Research articles

Even after a motor skill is overlearned, some variation remains every time it is performed. Such variation enables trial-and-error learning for adult bengalese finch song. Birds rapidly learned to make adaptive shifts in their vocalizations in response to auditory perturbations delivered to a subset of natural variations in their songs, consistent with the idea that motor variability is a form of exploration that can support continuous learning and optimization of performance.

At the onset of mitosis, the nuclear envelope is diassembled, and is reformed at the end of the process. A mechanistic explanation for the reformation of the nuclear envelope is provided, finding that the chaperone p97 (an AAA ATPase) binds to an ubiquitylated form of Aurora B, an inhibitor of nuclear envelope formation, on chromatin. This results in extraction of Aurora B from chromatin, allowing chromosome decondensation and nuclear envelope formation.

A crystal structure of the plasmid partition protein ParR bound to centromeric DNA is described. ParR binds the centromeric DNA repeats as a dimer-of-dimers, which assemble in a super-helical array to form a large segrosome with a solenoid-shaped structure.

A bioenergetic consumer–resource model is used to explore how and why only particular predator–prey body-mass ratios promote stability in tri-trophic food chains, and finds that this 'persistence domain' of ratios is constrained by bottom-up energy availability when predators are much smaller than their prey, and by enrichment-driven dynamics when predators are much larger.

A tiny disc-like structure on a silicon chip is simply illuminated by a conventional laser diode, and the resulting interaction between the laser light and the resonator gives rise to an optical frequency comb that emits in the infrared. The simplicity of the scheme, and the reduction in size, cost and power, should enhance the utility of optical frequency combs in a broad number of fields.

Autophagy contributes to host defence against infection. Toll like-receptor signals induce the recruitment of components of the autophagy pathway to phagosomes and facilitate phagosome lysosome fusion, resulting in killing of the invading organism.

This paper reports an NMR approach that enables the three-dimensional movement of two linked RNA helices to be followed for a period up to milliseconds. The two helices move in a highly correlated manner, demonstrating both twisting and bending. Results with different liganded conformations demonstrate that the motions of the unstructured RNA maps out positions within the dynamic envelope described by the bound structures.

This paper shows how noisy gene expression causes a bacterial cell to slowly lose track of time, as measured by its circadian clock. The theoretical framework thus introduced breaks the ground for the analysis of noise in other out-of-equilibrium living systems.

Exceptionally high resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey find that the onset of environmental change and surface–ocean warming preceded the input of greenhouse gases by several thousand years. This sequence is consistent with the proposal that warming of the deep ocean caused the dissociation of submarine gas hydrates, which released massive amounts of methane.

This paper reports a study of polarons in a GaAs crystal subject to a strong electric field. In addition to the overall drift motion of the polaron, an oscillatory internal motion is observed in which the electron is impulsively moved away from the centre of the surrounding lattice distortion. Such quantum coherent processes directly affect high-frequency transport in nanostructures.

The first intracellular recordings from presynaptic boutons in the intact mammalian brain are presented. These results contradict the prevailing views (derived from in vitro work) on how the cerebellum integrates sensory information to control movement, by revealing a hitherto unexpected sensitivity of single brain connections to stimuli from the environment.

The transcription factor Nanog is considered a hallmark of pluripotent cells in vivo and in vitro, and loss of Nanog an early marker of differentiation. This is now revised by the demonstration that Nanog is not essential for maintaining pluripotency, but acts in stabilizing the pluripotent state.

A microfluidic platform that is capable of efficiently and selectively separating viable circulating tumour cells (CTCs) from peripheral blood samples has been developed. Low levels of CTCs in the peripheral blood of patients with various cancers were identified, and it was shown that this device could be used to monitor an individual patient's response to anti-cancer therapy.

Stimulation of single neurons in somatosensory cortex affects rats' behavioural responses in a detection task, suggesting a sparser cortical code for sensations than previously anticipated.

The synthesis of SrFeO₂, a new compound bearing a square-planar oxygen coordination around Fe2⁺, is shown. SrFeO₂ is isostructural with 'infinite layer' cupric oxides, and exhibits a magnetic order far above room temperature.

A bosonic excitation (mode) at energies 10.5 ± 2.5 meV in the electron doped superconductor Pr_0.88LaCe_0.12CuO₄ (PLCCO) is reported. The analysis of this indicates an electronic origin of the mode consistent with spin excitations rather than phonons.

The circadian regulator CLOCK has histone acetyltransferase (HAT) activity that contributes to chromatin-remodelling events during circadian control of gene expression. Here, CLOCK is shown to acetylate its heterodimerization partner BMAL1, a step which facilitates recruitment of CRY1 and promotes transcriptional repression.