（选自英国Nature杂志，2007年3月8日出版）
封面故事：格陵兰冰川的历史
Continental ice in Greenland during the Eocene and Oligocene
本期封面所示为2006年由南安普顿大学的Simon A. Johnson拍摄的一个格陵兰冰
排（ice raft）。从始新世到渐新世的过渡（距今大约3350万年前）时期，全球
气候发生了一次重大变化，从没有大冰层变化为有一个永久性的南极冰层，大小
跟今天的南极冰层差不多。然而，关于北半球早期冰川史的性质却很有争议。本
期Nature上一篇论文，报告了来自挪威-格陵兰海的晚始新世至早渐新世沉积层
中的从地层学来说范围很大的冰排碎片，是在距今3800万年至3000万年前沉积
的。这表明，格陵兰冰川的存在要比以前所记录的早2000万年。（Letter p.
176）“国际极地年2007-2008”本月开始，Nature杂志将通过报道即将进行的钻
探项目以及关于未来北极变暖最新预测的系列News Features文章，来配合“国
际极地年”活动。（Editorials p. 109; News Features）
19世纪早期德国的音乐史（MOOD MUSIC）
A scientific symphony
在其Harmonious Triads一书中，历史学家和大提琴演奏家Myles Jackson为我们
描述了19世纪早期德国历史中一个引人注目的时期。当时，音乐、科学和技术综
合起来，产生了新的乐器、新的音乐表演形式和新的思维方式。并非所有乐器都
经受住了时间的检验，但这一极度活跃的时期所产生的影响在19世纪末德国的科
学、文化和政治中都能找到踪迹。（Books & Arts p.140）
与癌症有关的突变（Cancer gene haul）
Patterns of somatic mutation in human cancer genomes
通过扫描定位（mapping）、生物鉴定（bioassay）等成熟方法以及通过识别可
信的生物学候选目标，已经识别出了超过350个致癌基因。现在，人类基因组序
列的确定意味着，大规模测序研究能够进一步发现很多候选致癌基因。蛋白激酶
是很多调控过程的关键，它们功能的丧失是肿瘤的一个常见的诱因。所以，研究
人员选择了一批与超过200种癌症相关的528个激酶，来进行一个大型测序研究工
作。该研究显示了超过1000个以前不知道的突变，它们以某种方式与肿瘤的形成
有关：其中有些是所谓的“乘客”突变，即不参与癌症形成；但其中超过100个
是所谓的“司机”突变，它们参与癌症形成。这种类型的基因家族研究，能发现
导致癌症的缺陷，也能发现分子诊断和治疗的新目标。（Article p. 153; News
& Views）
矮新星与经典新星之间的联系找到观测依据（The bright and distant past）
An ancient nova shell around the dwarf nova Z Camelopardalis
矮新星是一种激变变星(cataclysmic variables)，它包含一个坍缩的白矮星，
后者从其在一个双星体系中的伴星（一个红矮星）获得物质而不断增长。一种不
稳定因素周期性地将物质倾倒到这个白矮星上，使其发光度增加100倍。经典的
新星要比矮新星亮数千倍，同时伴随着该体系周围壳层的形成。理论预测，矮新
星最终将获得足够多的质量，从而经历经典的新星爆发。现在，矮新星与经典新
星之间这一被怀疑存在的联系，随着在矮新星Z Camelopardalis（简称Z Cam）
周围一个古老新星壳层的发现，已经有了一个观测结果作为依据。该壳层的性质
表明，几千年前，Z Cam经历了一次经典的新星爆发，并且在若干天里它是天空
中最明亮的星星之一。（Letter p. 159）
火星Meridiani地区蒸发岩的形成机制（Martian water goes global）
Meridiani Planum and the global hydrology of Mars
由“机遇者”漫游车所勘察的火星Meridiani Planum地区的蒸发岩沉积物，被解
释为存在一个波动的地下水位的证据。但这种解释有一个问题：这个地区首先没
有盆地地形来解释蒸发岩的存在。一个新的水文学模拟研究绕开了这一困难，因
为研究人员提出了一个机制，按照这个机制，蒸发岩是有可能在Meridiani地区
形成的，而不需要在一个封闭的盆地中积聚水，原因是火星全球地下水在不断上
涌和蒸发。（Letter p. 163）
双通道Kondo效应已被观测到（It takes two to Kondo）
Observation of the two-channel Kondo effect
半导体量子点（紧紧束缚电子运动的纳米结构）已成为研究和操纵一个或几个电
子行为的有用的模型体系。被研究得最彻底的现象之一是Kondo效应，即一个量
子点上的一个孤立的电子自旋与电极中的大量电子发生强烈相互作用，产生一种
复杂的多粒子状态。一个有微妙不同的、但观测起来却要困难得多的现象是双通
道Kondo效应，即两个电极中的电子通过它们与局限在一个量子点中的单独一个
自旋之间的相互作用纠缠在一起。与传统Kondo效应不同的是，这一新效应无法
在关于费米液体的电子行为的传统画面中来描述。现在，科学家苦苦追寻的双通
道Kondo效应已在量子点中被观测到，而该效应首次被预测到已是25年前的事情
了。该体系可在显微尺度上实现精确控制，所以这一成果可以被看作是朝着实现
根据需要来设计半导体纳米结构的方向迈出的一步。（Letter p. 167）
还原二氧化硅的一种低温方法（Silicon in good shape）
Chemical reduction of three-dimensional silica micro-assemblies into
microporous silicon replicas
将二氧化硅（SiO2）还原成硅（Si）的一种低温方法，有可能为以前仅仅被看作
是绝缘氧化物的微型结构找到很多新用途，如硅藻的微型壳和定制的自组装结构
等。该方法在650 °C将二氧化硅转换成硅，而要求将硅熔化的方法却需要在
2,000 °C左右才能做到。该方法还能保留原始二氧化硅的架构，并在产生的硅
中复制这种架构，正如图中所示的14纳米长的这个样本一样。像这样的硅结构有
可能用作传感器，以及用在电子、光学和生物医学等领域。（Letter p. 172;
News & Views）
动物能飞是因基因组变小（Chicken and genome question）
Origin of avian genome size and structure in non-avian dinosaurs
与脊椎动物飞行有关的、人们不是很了解的因素之一是基因组大小的减小。鸟类
与脊椎动物相比基因组小得多，蝙蝠一般比不会飞的脊椎动物基因组要小。但
是，是飞行使得基因组变小的、还是基因组变小才使得动物能够飞行的？根据对
恐龙骨细胞体积和基因组大小所做的广泛分析来判断，事实似乎是后一种情况。
基因组减小可以追溯到蜥臀目恐龙（在这一类恐龙中鸟类是惟一现存的成员），
但在鸟臀目恐龙中却没有。所以，基因组减小就可以归到我们现在跟鸟类联系在
一起的一组形态特征中，这些形态特征可以远远追溯到鸟类的恐龙祖先。
（Letter p. 180）
关于皮肤更新机制的新模型（Skin renewal）
A single type of progenitor cell maintains normal epidermis
30多年来，被人们所接受的表皮动态平衡模型一直假设，皮肤组织是由两组单独
的先祖细胞来维持的。过去，自更新干细胞被认为产生短寿命的先祖细胞，后者
又形成新的表皮。Clayton等人现在提出，这一假设可被一个更简单的模型代
替，按照这个更简单的模型，仅一种类型的先祖细胞发生非对称分裂，其分裂速
度可确保表皮动态平衡。（Letter p. 185）
大脑确定方位的方式和机制（A sense of place）
Hippocampal remapping and grid realignment in entorhinal cortex
人们的定位能力取决于大脑对关于位置、方向和距离的信息的综合能力。最近的
研究成果表明，大脑“嗅内野皮質”（entorhinal cortex）中的“网格细胞”
（grid cells）是大脑计算位置的机制的一个构成部分，但科学家对负责空间导
航和空间记忆形成的神经网络计算却不了解。现在，让大鼠在变化的环境中寻找
食物来源的实验显示，海马体中记忆的表示有两个截然不同的代码。海马体地点
细胞中在统计上独立的表示方式的形成（“重新定位”过程），总是在“嗅内野
皮質”中相应的全部定位图的一致的迁移之后进行。这将使一个动物的位置能够
被其遇到不同环境时的同一翻译机制来表示和更新。（Letter p. 190）
表皮组织被确定是决定植物根生长的关键（The third way）
The epidermis both drives and restricts plant shoot growth
植物根由三个组织类型形成—表皮组织、表皮下组织和内层细胞组织。其中的一
个类型是决定植物最终大小的关键，但到底是哪一种，一个多世纪以来一直有争
议。现在，矮拟南芥植物中油菜素内酯(brassinosteroid)生物合成基因的定向
表达实验为这个问题提供了答案：是表皮组织既促进根的生长又限制根的生长。
油菜素内酯是在化学性质上与“可的松”（cortisol）有关的植物激素，对植物
生长有广谱效应。（Letter p. 199; News & Views）
----------------------
NEWS AND VIEWS
----------------------
Cancer: Drivers and passengers pp145 - 146
Studies that have provided the first unbiased, large-scale analyses of
DNA mutations across an array of cancers also have lessons for the
proposal to annotate the entire cancer genome.
Daniel A. Haber and Jeff Settleman
10.1038/446145a
http://www.nature.com/nature/journal/v446/n7132/full/446145a.html
Materials science: Silicon life forms pp146 - 147
A simple chemical reduction process has been used to replicate
intricate natural networks of silica at a relatively low temperature.
The equally elaborate product is made of silicon ― electronics'
golden boy.
David J. Norris
10.1038/446146a
http://www.nature.com/nature/journal/v446/n7132/full/446146a.html
Evolutionary biology: The Elvis paradox pp147 - 149
Evidence for a universal driver of evolution across all timescales
could mean that the venerable paradox of stasis is dead. But even with
such evidence, some biologists would be reluctant to accept its
passing.
Andrew Hendry
10.1038/446147a
http://www.nature.com/nature/journal/v446/n7132/full/446147a.html
50 & 100 Years Ago p150
10.1038/446150a
http://www.nature.com/nature/journal/v446/n7132/full/446150a.html
Planetary science: Water cycling on Mars pp150 - 151
The Meridiani Planum region on Mars is rich in minerals derived from
evaporation, but lacks a topography consistent with standing water. Do
the deposits stem from upwelling groundwater early in the planet's
history?
Victor R. Baker
10.1038/446150b
http://www.nature.com/nature/journal/v446/n7132/full/446150b.html
Plant biology: The force from without pp151 - 152
It seems that the epidermis is the cell layer through which
growth-promoting plant hormones called brassinosteroids exert their
effect on cell expansion ― a finding that puts a new perspective on
classical views of plant growth.
Ben Scheres
10.1038/446151a
http://www.nature.com/nature/journal/v446/n7132/full/446151a.html
Correction p152
10.1038/446152a
http://www.nature.com/nature/journal/v446/n7132/full/446152a.html
----------------------
ARTICLE
----------------------
Patterns of somatic mutation in human cancer genomes pp153 - 158
518 protein kinase genes in the human genome have been sequenced in a
large sample of tumours, providing a global view of the patterns of
mutations found and the variations in the number and type of mutations
between individual tumours.
Christopher Greenman et al.
10.1038/nature05610
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05610.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05610.html
----------------------
LETTERS
----------------------
An ancient nova shell around the dwarf nova Z Camelopardalis pp159
- 162
Classical novae are thousands of times brighter than dwarf novae, and
are accompanied by the formation of shells around the system. This
paper reports the discovery of a shell an order of magnitude more
extended than those detected around many other classical novae
surrounding the prototypical dwarf nova Z Camelopardalis, thereby
observationally linking the objects.
Michael M. Shara et al.
10.1038/nature05576
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05576.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05576.html
Meridiani Planum and the global hydrology of Mars pp163 - 166
Jeffrey C. Andrews-Hanna, Roger J. Phillips and Maria T. Zuber
10.1038/nature05594
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05594.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05594.html
Observation of the two-channel Kondo effect pp167 - 171
The sought-after exotic two-channel Kondo effect has now been observed
in quantum dots. This effect, where electrons in two electrodes are
entangled with each other through their interaction with a single
localized spin in a quantum dot, has so far been difficult to observe,
as unlike the conventional Kondo effect, this new effect cannot be
described within the conventional picture for electron behaviour of
Fermi liquids.
R. M. Potok et al.
10.1038/nature05556
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05556.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05556.html
Chemical reduction of three-dimensional silica micro-assemblies into
microporous silicon replicas pp172 - 175
This paper reports the 'low temperature' chemical reduction of silica
microshells of the diatom Aulacoseira into silicon replicas.
Structural and chemical analysis reveals an interconnected network of
silicon nanocrystals, maintaining the original intricate
three-dimensional microporous structure of the frustules.
Zhihao Bao et al.
10.1038/nature05570
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05570.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05570.html
Continental ice in Greenland during the Eocene and Oligocene pp176
- 179
This paper reports stratigraphically extensive ice-rafted debris,
including macroscopic dropstones, in late Eocene to early Oligocene
sediments from Norwegian-Greenland Sea, that were deposited between ～
38 and 30 million years ago. The data suggest the existence of at
least isolated glaciers on Greenland about 20 million years earlier
than previously documented, at a time when temperatures and
atmospheric carbon dioxide concentrations were substantially higher.
James S. Eldrett et al.
10.1038/nature05591
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05591.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05591.html
Origin of avian genome size and structure in non-avian
dinosaurs pp180 - 184
A correlate of flight in vertebrates is a reduction of the genome. But
does flight cause genome loss, or does genome loss predispose animals
to take flight? Histology and statistical techniques shows that genome
reduction can be traced deep into the lineage of saurischian
dinosaurs. Genome reduction thus joins the morphological features we
now associate with birds that can be traced far back into the
dinosaurian ancestry.
Chris L. Organ et al.
10.1038/nature05621
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05621.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05621.html
A single type of progenitor cell maintains normal epidermis pp185
- 189
An alternative model for the homeostasis of adult epidermis posits
posits only one type of stem cell undergoes both symmetric and
asymmetric divisions to ensure epidermal homeostasis. A genetic
approach of marking single cells in the adult mouse tail epidermis
shows that the clones of labelled cells that arise from their
inducible labelling approach are most likely to come from a single
compartment of proliferating cells, which may undergo an unlimited
number of divisions.
Elizabeth Clayton et al.
10.1038/nature05574
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05574.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05574.html
Hippocampal remapping and grid realignment in entorhinal cortex pp190
- 194
Marianne Fyhn et al.
10.1038/nature05601
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05601.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05601.html
A cytosolic trans-activation domain essential for ammonium
uptake pp195 - 198
D. Loque et al.
10.1038/nature05579
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05579.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05579.html
The epidermis both drives and restricts plant shoot growth pp199
- 202
Plant shoots are derived from three tissue types, but which tissues
drive or restrict growth has long been debated. A targeted expression
of steroid genes in their corresponding dwarf mutant backgrounds is
used to conclude that the epidermis both drives and restricts shoot
growth.
Sigal Savaldi-Goldstein, Charles Peto and Joanne Chory
10.1038/nature05618
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05618.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05618.html
C5L2 is critical for the biological activities of the anaphylatoxins
C5a and C3a pp203 - 207
Nien-Jung Chen et al.
10.1038/nature05559
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05559.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05559.html
Endonuclease-independent LINE-1 retrotransposition at mammalian
telomeres pp208 - 212
Tammy A. Morrish et al.
10.1038/nature05560
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05560.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05560.html
Structure of an ABC transporter in complex with its binding
protein pp213 - 216
The structure of a putative molybdate transporter (ModB2C2) is
presented in complex with its cognate binding protein ModA. These
results help provide the structural basis for the ATP-driven transport
mechanism of both clinically relevant multi-drug ABC exporters and of
ABC importers facilitating bacterial nutrient uptake.
Kaspar Hollenstein, Dominik C. Frei and Kaspar P. Locher
10.1038/nature05626
Abstract:
http://www.nature.com/nature/journal/v446/n7132/abs/nature05626.html
Article:
http://www.nature.com/nature/journal/v446/n7132/full/nature05626.html
*****
Nature
Copyright Macmillan Publishers Ltd 2004 Registered No. 785998 England.
Nature's worldwide offices:
London . Munich . New Delhi . Tokyo . San Diego . San Francisco ．
Washington . New York
转自：
http://www.biooo.com/bbs/ShowPost.asp?ThreadID=162569 |
|
置顶卡
变色卡
千斤顶
显身卡