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Volume 447 Issue 7143, 24 May 2007

Editorial

  • Equating animal-rights activism with terrorism increases the penalties for offenders and will please many of their victims. But it is not in the interests of science.

    Editorial

    Advertisement

  • A draft law will unnecessarily hinder embryo research.

    Editorial
  • Top scientists should campaign only where they can truly make a difference.

    Editorial
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Research Highlights

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News

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News in Brief

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Correction

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Business

  • Despite its critics, the Alternative Investment Market could still be attractive to America's small, innovative companies, reports Andrea Chipman.

    Business
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News Feature

  • It is 50 years since Arvid Carlsson showed dopamine to be a neurotransmitter. Alison Abbott profiles a chemical and its champion.

    • Alison Abbott
    News Feature
  • Quantum cryptography is theoretically unbreakable, yet a handful of physicists are finding ways to hack into its secrets. Geoff Brumfiel finds out how.

    • Geoff Brumfiel
    News Feature
  • When you win a Nobel prize, you become much in demand. Eric Sorensen takes a look at how laureates decide which worthy causes to lend their name to.

    • Eric Sorensen
    News Feature
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Correspondence

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Commentary

  • European life-science infrastructure has been neglected for too long. The next generation of facilities needs better coordination and community support, argue Iain W. Mattaj and Glauco P. Tocchini-Valentini.

    • Iain W. Mattaj
    • Glauco P. Tocchini-Valentini
    Commentary
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Books & Arts

  • To develop the atomic bomb, J. Robert Oppenheimer changed Los Alamos — and it changed him.

    • Catherine Westfall
    Books & Arts
  • Sink your teeth into Jean Painlevé's nature films at an exhibition in London.

    • Martin Kemp
    Books & Arts
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Essay

  • As the complex interplay of forces in the ocean responds to climate change, the dynamics of global ocean circulation are shifting.

    • Martin Visbeck
    Essay
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News & Views

  • In theory, semiconductor nanocrystals are highly suitable laser materials, not least because the colour of their light is tunable over a wide range. In practice, they are difficult — but not impossible — to deal with.

    • Todd D. Krauss
    News & Views
  • The 'body clock' regulates the daily cycles of many physiological and metabolic processes, but just how is a mystery. New findings suggest that the cycling of energy metabolism is mediated by an activator of gene expression.

    • Benedetto Grimaldi
    • Paolo Sassone-Corsi
    News & Views
  • What forces shape the membranes of the biological cell? A computer simulation indicates that it is the concerted effort of many proteins, mediated by the lipid bilayer that forms the membrane matrix.

    • Michael M. Kozlov
    News & Views
  • MicroRNAs are natural, single-stranded, small RNA molecules thought to control gene expression. Four studies indicate that specific microRNA sequences can regulate heart function in development and disease.

    • Kenneth R. Chien
    News & Views
  • For most of its existence, a superfluid droplet leads an essentially innocuous, classical life. But intense scrutiny reveals that the birth of such droplets is a turbulent and unpredictable quantum affair.

    • Henk T. C. Stoof
    News & Views
  • In bacteria, some messenger RNAs can sense the need for their protein product and accordingly regulate expression of their own genes. A similar type of RNA regulation has now been revealed in higher organisms.

    • Benjamin J. Blencowe
    • May Khanna
    News & Views
  • Do we understand the violent and cosmologically significant stellar explosions known as type-Ia supernovae? Yes and no, as astronomers participating in a conference in California agreed.

    • David Branch
    • Ken'ichi Nomoto
    News & Views
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Introduction

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Review Article

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Article

  • Semiconductor nanocrystals seem good candidates for 'soft' optical gain media, but optical gain and lasing is hard to achieve owing to a fundamental optical effect, which involves the problem that at least two excitons need to be present in a nanocrystal to achieve gain, and this limits performance. Here the problem is circumvented by designing nanocrystals with cores and shells made from different semiconductor materials, and in such a way that electrons and holes are separated from each other: this makes possible optical gain based on single excitons, thereby significantly enhancing the promise of semiconductor nanocrystals as practical optical materials for a wide range of lasing applications.

    • Victor I. Klimov
    • Sergei A. Ivanov
    • Andrei Piryatinski
    Article
  • Several neurodegenerative diseases are caused by expansion of CAG triplet repeats, and, using a mouse model of human Huntington's disease, this study shows that this expansion occurs in mid-life and continues throughout life; furthermore, the expansion occurs in terminally differentiated cells. This is associated with oxidative damage, and deficiency in OGG1, a DNA repair enzyme, attenuates age-dependent repeat expansion — thus it seems that aberrant repair of oxidative damage is the basis for this disease.

    • Irina V. Kovtun
    • Yuan Liu
    • Cynthia T. McMurray
    Article
  • Degenerative diseases such as Alzheimer's or Parkinson's are associated with the misfolding of many diverse proteins, yet the amyloid fibrils formed by all these proteins are similar. David Eisenberg and colleagues have now identified 30 short fibril-forming peptides implicated in a range of amyloid diseases and have solved 13 of their atomic structures, revealing variations in one common feature — the 'steric zipper'.

    • Michael R. Sawaya
    • Shilpa Sambashivan
    • David Eisenberg
    Article
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Letter

  • S. R. Kulkarni and colleagues report the discovery of a mysterious optical transient called M85 OT2006-1 in the outskirts of the lenticular galaxy Messier 85 in the Virgo Cluster. Brighter than novae and fainter than supernovae, it is unlikely to be a giant eruption from a luminous blue variable star because no such star is known to be there, but a possible origin is a stellar merger.

    • S. R. Kulkarni
    • E. O. Ofek
    • D. B. Sanders
    Letter
  • Specialized proteins can sense and create membrane curvature, and direct membrane remodelling, linked to important cellular tasks such as endocytosis and protein sorting; but whether such proteins might be assisted by more generic, universal effects has been unclear. One of the most sophisticated simulation tools available for the task has now been used to confirm that that is indeed the case; membrane curvature caused by simple protein adsorption can drive clustering of proteins lacking any specific interactions, and even induce local membrane transformation into vesicles.

    • Benedict J. Reynwar
    • Gregoria Illya
    • Markus Deserno
    Letter
  • To investigate the links between hurricane activity and climate, this study has constructed a long-term record of intense hurricane activity in the western tropical North Atlantic Ocean by taking sediment cores from a lagoon on the island of Vieques in Puerto Rico, where sand is deposited by hurricanes. The record shows striking similarities to records of El Niño events and rainfall in tropical Africa, suggesting that changes in the El Niño/Southern Oscillation and the strength of the West African monsoon were important in controlling the frequency of intense hurricanes in the tropical North Atlantic over the past 5,000 years.

    • Jeffrey P. Donnelly
    • Jonathan D. Woodruff
    Letter
  • This study bridges two theoretical approaches to model the evolution of cooperation: inclusive fitness models and evolutionary game theory. Simple analytical conditions are found for the evolution of cooperation for a large class of graphs.

    • Peter D. Taylor
    • Troy Day
    • Geoff Wild
    Letter
  • By comparison with modern fishes such as zebrafish, it has long seemed that the limbs of tetrapods are evolutionary innovations unique to tetrapods, but here Marcus Davis and colleagues instead studied Hox-gene expression in the development of the fins of a 'living fossil'. The paddlefish, common in the seas more than 250 million years ago, has Hox-gene patterns long considered to be tetrapod hallmarks, showing that some aspects of limb development are primitive and common to all bony fish, but which have apparently been lost in highly evolved fishes such as the zebrafish.

    • Marcus C. Davis
    • Randall D. Dahn
    • Neil H. Shubin
    Letter
  • Here the metabolic transcriptional regulator PGC-1alpha is identified as a component of the circadian clock in mammals, which regulates glucose and lipid homeostasis and energy metabolism. Mice lacking PGC-1alpha in their liver and muscle show abnormal daily rhythms of activity, body temperature and metabolic rate, correlated with the disruption of clock genes.

    • Chang Liu
    • Siming Li
    • Jiandie D. Lin
    Letter
  • A number of advanced tumours appear to evade immune recognition by natural killer cells by shedding the soluble major histocompatibility complex class-I-related ligand MICA, which inactivates the NKG2D receptor. Now the mechanism of shedding is shown to involve the protein disulphide isomerase ERp5.

    • Brett K. Kaiser
    • Daesong Yim
    • Thomas Spies
    Letter
  • The orientation of the cell division axis is critical for normal growth and development as it determines the fate of future daughter cells; and the extracellular matrix to which cells adhere to plays a role in determining the orientation of the division axis. Here Bornens and colleagues present a combination of experimental and quantitative theory to show that spindle orientation is controlled by cortical force generators; a simple model based on pulling forces exerted by force generators on spindle microtubules can quantitatively describe spindle orientations in many different geometries.

    • Manuel Théry
    • Andrea Jiménez-Dalmaroni
    • Frank Jülicher
    Letter
  • Riboswitches are elements present in some mRNAs that form alternative folded structures depending on the presence or absence of a small molecule ligand. These alternative structures determine whether protein is made from the mRNA. Here, a new way by which riboswitches affect protein expression, by affecting alternative splicing, is described.

    • Ming T. Cheah
    • Andreas Wachter
    • Ronald R. Breaker
    Letter
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Prospects

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Regions

  • Seattle is reaping the benefits of having the world's largest health foundation in its backyard. Eric Sorensen gauges the impact.

    • Eric Sorensen
    Regions
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Movers

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Bricks & Mortar

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Career View

  • Do researchers in my field recognize the challenges of balancing work and kids?

    • Moira Sheehan
    Career View
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Authors

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Insight

  • Genetic mechanisms alone cannot explain how some cellular traits are propagated. Rapid advances in the field of epigenetics are now revealing a molecular basis for how heritable information other than DNA sequence can influence gene function. These advances also add to our understanding of transcriptional regulation, nuclear organization, development and disease.

    Insight
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