll/nature05079.html Experience-dependent representation of visual categories in parietal cortex In monkeys trained to categorize motion direction, two cortical motion-processing areas were found to carry category information to different degrees: lateral intraparietal neurons responded to direction depending on their category membership whereas middle temporal neurons encoded only direction. David J. Freedman and John A. Assad 10.1038/nature05078 Abstract: http://www.nature.com/nature/jou ... bs/nature05078.html Article: http://www.nature.com/nature/jou ... ll/nature05078.html Interference among deleterious mutations favours sex and recombination in finite populations By invoking a concept called Hill-Robertson interference, a computer simulation has been developed that selects for recombination regardless of whether deleterious mutations exhibit epistasis. This provides a new framework for understanding how recombination may have evolved. Peter D. Keightley and Sarah P. Otto 10.1038/nature05049 Abstract: http://www.nature.com/nature/jou ... bs/nature05049.html Article: http://www.nature.com/nature/jou ... ll/nature05049.html Evidence for complete denitrification in a benthic foraminifer Denitrification, the biological conversion of nitrate to nitrogen, was believed to be restricted to bacteria and archaea. It has now been shown that highly abundant benthic foraminifers are also capable of denitrification, suggesting that much remains to be learned about the global nitrogen cycle. Nils Risgaard-Petersen et al. 10.1038/nature05070 Abstract: http://www.nature.com/nature/jou ... bs/nature05070.html Article: http://www.nature.com/nature/jou ... ll/nature05070.html Soma-germline interactions coordinate homeostasis and growth in the Drosophila gonad Examining how the division rate of primordial germ cells (PGCs) in the fly ovary is controlled finds that there is a feedback loop composed of positive and negative signals, whereby PGCs express an EGF ligand called Spitz, which is essential for survival of adjacent somatic cells, and the somatic cells in turn inhibit PGC proliferation. Lilach Gilboa and Ruth Lehmann 10.1038/nature05068 Abstract: http://www.nature.com/nature/jou ... bs/nature05068.html Article: http://www.nature.com/nature/jou ... ll/nature05068.html Sperm chromatin proteomics identifies evolutionarily conserved fertility factors A proteomics strategy in Caenorhabditis elegans has identified spermatogenesis-specific factors required for DNA compaction, chromosome segregation and fertility, many of which cause male sterility in mice. Diana S. Chu et al. 10.1038/nature05050 Abstract: http://www.nature.com/nature/jou ... bs/nature05050.html Article: http://www.nature.com/nature/jou ... ll/nature05050.html AtSNX1 defines an endosome for auxin-carrier trafficking in Arabidopsis Trafficking of the phytohormone auxin throughout plant cells is highly regulated by a variety of plasma membrane auxin carriers. This study reports the discovery of a new intracellular compartment, the SNX1 endosomal compartment, which is involved in the trafficking of one of these auxin carriers. Yvon Jaillais et al. 10.1038/nature05046 Abstract: http://www.nature.com/nature/jou ... bs/nature05046.html Article: http://www.nature.com/nature/jou ... ll/nature05046.html Unravelling the dynamics of RNA degradation by ribonuclease II and its RNA-bound complex Determination of the first structure for an RNase II in the absence and presence of RNA reveals that the domain structure is different than sequence analysis had predicted. The structural details explain why RNase II only acts on single-stranded RNA, and how it moves along the RNA to processively degrade it. Carlos Frazao et al. 10.1038/nature05080 Abstract: http://www.nature.com/nature/jou ... bs/nature05080.html Article: http://www.nature.com/nature/jou ... ll/nature05080.html [ Last edited by mainpro on 2006-9-9 at 22:59 ] |
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