Volume 439 Number 7076 pp509-632封面故事：无二十面体对称性的球形病毒的结构
球形病毒结构的确定目前仅限于具有二十面体对称的衣壳。现在，研究人员首次确定了一个完整的、没有二十面体对称的球形病毒的结构，这种方法是简化图像重建计算所必需的。被确定结构的这个病毒是“epsilon15噬菌体”，它感染人类病原体“鸭沙门氏菌”（Salmonella anatum），所以是沙门氏菌病的一个潜在的治疗药物。单粒子冷电子显微镜研究显示，这个二十面体蛋白壳由60个六聚体和11个五聚体组成（见封面图片）。非二十面体的部分聚集在12个衣壳定点中的一个上，DNA通过这些定点被包裹起来和释放出去。该病毒的基因组在共轴“线圈”结构中，一个以前未被识别出来的蛋白锥包裹在DNA的端点上。该衣壳与包括疱疹病毒在内的其他dsDNA病毒的衣壳相似，说明它们有共同的祖先。
DNA复制过程怎样保证准确性
准确的DNA复制对所有生物的繁殖来说都至关重要。本期Nature上三篇论文和网上的一篇新的Web Focus文章（网址：），回答了关于一个DNA复制叉上发生了什么过程来保证这种准确性的长期未能回答的问题。有这么一个事实：即便是严重受损的DNA也能高速复制。Heller 和 Marians对这个现象做出了解释。他们发现，细菌复制重启系统能够通过DnaG 引发酶引发DNA前面的链和后面的链。这与已被人们接受的观点是矛盾的。该观点认为，DNA前面的链的合成必需是连续的。因此，该发现可能迫使科学家对关于染色体复制的引发方式的模型重新进行评估。Zenkin等人解开了由RNA聚合酶合成的一个短的转录链何以能够成为DNA复制的一个引发物的谜团。答案在于一个以前不知道的转录伸长复合物类型，这个复合物还可能联系着DNA复制和转录的机械系统。Lee等人要解决的问题是，在DNA前链和后链上发生的很不相同的过程是怎样同步的。在引发物被合成的时候，DNA引发酶起一个分子刹车的作用，在后链酶过程比较慢的时候使前链聚合酶的进程暂停。
果蝇的视觉记忆本领
同人类一样，果蝇也能识别和记忆视觉标志，它们能识别出物体的排列模式（如垂直的或倾斜的棒状物），而不管这些物体第一次是从哪里投射到视网膜上的。在利用基因操纵方法和一个果蝇飞行模拟器所做的一项实验中，研究人员首次在一个昆虫中发现了这些视觉记忆本领所需的神经细胞。他们发现，两组约20个神经细胞存在于“扇形体”内的两个窄层中，它是节肢动物大脑典型的中央复合体中的最大部分。中央复合体的功能过去曾被认为主要是集成两个脑半球中的信息，这项新的研究是首次将明确的行为功能归功于这一大脑区域。
海王星外天体2003 UB313的准确大小
2005年7月海王星外天体2003 UB313的发现，重新点燃了关于什么天体应被称为行星的讨论。这个海王星外天体被俗称为 “第10颗行星” （非正式名称），其光学亮度表明它比冥王星大，但由于不知道它的表面反照率，所以不可能从光学数据确定其大小。但现在，研究人员根据利用安装在西班牙Pico Veleta的IRAM 30-米射电望远镜获得的热辐射数据已经得到关于该天体大小的一个相当准确的测量数值。该天体直径约3000公里，而冥王星的直径为2000公里。它的反照率与冥王星的差不多，这与其表面为高反射率的富含甲烷的冰层的事实是一致的。
以镧掺杂的锶氧化物为基础的新材料
寻找用在燃料电池阳极中的电化学性质活跃的氧化物的研究工作，一直以低缺陷浓度的材料为重点。这是因为，需要大量能量来使缺陷分散，但这种局限性可能会将一些有重要技术意义的材料排除在外。一种新的研究方法为获得高效的电化学性能提供了另一条途径，该方法是基于对镧掺杂的锶氧化物中缺陷结构的破坏。所获得的新材料在使用中的表现相当不错。这项工作有可能导致能更有效地从化石和碳中性燃料中提取能量的装置问世。
预测疟疾爆发概率的新模型
博茨瓦纳整理了1982–2002年间疟疾发病情况的一个连续记录，为在一个沙漠边缘地区进行疟疾流行病学研究提供了一个独特的数据集。人们知道气候波动在疟疾流行的非洲部分地区是疟疾传播的主要决定因素。现在，根据气候波动与非洲各地疟疾发病率之间已经确立的定量关系，研究人员开发出了一个预测疫情多发区年际气候波动的新系统。这个被称为DEMETER的项目将很多领先的欧洲全球气候预测模型结合在了一起，能够成功预测博茨瓦纳长达5个月时间内爆发疟疾流行的概率，比当前的监测模型发出预警的时间多出4个月，在这4个月的时间内，有关方面可以做出关于资源分配的非常重要的决定来。
大陆地壳的形成过程
大陆地壳形成的速率和这个过程的性质是很有争议的话题。问题的焦点是，如何调和来自火成岩和沉积岩记录的明显矛盾而且不完全的信息。为了帮助解决这种含糊性，Kemp等人利用一系列同位素钟分析了来自冈瓦纳超级大陆的锆石。对同一锆石颗粒上的U-Pb、氧和Lu-Hf同位素所做的顺序测定显示，冈瓦纳超级大陆中的地壳生成是一个不连续的过程，从而对根据从沉积岩中的由放射过程产生的同位素推断出的连续生长观点提出了挑战。
蛇与蜥蜴之间的关系
传统观点认为，在爬行动物中，毒液输送体系只在两个种系中形成：高级蛇类和毒蜥蜴，后者现在以“赫拉毒蜥”（Gila monster）和beaded lizard为代表，它们是被称为Monstersauria的古代的一组捕食性蜥蜴仅存的后代。一项新的研究显示，另外两个主要的蜥蜴种系，即Varanids 和Iguanians，也产生毒素，Iguanian蜥蜴甚至还可能有毒腺。这表明，蛇和蜥蜴之间的关系要比以前所认为的密切得多，蛇是由比较先进的蜥蜴演化来的，而不是由一个单独的演化辐射分支演化来的。
神经细胞的再生问题
成年哺乳动物大脑有显著的再生能力，这个事实使得神经移植干细胞疗法有一天可能成为现实的希望始终没有破灭。然而，新的神经细胞是怎样集成进已有大脑回路的？对这个问题我们很不了解。用小鼠所做的一项新的研究表明，新生神经细胞对已有神经活动是敏感的（通过神经传输物质GABA来感知），这是在活体中这些新的细胞向成年神经回路中集成的关键。（Letter p. 589）干细胞和癌症生物学中一个重要问题是，一个细胞是怎样选择进行增殖或分异的。果蝇卵为研究这个问题提供了一个很好的模型，因为大脑中的成神经细胞在每次细胞分裂时要经历自我更新，产生另一个成神经细胞和一个分异中的子细胞。对一系列果蝇突变体所做的研究表明，成神经细胞更新是由pins、lgl和aPKC基因控制的，这些基因以前被发现调控成神经细胞中的非对称细胞分裂。aPKC的过度表达诱发成神经细胞自我更新，这是一个也许最终会导致控制治疗中所用神经干细胞的方法的研究领域。
造血干细胞所需的一种受体
造血干细胞必须能够在胚胎形成过程中和在骨髓移植后进入骨髓。但Integrins是例外，对这些调控这一过程的分子我们基本不了解。现在，Adams等人发现，这个过程需要一个跨膜钙传感受体。缺少这一受体的造血干细胞能够正常分裂和形成新细胞，但不能往外迁移和进入骨髓。骨髓的高钙含量也许能吸引循环的干细胞，增强向这个小环境中的粘附。这些数据为干细胞的定位和“嫁接”过程确定了一个新的分子参与者，并且提供了一个影响这一过程的潜在目标。
Editorials
When a vaccine is safe p509
Unfounded public fears place pressures on vaccine developers that go beyond reasonable safety considerations, as the search for an acceptable vaccine against Lyme disease may demonstrate.
doi:10.1038/439509a
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Recycling the past p509
The reprocessing of nuclear fuel is an idea that should be laid to rest.
doi:10.1038/439509b
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Malaria quagmire p510
Progress in addressing Africa's largest health problem remains painfully slow.
doi:10.1038/439510a
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Top of pageResearch Highlights
Research highlights p512
doi:10.1038/439512a
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Top of pageNews
Doubts over biochemist's data expose holes in Japanese fraud laws p514
Tokyo university decides that RNA work is not reproducable.
Ichiko Fuyuno and David Cyranoski
doi:10.1038/439514a
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Snapshot: Weather watch p515
Europe's newest satellite sends back colourful view of Earth.
Mark Peplow
doi:10.1038/439515a
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Germany urges NASA to save airborne telescope p515
Fears grow that SOFIA observatory faces the axe.
Tony Reichhard
doi:10.1038/439515b
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Sidelines p516
doi:10.1038/439516a
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Experts plan to reclaim the web for pop science p516
Can peer-reviewed portals strengthen Internet information?
Declan Butler
doi:10.1038/439516b
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Senators seek cash to save US science p517
Republicans and Democrats join forces for more investment.
Geoff Brumfiel
doi:10.1038/439517a
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Stem-cell tagging shows flaws p519
Trusted labelling technique is called into question.
Helen Pearson
doi:10.1038/439519a
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Should journals police scientific fraud? p520
Editors don't expect peer review to catch deliberate fakers. But recent scandals mean that journals are looking at other ways to detect fabricated papers. Emma Marris investigates.
Emma Marris
doi:10.1038/439520a
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Forensic software traces tweaks to images p520
Fraud-busting program hunts for doctored pictures.
Helen Pearson
doi:10.1038/439520b
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News in brief p522
doi:10.1038/439522a
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Correction p522
doi:10.1038/439522b
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Top of pageNews Features
Lyme disease: Uphill Struggle p524
The first vaccine against Lyme disease was withdrawn because patients distrusted it. Should market forces be allowed to shape the next one, asks Alison Abbott.
doi:10.1038/439524a
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Radio astronomy: High and dry p526
Two decades after plans were set in motion for the world's most powerful ground-based telescope, astronomers are bracing themselves for a downgrade to curb escalating costs. Jeff Kanipe reports.
doi:10.1038/439526a
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Endangered species: Time to raise the devil p530
A horrible facial cancer is decimating the Tasmanian devil population. But researchers in Australia think they have found a way to save the species. Carina Dennis reports.
doi:10.1038/439530a
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Top of pageBusiness
Ticking the right boxes p533
Probing parasite's evasive tricks could herald novel anti-inflammatory compounds.
Colin Macilwain
doi:10.1038/439533a
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In brief p533
doi:10.1038/439533b
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Top of pageCorrespondence
Gene-function wiki would let biologists pool worldwide resources p534
Kai Wang
doi:10.1038/439534a
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Conferences that welcome spouses aid research too p534
David A. Shaywitz
doi:10.1038/439534b
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Mudskippers undermine ID claims on macroevolution p534
U. Kutschera
doi:10.1038/439534c
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Reader-appeal should not outweigh merit of research p534
Emilio Artacho
doi:10.1038/439534d
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Top of pageBooks and Arts
A natural history of religion p535
A darwinian philosopher turns his attention to the strength of religion in the United States.
Michael Ruse reviews Breaking the Spell: Religion as a Natural Phenomenon by Daniel C. Dennett
doi:10.1038/439535a
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History by numbers p536
Jeremy Gray reviews God Created the Integers: The Mathematical Breakthroughs that Changed History
doi:10.1038/439536a
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Science in culture: A culture of knowledge p536
An exhibition in Paris explores the golden age of Islamic science.
Pete Jeffs
doi:10.1038/439536b
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Sex and power p537
Tracey Chapman reviews Sexual Conflict by Göran Arnqvist and Locke Rowe
doi:10.1038/439537a
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Top of pageEssay
Concept
The third Bond p539
When James Watson and Francis Crick unveiled their structure of DNA, one of the two kinds of base pair in the molecule was given two hydrogen bonds instead of three. Who spotted the third bond and when?
Simon Wain-Hobson
doi:10.1038/439539a
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Top of pageNews and Views
Solar system: A planet more, a planet less? p541
Further observations of an object dubbed 2003 UB313, which lies beyond Neptune, show that its diameter is around 3,100 kilometres. This makes it larger than Pluto, the smallest 'traditional' Solar System planet.
Scott S. Sheppard
doi:10.1038/439541a
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Molecular biology: Prime-time progress p542
DNA is duplicated within a complex macromolecular machine. Insights into how replication begins and how this is coordinated with progression of DNA synthesis come from a diverse range of sources.
Stephen D. Bell
doi:10.1038/439542a
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Materials Science: Colloids get complex p545
Self-organization of soft-matter components can create complex and beautiful structures. But the intricate structures created by adding a second stage of organization could reveal more than just a pretty face.
Alfons van Blaaderen
doi:10.1038/439545a
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50 & 100 years ago p545
doi:10.1038/439545b
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Neurobiology: Memories of a fruitfly p546
Despite its tiny size, the fruitfly brain is staggeringly intricate. So teasing apart how it remembers things — even a simple line pattern — is a daunting task. Progress is being made, thanks to genetic innovations.
William G. Quinn
doi:10.1038/439546a
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Fluid dynamics: Flows like smoke and honey p547
May Chiao
doi:10.1038/439547a
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Chemistry: Catalysts live and up close p548
Designing efficient solid-state catalysts would be easier if we knew which parts of them do what. Fluorescence microscopy could help: the technique allows single catalytic events to be observed in real time.
Bert M. Weckhuysen
doi:10.1038/439548a
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Top of pageBrief Communications
Allograft theory: Transmission of devil facial-tumour disease p549
An uncanny similarity in the karyotype of these malignant tumours means that they could be infective.
A.-M. Pearse and K. Swift
doi:10.1038/439549a
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Top of pageArticles
Distinct memory traces for two visual features in the Drosophila brain p551
Gang Liu, Holger Seiler, Ai Wen, Troy Zars, Kei Ito, Reinhard Wolf, Martin Heisenberg and Li Liu
doi:10.1038/nature04381
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Replication fork reactivation downstream of a blocked nascent leading strand p557
Ryan C. Heller and Kenneth J. Marians
doi:10.1038/nature04329
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Top of pageLetters
The trans-neptunian object UB313 is larger than Pluto p563
F. Bertoldi, W. Altenhoff, A. Weiss, K.M. Menten and C. Thum
doi:10.1038/nature04494
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A low density of 0.8 g cm-3 for the Trojan binary asteroid 617 Patroclus p565
Franck Marchis, Daniel Hestroffer, Pascal Descamps, Jérôme Berthier, Antonin H. Bouchez, Randall D. Campbell, Jason C. Y. Chin, Marcos A. van Dam, Scott K. Hartman, Erik M. Johansson, Robert E. Lafon, David Le Mignant, Imke de Pater, Paul J. Stomski, Doug M. Summers, Frédéric Vachier, Peter L. Wizinovich and Michael H. Wong
doi:10.1038/nature04350
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Disruption of extended defects in solid oxide fuel cell anodes for methane oxidation p568
Juan Carlos Ruiz-Morales, Jesús Canales-Vázquez, Cristian Savaniu, David Marrero-López, Wuzong Zhou and John T. S. Irvine
doi:10.1038/nature04438
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Spatially resolved observation of crystal-face-dependent catalysis by single turnover counting p572
Maarten B. J. Roeffaers, Bert F. Sels, Hiroshi Uji-i, Frans C. De Schryver, Pierre A. Jacobs, Dirk E. De Vos and Johan Hofkens
doi:10.1038/nature04502
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Malaria early warnings based on seasonal climate forecasts from multi-model ensembles p576
M. C. Thomson, F. J. Doblas-Reyes, S. J. Mason, R. Hagedorn, S. J. Connor, T. Phindela, A. P. Morse and T. N. Palmer
doi:10.1038/nature04503
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Episodic growth of the Gondwana supercontinent from hafnium and oxygen isotopes in zircon p580
A. I. S. Kemp, C. J. Hawkesworth, B. A. Paterson and P. D. Kinny
doi:10.1038/nature04505
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Early evolution of the venom system in lizards and snakes p584
Bryan G. Fry, Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Kim Fung, S. Blair Hedges, Michael K. Richardson, Wayne. C. Hodgson, Vera Ignjatovic, Robyn Summerhayes and Elazar Kochva
doi:10.1038/nature04328
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GABA regulates synaptic integration of newly generated neurons in the adult brain p589
Shaoyu Ge, Eyleen L. K. Goh, Kurt A. Sailor, Yasuji Kitabatake, Guo-li Ming and Hongjun Song
doi:10.1038/nature04404
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Lgl, Pins and aPKC regulate neuroblast self-renewal versus differentiation p594
Cheng-Yu Lee, Kristin J. Robinson and Chris Q. Doe
doi:10.1038/nature04299
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Stem cell engraftment at the endosteal niche is specified by the calcium-sensing receptor p599
Gregor B. Adams, Karissa T. Chabner, Ian R. Alley, Douglas P. Olson, Zbigniew M. Szczepiorkowski, Mark C. Poznansky, Claudine H. Kos, Martin R. Pollak, Edward M. Brown and David T. Scadden
doi:10.1038/nature04247
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Functional genomics reveals genes involved in protein secretion and Golgi organization p604
Frederic Bard, Laetitia Casano, Arrate Mallabiabarrena, Erin Wallace, Kota Saito, Hitoshi Kitayama, Gianni Guizzunti, Yue Hu, Franz Wendler, Ramanuj DasGupta, Norbert Perrimon and Vivek Malhotra
doi:10.1038/nature04377
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Gene network shaping of inherent noise spectra p608
D. W. Austin, M. S. Allen, J. M. McCollum, R. D. Dar, J. R. Wilgus, G. S. Sayler, N. F. Samatova, C. D. Cox and M. L. Simpson
doi:10.1038/nature04194
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Structure of epsilon15 bacteriophage reveals genome organization and DNA packaging/injection apparatus p612
Wen Jiang, Juan Chang, Joanita Jakana, Peter Weigele, Jonathan King and Wah Chiu
doi:10.1038/nature04487
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The mechanism of DNA replication primer synthesis by RNA polymerase p617
Nikolay Zenkin, Tatyana Naryshkina, Konstantin Kuznedelov and Konstantin Severinov
doi:10.1038/nature04337
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DNA primase acts as a molecular brake in DNA replication p621
Jong-Bong Lee, Richard K. Hite, Samir M. Hamdan, X. Sunney Xie, Charles C. Richardson and Antoine M. van Oijen
doi:10.1038/nature04317
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Structure of the cyclic-AMP-responsive exchange factor Epac2 in its auto-inhibited state p625
Holger Rehmann, Joost Das, Puck Knipscheer, Alfred Wittinghofer and Johannes L. Bos
doi:10.1038/nature04468
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Top of pageNaturejobs
Prospect
Stress management p629
Universities take a look at postdocs' mental-health issues
Paul Smaglik
doi:10.1038/nj7076-629a
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Career Views
Ernst Ulrich von Weizsäcker, dean, Donald Bren School of Environmental Science and Management, University of California, Santa Barbara p630
German environmentalist journeys from academia to parliament and back again.
Virginia Gewin
doi:10.1038/nj7076-630a
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Grooming women entrepreneurs p630
Professional organization helps women scientists move from bench to board room.
Robbie Melton
doi:10.1038/nj7076-630b
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A new chapter p630
A watershed year for a former Graduate Journal writer brings fresh career opportunities.
Amber Jenkins
doi:10.1038/nj7076-630c
Full Text | PDF (126K)
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Top of pageFutures
Hiking the roof of the world p632
Just a few simple preparations.
Richard A. Lovett
doi:10.1038/439632a
Full Text | PDF (211K)
