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Researchers from Harvard University and the Massachusetts Institute of Technology show that graphene, when used as a membrane to separate two liquid reservoirs, is strongly ionically insulating yet its in-plane electronic properties are strongly dependent on the environment on each side of the membrane. Various analytical applications may result from this behaviour. For instance, if pores measuring a few nanometres in diameter are drilled into these trans-electrode membranes, a long DNA molecule can be threaded through the graphene nanopore; the way in which the molecule behaves as it squeezes through offers a potential basis for DNA-sequencing devices that are far less expensive to operate than current machines. Illustration: Paul Montie Design.
Can epigenetics underlie the enduring effects of a mother's love? Lizzie Buchen investigates the criticisms of a landmark study and the controversial field to which it gave birth.
Taxonomists should work with specialists in pattern recognition, machine learning and artificial intelligence, say Norman MacLeod, Mark Benfield and Phil Culverhouse — more accuracy and less drudgery will result.
Rodney Brooks enjoys an account of the freewheeling group of post-war British researchers that sowed the seeds of robotics through a desire to imitate animal brains and behaviour.
An electrifying evolutionary radiation has evidently occurred among elephant fish in Africa's Ivindo basin. An implication is that open niches for communication can result in species diversification.
Meticulous reconstruction of the former extent of a glacier high in the mountains of New Zealand will help in interpreting global-scale climatic adjustments that occurred at the end of the last glaciation.
Advances in stem-cell technology have broken the barrier to gene targeting in mammals other than mice. A wide array of research opportunities now opens up, especially in studies involving the laboratory rat.
Noise in biochemical processes can compromise precision in cellular functions. An analysis involving information theory suggests that there is a strict limit to how far noise can be suppressed by feedback.
Tiny holes have been drilled through individual layers of graphene — atomically thin sheets of carbon — using an electron beam. These nanopores might be useful for the ultrarapid sequencing of single DNA molecules.
Biological systems avoid molecular noise using feedback loops controlling RNA or protein synthesis, but these reactions rely on the stochastic birth and death of molecules. These authors use control and information theory to show that making a genetic network twice as accurate takes 16 times more signalling steps. Nature must therefore call on brute-force solutions to maintain accuracy, and hence does so only when noise suppression is absolutely vital.
In the ubiquitin–proteasome system, substrates destined for destruction are modified with ubiquitin chains and then degraded by the proteasome. These authors reveal a regulatory mechanism in which proteasomal activity is modulated by the length of ubiquitin chains in human cells. They find that deubiquitinating enzyme USP14 can inhibit the degradation of ubiquitin-conjugated substrates by trimming ubiquitin chains, and that stimulation of proteasome activity may be used to reduce the levels of toxic proteins in cells.
In graphene, two particular sets of electrons exist that have a fourfold energy degeneracy. To study the corresponding four quantum states comprising a Landau level, these authors perform measurements on epitaxial graphene at 10 millikelvin. They take spectral 'fingerprints' of the Landau levels, showing in detail how they evolve with magnetic field and how they split into the four separate quantum states. They also observe states with Landau level filling factors of 7/2, 9/2 and 11/2.
Graphene is highly electronically conducting across the plane of the material. These authors show that a graphene membrane separating two ionic solutions in electrical contact is strongly ionically insulating despite being atomically thin and has in-plane electronic properties dependent on the interfacial environment. Numerical modelling reveals that very high spatial resolution is possible using this system, and the researchers propose that drilled membranes could form the basis of DNA sequencing devices.
The Younger Dryas — during which Northern Hemisphere temperatures cooled drastically in just a few years — is perhaps the best-known example of abrupt climate change, but its global extent is under debate, particularly in the record of glacial behaviour in New Zealand. These authors present evidence for glacial retreat in New Zealand during the Younger Dryas, supporting the hypothesis that Northern Hemisphere climate changes caused Southern Hemisphere warming through a series of climate feedbacks.
These authors show evidence for a high coherence between the slip distribution inferred from the 2010 Maule earthquake, Chile, and the patchwork of interseismic locking distribution derived from global positioning system observations during the previous decade. Their work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future earthquakes, which thus might be anticipated by geodetic observations.
The almost complete and remarkably conserved skeleton of a medium-sized dinosaur was discovered in Las Hoyas, Spain. Phylogenetic analysis places this specimen at the evolutionary base of the Carcharodontosauridae.
Mapping disease loci that underlie putative Mendelian forms of malformations of cortical development is complicated by genetic heterogeneity, small family sizes and diagnostic classifications that may not reflect molecular pathogenesis. These authors use whole-exome sequencing to identify recessive mutations in WDR62 as the cause of a wide spectrum of severe cerebral cortical malformations. WDR62's nuclear localization to germinal neuroepithelia indicates that cortical malformations can be caused by events during progenitor proliferation and neurogenesis.
The rat is a animal model widely used for studying human physiology and disease, but functional genomics and genetic research have been stifled by the limited availability of gene targeting tools. These authors have established gene targeting by homologous recombination in rat embryonic stem cells, and have generated p53 gene knockout rats for the first time.
Human immunodeficiency virus (HIV) fails to induce interferon in the cells that it infects, but the underlying mechanisms are not known. These authors show that the virus can in fact activate the interferon pathway in dendritic cells when the usual block to infection is bypassed. Dendritic cell activation depends on the HIV-1 capsid/cyclophilin A interaction, which is known to have a role in HIV-1 infectivity.
In eukaryotic cells, a subset of microtubules undergo post-translational modifications such as acetylation, which alters microtubule dynamics and trafficking of motors. These authors identify MEC-17 as the enzyme that directly acetylates α-tubulin in vitro and in vivo and in both invertebrates and vertebrates. This is the identification of the long-sought enzyme that acetylates microtubules.
The ends of eukaryotic chromosomes are composed of repeat sequences known as telomeres. Various proteins bind telomeres to protect them from degradation or inappropriate DNA repair responses, and their length is maintained by a specialized reverse transcriptase, telomerase. These authors show that in the absence of telomerase, telomeres can be maintained by amplifying and recombining heterochromatin sequences there. This process requires histone methylation and two telomere-binding proteins, Pot1 and Ccq1.
The ends of chromosomes, known as telomeres, look like ends generated by double-strand breaks, but if treated as such the DNA damage repair system would initiate a checkpoint response and cause telomere–telomere fusions. These authors show that telomeres lack two types of histone modification that are required for recruitment of Crb2b53BP1, without which the checkpoint cannot be activated even if other DNA damage response proteins are recruited to a Taz1-deficient telomere.
Transport of solutes across biological membranes is carried out by specialized secondary transport proteins in the lipid bilayer. These authors report structures of the sodium-independent carnitine/butyrobetaine antiporter CaiT from two microorganisms. The three-dimensional architecture of CaiT resembles that of the Na+-dependent transporters LeuT and BetP, but in CaiT a methionine sulphur takes the place of the Na+ ion to coordinate the substrate in the central transport site, enabling Na+-independent transport to occur.
Stephen Morris, a postdoc at the Centre of Molecular Materials for Photonics and Electronics at the University of Cambridge, UK, is the winner of the 2010 Young Scientist award from the British Liquid Crystal Society.