2007年11月15日Nature中文摘要

封面故事：气候问题成为美澳大选中的重要问题
本期Nature杂志刊登一组关于气候变化在澳大利亚和美国的政治影响的News
Features文章。在澳大利亚，全球变暖正在成为11月24日大选中的一个重要竞选
问题。拒绝签署关于气候变化的《京都议定书》的现任总理霍华德在民意测验中
落后于竞选对手、劳动党的Kevin Rudd，后者已经表示，如果他当选，他将批准
《京都议定书》。观察家把气候问题作为二者之间的一个决定性问题。澳大利亚
目前正在发生的旱灾也许会继续促使选民比过去更多地去思考气候问题。在美
国，总统竞选正在大张旗鼓地进行，虽然大选还有整整一年时间。领先的总统候
选人都已发表了关于支持气候变化行动的不同程度的声明。但新总统在2009年1
月就职后有什么样的权力来实行真正的变化呢？Nature杂志对美国总统所扮演的
角色及在权力过渡之后预计会发生什么进行了分析。本期Nature还发表了工业界
人士、立法专家和政策专家对当前正在美国国会进行的气候立法工作的看法，以
及我们的专栏作者、政策专家David Goldston对最终可能形成的法律所做的预
测。
（News Features）

“军团病”病原体致病能力的分子机制（Living in a vacuole）
Legionella pneumophila proteins that regulate Rab1 membrane cycling
使得最常见的“军团病”（Legionnaire’s disease）病原体毒性如此之强的特
性之一，是其能够在宿主的巨噬細胞消化该细菌时“劫持”在巨噬細胞内所形成
的液泡的能力。这种液泡本来是宿主的酶消灭该病原体的地方，但该病原体能够
“劫持”这种液泡，并引导其被输送到内质网上，在那里细菌可以繁殖。现在，
这一过程中所涉及的两种细菌蛋白已经被识别出来。DrrA蛋白能够打开一个分子
开关Rab1，破坏其功能，以便让内质网和液泡融合。然后，当细菌已经安全地
进入内质网时，LepB就可以通过将Rab1开关关掉来掩盖该病原体的踪迹。
（Article p. 365; News & Views）

离子通道在膜电压作用下被打开的分子机制（Channels with potential）
Portability of paddle motif function and pharmacology in voltage
sensors / Atomic structure of a voltage-dependent K+ channel in a
lipid membrane-like environment
依赖于电压的离子通道响应于膜电压的变化而打开，但发生这一过程的分子机制
却不清楚。由MacKinnon 及其同事在2003年所做的先驱性工作表明，该过程涉及
一种类脂暴露的“桨”状结构的运动，但这种运动的性质仍然存在争议。在两篇
互补性文章的第一篇中，Alabi等人通过证明这种“桨”状结构的功能在移植进
关系较远的通道中时被忠实保留下来的事实说明了这种结构特征的重要性。这项
工作还强调了膜内这一结构的移动性。 Long等人描述了被由类脂排列成的一个
类似于双层的体系所包围的一个被改变了的Kv1.2钾通道的高分辨率结构。
“桨”状结构中的临界正电荷被类脂和蛋白相互作用所稳定，这说明了该“桨”
状结构可能会以某种方式响应于电压的变化而运动，将该通道孔打开。
（Articles pp. 370, 376）

人β2AR肾上腺素受体的晶体结构（A tough structure to crack）
Crystal structure of the human 2 adrenergic G-protein-coupled
receptor
大多数荷尔蒙和神经传递物质（因此也包括很多药物）通过G-蛋白耦合的受体
（被称为GPCRs）发生作用。除了Rhodopsin（已知最稳定的GPCR）是个例外之
外，这些蛋白的结构数据都难以获得。现在，在本期Nature杂志上同时也在
Science杂志上发表了论文的几个合作研究小组利用大量不同方法，包括利用反
向激动剂Carazolol来稳定该受体结构的方法，对人β2AR肾上腺素受体的晶体结
构进行了测定。其结构与“暗”Rhodopsin的结构形成鲜明对比，这可以帮助解
释为什么制备大多数GPCRs的达到衍射质量的晶体是如此困难。
（Article p. 383; News & Views）

最亮超新星诞生于恒星碰撞（Collision course）
A runaway collision in a young star cluster as the origin of the
brightest supernova / Pulsational pair instability as an explanation
for the most luminous supernovae
SN 2006gy是一次极为明亮的超新星爆炸，也许比从一个巨型恒星核心坍缩所形
成的一颗典型的超新星能量高100倍。目前的理论认为，它的前身是一颗质量是
太阳100倍的恒星。这种结论与该超新星的光谱是相矛盾的，其光谱表明存在一
个氢包裹层，这种包裹层对一颗巨型恒星来说早在爆炸之前就失去了。现在，两
个研究小组提出了支持对该超新星做出其他解释的证据，它们都涉及到碰撞。
Simon Portegies Zwart 和 Edward van den Heuvel发现，在一个致密的年轻星
团中巨型恒星的碰撞频率足以说明SN 2006gy是有可能从这种大碰撞中形成的。
Woosley等人提出了一个模型，该模型将这一最亮的超新星解释为由巨型恒星喷
射出的物质壳之间所发生的碰撞的产物，这些巨型恒星因为电子-正电子对的产
生而变得不稳定。
（Letters pp. 388, 390）

受海森堡测不准原理限制的极限测量精度已达到（Heisenberg’s the limit）
Entanglement-free Heisenberg-limited phase estimation
在基础层面上，测量精度受限于所涉及的量子资源（如光子）的数量，而标准相
测量方案导致一种不确定性（标准量子极限），该不确定性与这一数量成比例关
系。理论上，应当有可能达到仅仅受限于海森堡测不准原理的一个精度。有少量
实验已经打破了标准量子极限，但此前没有一个达到海森堡极限，主要是由于需
要难以生成的奇异的量子纠缠状态。Higgins等人采用了另一种方法，该方法利
用了没有纠缠的光子状态，允许它们实现受海森堡测不准原理限制的相。这标志
着为实现量子增强的测量精度而进行的工作的复杂性有了极大降低。
（Letter p. 393; News & Views）

一种关于超材料的理论架构（Rainbow’s end）
'Trapped rainbow' storage of light in metamaterials
被称为超材料（Metamaterials）的含有具有各种不同形状和排列的金属包容物
的透明材料，能使光以不寻常的方式传播。Tsakmakidis等人介绍了一种关于超
材料的理论架构，该架构能使光完全静止。与以前对光进行减速和储存的方法相
比，这一新方法能够实现高耦合效率，同时允许宽带室温操作。在达到一个临界
点时，光线就无法进一步传播；由于光波的每个频率成分（或颜色）是在稍微不
同的地方被阻止的，所以这将导致一个“被束缚的彩虹”的形成。这项工作在两
个重要的现代科学领域——超材料和慢光（slow light）——之间架起了桥梁，
并且还有可能导致在光数据处理和存储方面或在量子光学记忆装置的实现方面的
应用。
（Letter p. 397）

细菌之间的信号欺骗（Communication cheats）
Cooperation and conflict in quorum-sensing bacterial populations
细菌之间通过小型可扩散分子的释放和感应（或群体感应）来进行的通信，被认
为是在种群层面上协调合作行为的一种方式。演化理论预测，彼此进行沟通和合
作的个体还能被骗子所利用，后者要么不发出信号，要么不对信号做出反应。现
在，对病原体绿脓杆菌（Pseudomonas aeruginosa）（它们在细胞之间通过信号
进行联系来调控毒性因子表达）的种群所做的实验证实，信号和信号受体突变体
（或称“欺骗信号”）的确都有一个适应优势。但对欺骗问题的解决办法的确以
亲缘选择的形式而存在——近亲之间倾向于进行“诚实的”沟通。这些发现为在
人体细菌感染中所观测到的欺骗信号的传播提供了一个解释。
（Letter p. 411）

Hcrt神经元的光刺激研究（Sleepers awake）
Neural substrates of awakening probed with optogenetic control of
hypocretin neurons
4月份Nature杂志上发表的一篇论文提出这样一个有趣的可能性：也许可以开发
光疗法来治疗神经疾病。这项用组织切片和和线虫所进行的研究工作表明，可以
通过遗传工程方法来处理脑细胞，以改变它们对不同颜色光脉冲做出反应的活
性。现在，一项跟踪研究表明，用类似方法可以改变一个活的哺乳动物的行为。
下视丘（Hypothalamus）中能够产生下视丘分泌素（Hypocretin）的神经元（称
之为Hcrt神经元）在从睡眠向清醒过渡的过程中是活跃的。通过遗传工程方法对
小鼠的Hcrt神经元进行处理，使其能够对光做出反应，然后用光对其进行刺激，
可以增加从睡眠向清醒过渡的可能性，更高的频率能造成更突然的唤醒。由于
Hcrt缺乏与嗜睡症有关，所以这些结果也许可为了解睡眠失调提供线索。
（Letter p. 420）

“凋亡”细胞信号的辨识及其受体（Apototic cells on the menu）
BAI1 is an engulfment receptor for apoptotic cells upstream of the
ELMO/Dock180/Rac module / Identification of Tim4 as a
phosphatidylserine receptor
在多细胞生物的细胞程序死亡过程中，大量细胞被巨噬细胞吞噬，从而避免正在
死去的细胞释放有毒物质。这些“凋亡”细胞将它们表面上的“磷脂酰丝氨酸”
（PS）作为一种“来吃我吧”信号暴露出来。Miyanishi等人发现，受体Tim4 和
Tim1与吞噬细胞对PS的识别有关，而Park等人则发现，BAI1蛋白是哺乳动物巨噬
细胞中PS的一个受体。
（Letters pp. 430, 435）

RNA聚合酶-II还能以RNA为模板（NEW TRICKS）
Molecular basis of RNA-dependent RNA polymerase II activity
RNA聚合酶-II（一种负责基因表达过程中的第一步——转录的酶）过去被认为只
用DNA作为模板。但是现在人们发现，RNA聚合酶-II还能从一个RNA模板产生互补
性RNA产物。真核细胞中一个中心成分的这一新发现的活性很可能与基于小RNA分
子的基因调控机制有关。（Letter p. 445）

----------------------
NEWS AND VIEWS
----------------------
Structural biology: A receptor unlocked pp355 - 356
G-protein-coupled receptors govern many biological functions, yet
little is known about the molecular basis of their activity. The
structure of a prominent example of these receptors is now revealed.
Stephen R. Sprang
doi:10.1038/450355a
http://www.nature.com/nature/journal/v450/n7168/full/450355a.html

Planetary science: Isotopic lunacy pp356 - 357
The Moon could have been derived from a well-mixed disk of rock vapour
that was produced after the early Earth collided with another planet.
This persuasive idea offers a fresh perspective on the history of both
bodies.
Alex N. Halliday
doi:10.1038/450356a
http://www.nature.com/nature/journal/v450/n7168/full/450356a.html

Epigenetics: Reversing the 'irreversible' pp357 - 359
"Do not speak ― unless it improves on silence" is generally wise
advice, and is even vital for a subset of essential genes. New studies
describe how, when appropriate, the silence of these genes is broken.
Richard S. Jones
doi:10.1038/450357a
http://www.nature.com/nature/journal/v450/n7168/full/450357a.html

Carbon cycle: Quick burial at sea pp360 - 361
The amount of river-borne carbon that is buried upon reaching the sea
affects Earth's atmospheric composition. A study of rivers draining
the Himalaya shows that carbon burial may occur more efficiently than
was thought.
Caroline A. Masiello
doi:10.1038/450360a
http://www.nature.com/nature/journal/v450/n7168/full/450360a.html

Microbiology: Pathogen drop-kick pp361 - 362
To set the scene for its replication, the bacterium Legionella
pneumophila exploits its host cells' Rab1 protein. This pathogen seems
to use minimal resources to mimic the normal cycle of Rab1 activity.
Suzanne Pfeffer
doi:10.1038/450361a
http://www.nature.com/nature/journal/v450/n7168/full/450361a.html

50 & 100 Years Ago p362
doi:10.1038/450362a
http://www.nature.com/nature/journal/v450/n7168/full/450362a.html

Quantum optics: Kittens catch phase pp362 - 363
The most sensitive phase-measuring instrument yet uses quantum
trickery and a scaled-down version of the notorious Schroedinger's
cat. It means that more sensitive devices for metrology and imaging
could be on the way.
Jonathan P. Dowling
doi:10.1038/450362b
http://www.nature.com/nature/journal/v450/n7168/full/450362b.html

Clarification p363
doi:10.1038/450363a
http://www.nature.com/nature/journal/v450/n7168/full/450363a.html

----------------------
ARTICLES
----------------------
Portability of paddle motif function and pharmacology in voltage
sensors pp370 - 375
One of two papers that demonstrates the importance of the
lipid-exposed 'paddle' motif in voltage-dependant ion channels by
showing that paddle function can be faithfully conserved when
transplanted into distantly-related channels. The work also
underscores the mobility of this motif within the membrane.
AbdulRasheed A. Alabi et al.
doi:10.1038/nature06266
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06266.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06266.html

Atomic structure of a voltage-dependent K+ channel in a lipid
membrane-like environment pp376 - 382
The second of two papers about the mechanism of voltage-activation of
ion channels describes a high resolution structure of a modified Kv1.2
potassium channel surrounded by a bilayer-like arrangement of lipids.
The work reveals how critical positive charges in the paddle are
stabilized by both lipid and protein interactions and suggests a way
in which the paddle may move in response to voltage to open the
channel pore.
Stephen B. Long, Xiao Tao, Ernest B. Campbell and Roderick MacKinnon
doi:10.1038/nature06265
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06265.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06265.html

----------------------
LETTERS
----------------------
A runaway collision in a young star cluster as the origin of the
brightest supernova pp388 - 389
Supernova 2006gy in the galaxy NGC 1260 is the most luminous one
recorded. Its progenitor might have been a very massive star, but that
is incompatible with hydrogen in the spectrum of the supernova.
Instead, it might have arisen from the merger of two massive stars.
However, the collision frequency of massive stars in a dense and young
cluster is sufficient to provide a reasonable chance that SN 2006gy
resulted from such a bombardment.
Simon F. Portegies Zwart and Edward P. J. van den Heuvel
doi:10.1038/nature06276
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06276.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06276.html

Pulsational pair instability as an explanation for the most luminous
supernovae pp390 - 392
This paper reports that the brightest supernovae arise from collisions
between shells of matter ejected by massive stars. An
electron-positron 'pair instability' leads to explosive burning that
ejects many solar masses of material. When the next explosion occurs,
several solar masses of material are again ejected, which collide with
the earlier ejecta, radiating 1050 erg of light.
S. E. Woosley, S. Blinnikov and Alexander Heger
doi:10.1038/nature06333
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06333.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06333.html

Entanglement-free Heisenberg-limited phase estimation pp393 - 396
At the fundamental level, measurement precision is limited by the
number of quantum resources that are used. Standard measurement
schemes lead to a phase uncertainty that scales with this number. In
principle, it should be possible to achieve a precision limited only
by the Heisenberg uncertainty principle. Here, an approach using
unentangled single-photon states enables the achievement of
Heisenberg-limited phase estimation. This represents a drastic
reduction in the complexity of achieving quantum-enhanced measurement
precision.
B. L. Higgins et al.
doi:10.1038/nature06257
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06257.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06257.html

'Trapped rainbow' storage of light in metamaterials pp397 - 401
Kosmas L. Tsakmakidis, Allan D. Boardman and Ortwin Hess
doi:10.1038/nature06285
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06285.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06285.html

Generation of single optical plasmons in metallic nanowires coupled to
quantum dots pp402 - 406
A new approach for achieving strong coupling between optical emitters
and their environment is demonstrated by combining techniques and
ideas from plasmon and quantum optics. The emitter is a semiconductor
quantum dot that is placed near a silver nanowire. Light from the
quantum dot can couple directly to guided surface plasmons inside the
metallic nanowire, which causes the ends of the nanowire to light up.
Spectroscopy measurements indicate that this is the result of single
plasmons scattering from the wire end.
A. V. Akimov et al.
doi:10.1038/nature06230
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06230.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06230.html

Efficient organic carbon burial in the Bengal fan sustained by the
Himalayan erosional system pp407 - 410
A comprehensive organic carbon budget for the Himalayan erosional
system is presented, and finds that organic carbon export is
controlled by sediment properties and that oxidative loss is
negligible during transport and deposition to the ocean. The results
indicate that 70 to 85 per cent of the organic carbon is recent
organic matter captured during transport, which serves as a net sink
for atmospheric carbon dioxide.
Valier Galy et al.
doi:10.1038/nature06273
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06273.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06273.html

Cooperation and conflict in quorum-sensing bacterial
populations pp411 - 414
Several bacterial pathogens including Pseudomonas aeruginosa use
cell-to-cell signalling to regulate virulence factor expression. The
cost of communication is believed to allow for cheaters and this paper
provides experimental evidence that this is the case, signal and
signal-receptor mutants display a fitness advantage. But this
advantage decreases with an increase in relatedness of the competing
strains, a phenomenon known as kin selection.
Stephen P. Diggle, Ashleigh S. Griffin, Genevieve S. Campbell and
Stuart A. West
doi:10.1038/nature06279
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06279.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06279.html

A synaptic memory trace for cortical receptive field plasticity pp425
- 429
Robert C. Froemke, Michael M. Merzenich and Christoph E. Schreiner
doi:10.1038/nature06289
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06289.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06289.html

BAI1 is an engulfment receptor for apoptotic cells upstream of the
ELMO/Dock180/Rac module pp430 - 434
Apoptotic cells must be removed by phagocytes to avoid local
inflammation. They expose phosphatidylserine, which is normally
restricted to the inner leaflet of the plasma membrane, on their
surface, acting as an 'eat-me' signal. This paper shows that the BAI1
protein is an upstream receptor for phosphatidylserine in mammalian
macrophages
Daeho Park et al.
doi:10.1038/nature06329
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06329.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06329.html

SIRT1 regulates the histone methyl-transferase SUV39H1 during
heterochromatin formation pp440 - 444
SUV39H1 is the major methyltransferase responsible for tri-methylation
of histone H3 at lysine 9 in heterochromatin. The histone deacetylase
SIRT1 is shown to target the SUV39H1 enzyme and contribute to elevated
levels of SUV39H1 activity and H3K9me3 in heterochromatin.
Alejandro Vaquero et al.
doi:10.1038/nature06268
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06268.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06268.html

Molecular basis of RNA-dependent RNA polymerase II activity pp445
- 449
RNA polymerase II (Pol II) uses a DNA template to direct RNA synthesis
during transcription, but there is also emerging evidence that it can
use RNA as a template. In this paper the RNA-dependent RNA polymerase
activity of Pol II is biochemically and structurally characterized.
Elisabeth Lehmann, Florian Brueckner and Patrick Cramer
doi:10.1038/nature06290
Abstract:
http://www.nature.com/nature/journal/v450/n7168/abs/nature06290.html
Article:
http://www.nature.com/nature/journal/v450/n7168/full/nature06290.html

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2007年11月15日Nature中文摘要