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Nature Contents 3 August 2006 (Vol. 442 pp485-600)
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[自然要览] （选自英国Nature杂志，2006年8月3日出版） 封面故事：一种新型智能液体微型镜头 Adaptive liquid microlenses activated by stimuli-responsive hydrogels 光学成像、医学诊断和“建在一个芯片上的实验室”技术等领域的微型化趋势， 正在为尖端微型镜头创造出一种市场需求。现在，研究人员研制出了一种新型智 能液体微型镜头，它与目前的大多数镜头的不同之处在于，它能自对焦。这种镜 头的关键部件是一种能对刺激产生响应的水溶胶，该水溶胶被集成进一个微型液 体系统中，充当一个液滴的容器。该水溶胶同时探测刺激和促使液滴形状发生变 化，从而也使焦距发生变化。刺激包括生物和化学试剂以及物理参数。在这种微 米尺度上，固定的液-液界面被用来获得稳定的装置，从而实现10秒到几十秒的 响应时间。这样的镜头可以具有几乎任意长度的焦距，并且可以方便地集成进阵 列中。本期封面所示为一种智能液体微型镜头，在其中，一种水溶胶（图中带斑 纹的环）根据一个局部刺激调控镜头形状。（Letter p. 551） 花卉温度对昆虫的吸引力（A warm reception） Behavioural ecology: Bees associate warmth with floral colour 颜色鲜艳的花对授粉的昆虫是有吸引力的，昆虫在飞到这些花上时，会预料到能 获得一种营养回报，如花蜜。但昆虫在选择一种花而不是另一种花时，它们所要 寻找的可能并不只是食物。它们利用大量能量使其体温保持在高于环境温度的水 平上，有些花能提供温暖，用颜色来彰显自己的存在。在一个受控的实验中，大 黄蜂喜欢造访较温暖的花，它们在降落之前利用颜色来预测花的温度。这一发现 对于研究花卉结构的演化可能具有参考价值。（Brief Communication p. 525） P2X受体的重要性（ATP the outsider） P2X receptors as cell-surface ATP sensors in health and disease ATP是所有活细胞中能量交换的通用货币，但它也存在于细胞外，与跨膜受体发 生相互作用，来影响神经细胞、肌肉、腺体和免疫细胞中的细胞内事件。在从细 胞中释放出来时，ATP可激活P2X受体，该受体是存在于大多数身体组织中的非选 择性阳离子通道。由于没有药理学方面的工具，科学家对这些受体所发挥的生理 作用很不了解。但现在有了“苏拉明”(suramin) 和PPADS这样的P2X阻断药物， 这些受体作为细胞表面ATP传感器在健康和疾病中的重要性正在被人们所认识。 （Review Article p. 527） 一些基因对胚胎干细胞分异的影响（A genetic sketch of stem cells） Dissecting self-renewal in stem cells with RNA interference 在一项大规模基因组学研究中，研究人员确定了大量候选基因对细胞分异的调控 作用的贡献。短发卡RNA（shRNA）基因沉寂作用被用来逐个沉寂65个基因的表 达，这些基因的表达水平在小鼠胚胎干细胞分异时是下降的。将这些基因中的7 个删除，会对自我更新产生负面影响。这些分子在使胚胎干细胞具有自我更新的 能力和生成很多其他细胞类型的潜力方面可能发挥着重要作用。（Article p. 533） 通过数值模拟解决标准宇宙模型与观测结果的矛盾（A cosmological paradox） The removal of cusps from galaxy centres by stellar feedback in the early Universe 虽然标准宇宙模型能够成功描述宇宙的大尺度结构，但在较小的尺度上该模型却 不是很好。例如，该模型所预测的附近星系中心暗物质密度（密度曲线中的一个 尖峰或低谷）要比实际观测中所看到的低，这说明星际暗物质晕圈有一个“平 坦”的中心核。Mashchenko等人通过数值模拟解决了这个矛盾。他们的数值模拟 表明，小型原始星系中由以超新星形式出现的恒星反馈作用所驱动的气体的随机 体量运动，有可能使中央暗物质尖峰变平。当这种尖峰被除掉后，在随后的星系 合并过程中将不能再产生，所以在当前的宇宙中，小星系和大星系都会有平坦的 暗物质核心密度曲线。（Letter p. 539） 不会被吞噬的伴星（In the shadow of a giant） Survival of a brown dwarf after engulfment by a red giant star 在像我们的太阳一样的恒星周围的轨道中，已经发现了超过100颗行星和褐矮 星。当这些恒星演变成为红色巨型星时，它们将会轻易吞噬其伴星，而这之后会 发生什么呢？一颗白矮星的第一颗已知的近距离亚恒星（褐矮星）伴星的发现表 明，让我们意想不到的是，这些伴星中有些会在相互作用中存活下来，相对保持 不变。（Letter p. 543; News and Views） 太阳辐射对有机质分解的重要影响（Sunlight drives decay） Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation 生物过程被认为是陆地生态系统中有机质分解的主要原因，而由UV-B辐射所引起 的降解等非生物过程扮演次要角色。但根据在半干旱的巴塔哥尼亚荒原上所进行 的一项研究，事实不是这样的。在这里， 研究发现，影响碳的周转的主要因素 是太阳辐射。阻断全部阳光或UV-B，会大大降低树叶杂草等的分解速度，而土壤 有机物的减少或限制性土壤资源的增加却没有影响。这些结果表明，碳循环有一 个短的周期，初级生产的相当大一部分可能会通过光降解丢失到大气中，而不通 过土壤有机质库进行循环。由于地球陆地表面近40%是沙漠，所以影响辐射水平 的全球变化因素（如臭氧损耗或云层）有可能对碳的存储产生很大影响。 （Letter p. 555） 30亿年前就存在消减过程（Early signs of plate tectonics） Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa Nature杂志上7月13号的一篇News Feature文章透露了关于板块构造“年龄”的 一场争论。板块构造塑造了我们今天所看到的世界，但关于它是什么时候开始的 问题却是一个让地质学家仁者见仁、智者见智的问题。在本期Nature上，Moyen 等人非常可信地论证了在30亿年前就存在消减过程（板块构造的一个关键部 分），而在那时板块构造本身是否存在就曾受到质疑。他们在论证中所依靠的证 据，来自32亿年前一个“太古代”山系（南非的Barberton绿岩带）中高压、低 温变形的标记。这一结果是科学家首次明确指出在“太古代”中期存在这种类型 的活动。（Letter p. 559） 钙调蛋白的水平与鸟喙长度相关（The long and the short of it） The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches 几年前，“达尔文雀类”（指在教科书中始终与自然选择的适应辐射联系在一起 的鸟类）不同物种的喙的深度和厚度被发现与Bmp4 (骨形态遗传蛋白-4)的表达 相关。当时，一次寻找候选目标的筛选工作并没有发现任何有可能与不同喙长度 有关的基因。现在，对不同“达尔文雀类”胚胎的喙原基中的转录情况所做的 DNA微阵列分析表明，钙调蛋白（一种参与Ca2+信号作用的分子）的水平与喙长 度相关。有了这两个调控喙生长不同尺度的通道，就可以设想出一个能够在不同 选择条件下生成很多不同喙结构的机制来，从而也能选择出一个比较好的关于适 应辐射的模型来。（Letter p. 563; News and Views） 面部识别的机制（An eye for a face） Norm-based face encoding by single neurons in the monkey inferotemporal cortex 30年以前，研究人员在猴子的下颞叶皮层中发现了面部选择神经元。尽管此后有 数十项关于这种“面部细胞”的报道，而且人们还普遍假设这样的神经元很可能 参与面部识别，但此后人们几乎没有对尖峰响应与关于人类面部感觉的大量心理 物理文献进行对比。但现在，一组新的实验结果将猴子下颞叶皮层中的面部选择 神经元与关于面部感觉的一个明确的心理层面联系了起来。在该研究中，研究人 员对短尾猴进行训练，让其识别由电脑生成的人脸。结果表明，参加实验的猴子 是通过将电脑生成的一个人脸与其大脑中存储的一个一般的或“标准”的人脸进 行对比来识别的，而不是通过记忆每个人脸是什么样子来进行识别的。人类中的 一个类似的机制也许可解释我们为什么能够在不到一秒的时间内识别出一个面孔 来。（Letter p. 572） 能激活Merlin肿瘤抑制因子的磷酸酶（Tumour-causing cascade） Tumorigenic transformation by CPI-17 through inhibition of a merlin phosphatase 研究人员已经识别出了激活Merlin肿瘤抑制因子（也被称为神经纤维瘤-2）的磷 酸酶。它是一种肌浆球蛋白磷酸酶，被内生抑制因子CPI-17所抑制，后者的水平 在人类肿瘤中经常是升高的，可能通过使Merlin失去活性而有助于癌症的形成。 将这些发现放到一起，我们就会看到一个新的肿瘤抑制级联过程，该过程可通过 至少两种方法被破坏：通过突变（NF2），或通过升高假定的新致癌基因CPI-17 的水平。（Letter p. 576） 描述锯蛋白分异的分析模型（Prions divide then rule） The physical basis of how prion conformations determine strain phenotypes 相同锯蛋白微粒能在活体中产生不同表现型或不同“类别”。这个矛盾通常是用 锯蛋白构型的差异来解释的。Tanaka等人提出了一个分析模型，该模型描述了酵 母中锯蛋白不同物理参数与锯蛋白微粒之间的相互影响何以导致一种特定类型的 锯蛋白的出现。他们的实验显示，最强的表现型事实上是通过一个生长缓慢而脆 性增加（脆性增加会促使锯蛋白分裂）的微粒生成的。 锯蛋白微粒进行分裂、 为进一步生长生成新的“种子”的趋势，在感染性（锯蛋白）和非感染性淀粉质 对其寄主的重大生理影响中可能是一个关键因素。（Letter p. 585） |
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木虫 (正式写手)
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---------------------- NEWS AND VIEWS ---------------------- Evolutionary biology: How to build a longer beak Evolutionary changes in the beaks of Darwin's finches have been instrumental in the adaptive radiation of these birds. The molecular basis for variation in beak size and shape is opening up to investigation. Nipam H. Patel 10.1038/442515a http://www.nature.com/nature/journal/v442/n7102/full/442515a.html 50 & 100 years ago10.1038/442516a http://www.nature.com/nature/journal/v442/n7102/full/442516a.html Particle physics: A finer constant For the first time in a decade, the precision of the fine-structure constant -- central to understanding the electromagnetic force -- has improved. But even greater accuracy is required to test new physics. Andrzej Czarnecki 10.1038/442516b http://www.nature.com/nature/journal/v442/n7102/full/442516b.html Chemical biology: Cutting out the middle manWouldn't it be nice if you could control the function of any protein with one small molecule? Unlikely as it sounds, this could become possible through a crafty process known as protein splicing. Tom W. Muir 10.1038/442517a http://www.nature.com/nature/journal/v442/n7102/full/442517a.html Cell biology: Polarity bites Cells often need to have polarity to function -- cells lining the gut, for instance, secrete digestive enzymes only from their intestinal side. A protein called Bitesize is pivotal in determining which way is up. Richard Fehon 10.1038/nature05036 http://www.nature.com/nature/jou ... ll/nature05036.html Astronomy: A dwarf-eats-dwarf world A white dwarf burnt-out star and a brown dwarf wannabe star have been found in mutual orbit. This fascinating system has had a turbulent past, and its future evolution could be just as spectacular. James Liebert 10.1038/442520a http://www.nature.com/nature/journal/v442/n7102/full/442520a.html Energy technology: Hydrogen quick and clean Systems for producing pure hydrogen for fuel cells from methanol run into problems with energy efficiency and short lifetimes. Unless, that is, you combine the right catalyst and the right purification membrane. Rich Masel 10.1038/442521a http://www.nature.com/nature/journal/v442/n7102/full/442521a.html Superconductivity: Hot vibes Lattice vibrations -- phonons -- have long been implicated in conventional low-temperature superconductivity. That they could also have a supporting role when the heat is turned up had been dismissed. Alex de Lozanne 10.1038/442522a http://www.nature.com/nature/journal/v442/n7102/full/442522a.html ---------------------- BRIEF COMMUNICATIONS ---------------------- Behavioural ecology: Bees associate warmth with floral colour Pollinators may be seeking more than just food as a reward when they choose one flower over another. Adrian G. Dyer et al. 10.1038/442525a Abstract: http://www.nature.com/nature/journal/v442/n7102/abs/442525a. html Article: http://www.nature.com/nature/journal/v442/n7102/full/442525a. html Superhydrophobicity: Drying transition of confined water Long-range hydrophobic interactions operating underwater are important in the mediation of many natural and synthetic phenomena. Seema Singh, Jack Houston, Frank van Swol and C. Jeffrey Brinker 10.1038/442526a Abstract: http://www.nature.com/nature/journal/v442/n7102/abs/442526a. html Article: http://www.nature.com/nature/journal/v442/n7102/full/442526a. html BRIEF COMMUNICATIONS ARISING Glass behaviour: Poisson's ratio and liquid's fragility Spyros N. Yannopoulos and G. P. Johari 10.1038/nature04967 Abstract: http://www.nature.com/nature/jou ... bs/nature04967.html Article: http://www.nature.com/nature/jou ... ll/nature04967.html ---------------------- REVIEW ---------------------- P2X receptors as cell-surface ATP sensors in health and disease Baljit S. Khakh and R. Alan North 10.1038/nature04886 Abstract: http://www.nature.com/nature/jou ... bs/nature04886.html Article: http://www.nature.com/nature/jou ... ll/nature04886.html ---------------------- ARTICLE ---------------------- Dissecting self-renewal in stem cells with RNA interference A large-scale genomic strategy to identify genes that regulate self renewal of mouse embryonic stem cells identified seven genes whose depletion negatively affects self renewal, including four which were not known to have an established role in self renewal. Natalia Ivanova et al. 10.1038/nature04915 Abstract: http://www.nature.com/nature/jou ... bs/nature04915.html Article: http://www.nature.com/nature/jou ... ll/nature04915.html ---------------------- LETTERS ---------------------- The removal of cusps from galaxy centres by stellar feedback in the early Universe Numerical simulations show that random bulk motions of gas in small primordial galaxies, driven by stellar feedback in the form of supernovae, will result in a flattening of the central dark matter cusp on short timescales. Once removed, the cusp cannot be reintroduced during the subsequent mergers involved in the build-up of larger galaxies. Sergey Mashchenko, H. M. P. Couchman and James Wadsley 10.1038/nature04944 Abstract: http://www.nature.com/nature/jou ... bs/nature04944.html Article: http://www.nature.com/nature/jou ... ll/nature04944.html Survival of a brown dwarf after engulfment by a red giant star Many sub-stellar companions orbit solar-type stars. These stars can engulf their companions when they become red giants. This paper reports the discovery of a brown dwarf in a short-period orbit around a white dwarf, where the engulfment of the brown dwarf had little effect on it. P. F. L. Maxted, R. Napiwotzki, P. D. Dobbie and M. R. Burleigh 10.1038/nature04987 Abstract: http://www.nature.com/nature/jou ... bs/nature04987.html Article: http://www.nature.com/nature/jou ... ll/nature04987.html Interplay of electron-lattice interactions and superconductivity in Bi2Sr2CaCu2O8+δ Jinho Lee et al. 10.1038/nature04973 Abstract: http://www.nature.com/nature/jou ... bs/nature04973.html Article: http://www.nature.com/nature/jou ... ll/nature04973.html Adaptive liquid microlenses activated by stimuli-responsive hydrogels Liang Dong, Abhishek K. Agarwal, David J. Beebe and Hongrui Jiang 10.1038/nature05024 Abstract: http://www.nature.com/nature/jou ... bs/nature05024.html Article: http://www.nature.com/nature/jou ... ll/nature05024.html Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation Solar radiation is a dominant control on the rate of leaf litter decomposition in the semi-arid Patagonian steppe, which suggests that factors such as cloud cover may influence carbon cycling in semi-arid environments. Amy T. Austin and Lucia Vivanco 10.1038/nature05038 Abstract: http://www.nature.com/nature/jou ... bs/nature05038.html Article: http://www.nature.com/nature/jou ... ll/nature05038.html Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa Jean-Francois Moyen, Gary Stevens and Alexander Kisters 10.1038/nature04972 Abstract: http://www.nature.com/nature/jou ... bs/nature04972.html Article: http://www.nature.com/nature/jou ... ll/nature04972.html The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches Arhat Abzhanov et al. 10.1038/nature04843 Abstract: http://www.nature.com/nature/jou ... bs/nature04843.html Article: http://www.nature.com/nature/jou ... ll/nature04843.html Collinear activation of Hoxb genes during gastrulation is linked to mesoderm cell ingression Hox genes are first activated in precursor cells of somites, where they control the migratory properties of these cells, and the timing of their ingression and final position in the developing vertebrate column. Tadahiro Iimura and Olivier Pourquie 10.1038/nature04838 Abstract: http://www.nature.com/nature/jou ... bs/nature04838.html Article: http://www.nature.com/nature/jou ... ll/nature04838.html Norm-based face encoding by single neurons in the monkey inferotemporal cortex By varying the information present in faces using morphing software, face-responsive neurons were shown to be highly sensitive to very small differences in the amount of identity present in a face, consistent with the idea that face-selective responses in this brain area reflect a comparison between an incoming face and an internal reference or norm. David A. Leopold, Igor V. Bondar and Martin A. Giese 10.1038/nature04951 Abstract: http://www.nature.com/nature/jou ... bs/nature04951.html Article: http://www.nature.com/nature/jou ... ll/nature04951.html Tumorigenic transformation by CPI-17 through inhibition of a merlin phosphatase A phosphatase that activates the tumour suppressor protein merlin is identified. An endogenous inhibitor of this phosphatase is often upregulated in human tumours and may contribute to the development of cancer by inactivating merlin. Hongchuan Jin, Tobias Sperka, Peter Herrlich and Helen Morrison 10.1038/nature04856 Abstract: http://www.nature.com/nature/jou ... bs/nature04856.html Article: http://www.nature.com/nature/jou ... ll/nature04856.html Spatial control of actin organization at adherens junctions by a synaptotagmin-like protein Btsz The synaptotagmin-like protein Bitesize spatially controls F-actin at adherens junctions of the Drosophila primary embryonic epithelium independent of E-cadherin. The polarity cues Par-3 and Phosphatidylinositol (4,5)-biphosphate localize Bitesize in the junctional area. Bitesize binds the F-actin-binding protein Moesin, and thereby controls junction stability. Fanny Pilot, Jean-Marc Philippe, Celine Lemmers and Thomas Lecuit 10.1038/nature04935 Abstract: http://www.nature.com/nature/jou ... bs/nature04935.html Article: http://www.nature.com/nature/jou ... ll/nature04935.html The physical basis of how prion conformations determine strain phenotypes An analytical model describes how the interplay of various physical parameters of prions and prion particles in yeast leads to the emergence of a particular prion strain. The ability of prion particles to divide and generate new seeds for further growth turns out to be a key determinant of their physiological impact. Motomasa Tanaka, Sean R. Collins, Brandon H. Toyama and Jonathan S. Weissman 10.1038/nature04922 Abstract: http://www.nature.com/nature/jou ... bs/nature04922.html Article: http://www.nature.com/nature/jou ... ll/nature04922.html Rad54 protein promotes branch migration of Holliday junctions Rad54, a translocase that uses the energy of ATP hydrolysis to move along a duplex, promotes Holliday junction branch migration. Genetic studies in yeast have implicated Rad54 as acting late in recombination, when Holliday junctions are present. Dmitry V. Bugreev, Olga M. Mazina and Alexander V. Mazin 10.1038/nature04889 Abstract: http://www.nature.com/nature/jou ... bs/nature04889.html Article: http://www.nature.com/nature/jou ... ll/nature04889.html |
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