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Volume 466 Issue 7303, 8 July 2010

A collaborative project for the accurate measurement of the radius of the proton, a basic subatomic component of all ordinary matter, has arrived at a surprising result. The new value for the protons root-mean-square charge radius — determined spectroscopically in muonic hydrogen in which the electron is replaced by the heavier muon &8211; is about 4% smaller than the previous best value. [Credit: Markus Fischer, Paul Piwnicki, Aldo Antognini/Paul Scherrer Inst.]

Editorial

  • Editorial |

    A legal challenge to US stem-cell policy poses a serious threat to the federal funding system.

  • Editorial |

    There are tools to detect non-originality in articles, but instilling ethical norms remains essential.

  • Editorial |

    Developing drugs for rare diseases is a challenge that requires new regulatory flexibility.

Research Highlights

Journal Club

News

News Feature

  • News Feature |

    A once-threatened population of African fish is now providing a view of evolution in action. Laura Spinney asks what Lake Victoria cichlids have revealed about speciation.

    • Laura Spinney
  • News Feature |

    Finds in Turkey could answer key questions about ancient human origins, but palaeoanthropologists there must first bury their disputes. Rex Dalton reports from the field.

    • Rex Dalton

Correspondence

Opinion

  • Opinion |

    Fifty years after setting foot in Gombe, Jane Goodall calls for urgent action to save our closest living relatives from extinction in the wild. Conservationists and local people must collaborate, she and Lilian Pintea conclude.

    • Jane Goodall
    • Lilian Pintea
  • Opinion |

    Researchers and regulators need to keep up with the changing risks, and share information, says Arne Jernelöv, as tanker spills decline and pipeline leaks and blowouts become more of a concern.

    • Arne Jernelöv
  • Opinion |

    The value of ecosystems is largely invisible to markets. Ricardo Bayon and Michael Jenkins call on governments to drive regulatory and voluntary economic instruments that put a price on the services that nature provides.

    • Ricardo Bayon
    • Michael Jenkins

Books & Arts

News & Views

  • News & Views |

    A site in Norfolk, UK, provides the earliest and northernmost evidence of human expansion into Eurasia. Environmental indicators suggest that these early Britons could adapt to a range of climatic conditions.

    • Andrew P. Roberts
    • Rainer Grün
  • News & Views |

    The discovery that the face-centred cubic form of the fullerene Cs3C60 is a superconductor, just as its body-centred cubic counterpart is, sheds light on the origin of superconductivity in organic materials.

    • Yoshihiro Iwasa
  • News & Views |

    Measuring the tension forces at specific sites in living cells is technically challenging. Now, a fluorescent biosensor protein can be used to characterize dynamic local changes in tension in migrating cells.

    • Andrew D. Doyle
    • Kenneth M. Yamada
  • News & Views |

    Can small molecules in test tubes form assemblies containing different hydrophobic domains, like those found in cells? Yes, finds a study, suggesting new ways of isolating incompatible compounds in water.

    • Jan H. van Esch
  • News & Views |

    Cocaine abuse results in increased craving for the drug. But in the long run, cocaine intake induces the expression of a microRNA in the brain, and this seems to limit further drug intake.

    • Marina R. Picciotto
  • News & Views |

    A measurement of the size of the proton, obtained using spectroscopy of an exotic atomic system, yields a result of unprecedented accuracy — but in disagreement with values obtained by previous methods.

    • Jeff Flowers

Article

  • Article |

    Extended cocaine taking triggers several structural and functional changes in the brain that may lead to compulsive drug seeking, but the mechanisms that regulate the process are unclear. Here, a microRNA — miR-212 — is identified that is upregulated in the striatum of rats with a history of extended access to cocaine. The authors suggest that miR-212 protects against the development of compulsive drug taking, and that it may act through the CREB protein, a known regulator of the rewarding effects of cocaine.

    • Jonathan A. Hollander
    • Heh-In Im
    • Paul J. Kenny
  • Article |

    K+ channels can convert between conductive and non-conductive forms through mechanisms that range from flicker transitions (which occur in microseconds) to C-type inactivation (which occurs on millisecond to second timescales). Here, the crystal structures are presented of the potassium channel KcsA in an open-inactivated conformation and 'trapped' in several partially open conformations. The structures indicate a molecular basis for C-type inactivation in K+ channels.

    • Luis G. Cuello
    • Vishwanath Jogini
    • Eduardo Perozo

Letter

  • Letter |

    Ultraluminous X-ray sources are the most luminous class of black hole located outside the nuclei of active galaxies. They are often associated with shock-ionized nebulae, though with no evidence of collimated jets. Now, however, it is reported that the large nebula S26 in the nearby galaxy NGC 7793 is powered by a black hole with a pair of collimated jets. The jets seem to be 104 times more energetic than the X-ray emission from the core.

    • Manfred W. Pakull
    • Roberto Soria
    • Christian Motch
  • Letter |

    Here, a technically challenging spectroscopic experiment is described: the measurement of the muonic Lamb shift. The results lead to a new determination of the charge radius of the proton. The new value is 5.0 standard deviations smaller than the previous world average, a large discrepancy that remains unexplained. Possible implications of the new finding are that the value of the Rydberg constant will need to be revised, or that the validity of quantum electrodynamics theory is called into question.

    • Randolf Pohl
    • Aldo Antognini
    • Franz Kottmann
  • Letter |

    Quantum information science requires a source of entangled photon pairs, but existing sources suffer from a low intrinsic efficiency or poor extraction efficiency. Collecting emitted photons from quantum dots can be improved by coupling the dots to an optical cavity, but this is not easy for entangled photon pairs. Now, a suitable optical cavity has been made in the form of a 'photonic' molecule — two identical, connecting microcavities that are deterministically coupled to the optically active modes of a pre-selected quantum dot.

    • Adrien Dousse
    • Jan Suffczyński
    • Pascale Senellart
  • Letter |

    Superconductivity and magnetic order are well known in C60 compounds of the form A3C60 (where A = alkali metal). The spherical C60 molecular ions in these crystals are almost always arranged in a face-centred cubic (f.c.c.) packing, except in Cs3C60, where the known superconducting phase has a body-centred cubic (b.c.c) packing. Now the f.c.c. polymorph for Cs3C60 has been isolated; it too is superconducting, although its magnetic properties are very different to those of its b.c.c counterpart.

    • Alexey Y. Ganin
    • Yasuhiro Takabayashi
    • Kosmas Prassides
  • Letter |

    Emissions of African dust increased sharply in the early 1970s, but the human contribution to land degradation and dust mobilization remains poorly understood. Now, a 3,200-year record of dust deposition off northwest Africa has been constructed. On the basis of this dust record and a proxy record for West African precipitation, it is suggested that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for more than 200 years.

    • Stefan Mulitza
    • David Heslop
    • Michael Schulz
  • Letter |

    Hominins colonized Eurasia fairly swiftly after they left Africa around 1.75 million years ago, although it had been thought that they did not penetrate beyond 45° N except in very warm intervals. Now, however, artefacts, fauna and flora dating back more 0.78 million years have been found in a river deposit in Norfolk, England. The findings show that humans were capable of penetrating northern Europe in cooler intervals, and will prompt a re-evaluation of the adaptations and abilities of humans at this early date.

    • Simon A. Parfitt
    • Nick M. Ashton
    • Chris B. Stringer

    Collection:

  • Letter |

    One of the steps in the evolution of tetrapod limbs was the loss of the distinctive fringe of fin rays and fin folds found in the fins of fishes. It is now shown that two novel proteins, actinodin 1 and 2, are essential structural components of fin rays and fin folds in zebrafish, and are also encoded in the genomes of other teleost fish and at least one species of shark, but not in tetrapods. It is suggested that the loss of these genes may have contributed to the fin-to-limb transition in tetrapod evolution.

    • Jing Zhang
    • Purva Wagh
    • Marie-Andrée Akimenko
  • Letter |

    Genomic data from 14 Jewish Diaspora communities are here compared with data from 69 Old World non-Jewish populations, to investigate the demographic history of the Jewish people. Analyses shed new light on relationships between communities, reveal unappreciated genetic substructure within the Middle East, and trace the origins of most Jewish Diaspora communities to the Levant.

    • Doron M. Behar
    • Bayazit Yunusbayev
    • Richard Villems
  • Letter |

    Sialic acid acetylesterase (SIAE) is an enzyme that is involved in B-cell activation and is required to maintain immunological tolerance in mice. It is shown here that rare, inherited and functionally defective SIAE variants are associated with a variety of autoimmune diseases in humans. The study provides one of the first examples of the importance of rare genetic variants in complex diseases, such as those involving autoimmunity.

    • Ira Surolia
    • Stephan P. Pirnie
    • Shiv Pillai
  • Letter |

    Most animal embryos grow through cell accumulation in a posterior growth zone, but the underlying forces are unknown. It is now proposed that posterior elongation in chicken embryos is an emergent property that arises from graded cell motility in random directions (as opposed to directed movement). This occurs in response to signalling through the fibroblast growth factor.

    • Bertrand Bénazéraf
    • Paul Francois
    • Olivier Pourquié
  • Letter |

    The methylation of DNA in 5′ promoter regions suppresses gene expression, but what is the role of DNA methylation in the bodies of genes? Here, a map of DNA methylation is generated from human brain tissue; it is found that most methylated CpG islands are within intragenic and intergenic regions, rather than within promoters. It is proposed that intragenic methylation regulates the expression of alternative gene transcripts in different tissues and cell types.

    • Alika K. Maunakea
    • Raman P. Nagarajan
    • Joseph F. Costello
  • Letter |

    The lysine residues of histone proteins can be acetylated or methylated, with important effects on gene expression. Until recently the protein modules that bind acetyl-lysine have been limited to bromodomains. However, the tandem plant homeodomain (PHD) finger of human DPF3b — which is involved in gene activation — has also been reported to bind to acetylated histones. Here, three-dimensional solution structures of DPF3b offer mechanistic insight into how this protein recognizes acetylation marks.

    • Lei Zeng
    • Qiang Zhang
    • Ming-Ming Zhou
  • Letter |

    The ability of cells to respond to physical forces is central to development and physiology, but until now it has been difficult to directly measure forces across proteins in vivo. Here, however, a calibrated biosensor is described that can measure forces with high sensitivity across specific proteins in cells. This is applied to the vinculin protein, and a regulatory mechanism is revealed in which the force applied to vinculin determines whether focal adhesions assemble or disassemble.

    • Carsten Grashoff
    • Brenton D. Hoffman
    • Martin A. Schwartz
  • Letter |

    Multicellular organisms, particularly their immune systems, rely on complex cell-to-cell communication, mediated by signalling molecules that form spatiotemporal concentration gradients. Here, high-throughput microfluidic cell culture and fluorescence microscopy, together with quantitative gene expression analysis and mathematical modelling, have been used to investigate how mammalian cells respond to different levels of TNF-α and signal to NF-κB. Both digital and analogue responses are revealed.

    • Savaş Tay
    • Jacob J. Hughey
    • Markus W. Covert
  • Letter |

    K+ channels can convert between conductive and non-conductive forms through mechanisms that range from flicker transitions (which occur in microseconds) to C-type inactivation (which occurs on millisecond to second timescales). Here, the mechanisms are revealed through which movements of the inner gate of the K+ channel KcsA trigger conformational changes at the selectivity filter, leading to the non-conductive C-type inactivated state.

    • Luis G. Cuello
    • Vishwanath Jogini
    • Eduardo Perozo

Retraction

Careers Q&A

  • Careers Q&A |

    Heidi Newberg, a physicist and astronomer at Rensselaer Polytechnic Institute in Troy, New York, has won a National Science Foundation grant to create the first partnership between a US team and a Chinese-led astronomy project.

    • Virginia Gewin

Career Brief

Careers and Recruitment

  • Careers and Recruitment |

    With jobs at pharmaceutical companies evaporating, working for a contract research organization is an attractive option for some. Heidi Ledford details the growing market.

    • Heidi Ledford

Futures

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