Volume 491 Issue 7423



News Features

News & Views

Translational medicineMice and men show the way p.196

Disorders caused by single genes, such as fragile X syndrome, share symptoms with the genetically complex autism spectrum disorders. It emerges that effective drugs for the former may lead to therapies for the latter.

doi: 10.1038/491196a

ImagingThe fog clears p.197

A technique has been developed to image a fluorescent object hiding behind a light-scattering screen without the need for a detector behind the screen. The approach could find applications in imaging biological tissue. See Letter p.232

doi: 10.1038/491197a

BiochemistryA glimpse of molecular competition p.198

Single-molecule studies reveal how the DNA-repair protein RecA overcomes competition from another protein to bind to single-stranded DNA, and how other mediator proteins assist in this process. See Letter p.274

doi: 10.1038/nature11639

AstronomyMeet our closest neighbour p.200

The discovery of a possible extrasolar planet that has the same mass as Earth and orbits α Centauri B, a member of the closest star system to the Sun, is both a technical achievement and cause for excitement. See Article p.207

doi: 10.1038/nature11636

MicrobiologyBacterial power cords p.201

Geochemical reactions in upper layers of marine sediments are coupled to those in deeper zones. It turns out that centimetre-long bacterial filaments acting as electrical cables are the metabolic link between the layers. See Article p.218

doi: 10.1038/nature11638

Applied physicsBrighter images with no added noise p.202

A special type of optical amplifier based on a vapour of rubidium has been demonstrated that makes faint images brighter without adding noise. This concept could find use in biological imaging and image processing.

doi: 10.1038/491202a

Structural biologyA toolbox for protein design p.204

Some of the principles underlying how amino-acid sequences determine the three-dimensional structures of proteins have been defined. This has enabled a successful approach to designing protein folds from scratch. See Article p.222

doi: 10.1038/491204a

AstrophysicsCosmic explosions in the young Universe p.205

The discovery of two superluminous supernovae at large distances from Earth pushes the frontier of supernova studies to just 1.5 billion years after the Big Bang, and suggests that they may be common in the young Universe. See Letter p.228

doi: 10.1038/nature11643


An Earth-mass planet orbiting α Centauri B p.207

Exoplanets down to the size of Earth have been found, but not in the habitable zone—that is, at a distance from the parent star at which water, if present, would be liquid. There are planets in the habitable zone of stars cooler than our Sun, but for reasons such as tidal locking and strong stellar activity, they are unlikely to harbour water–carbon life as we know it. The detection of a habitable Earth-mass planet orbiting a star similar to our Sun is extremely difficult, because such a signal is overwhelmed by stellar perturbations. Here we report the detection of an Earth-mass planet orbiting our neighbour star α Centauri B, a member of the closest stellar system to the Sun. The planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star (one astronomical unit is the Earth–Sun distance).

doi: 10.1038/nature11572

Input-specific control of reward and aversion in the ventral tegmental area p.212

Ventral tegmental area (VTA) dopamine neurons have important roles in adaptive and pathological brain functions related to reward and motivation. However, it is unknown whether subpopulations of VTA dopamine neurons participate in distinct circuits that encode different motivational signatures, and whether inputs to the VTA differentially modulate such circuits. Here we show that, because of differences in synaptic connectivity, activation of inputs to the VTA from the laterodorsal tegmentum and the lateral habenula elicit reward and aversion in mice, respectively. Laterodorsal tegmentum neurons preferentially synapse on dopamine neurons projecting to the nucleus accumbens lateral shell, whereas lateral habenula neurons synapse primarily on dopamine neurons projecting to the medial prefrontal cortex as well as on GABAergic (γ-aminobutyric-acid-containing) neurons in the rostromedial tegmental nucleus. These results establish that distinct VTA circuits generate reward and aversion, and thereby provide a new framework for understanding the circuit basis of adaptive and pathological motivated behaviours.

doi: 10.1038/nature11527

Filamentous bacteria transport electrons over centimetre distances p.218

Oxygen consumption in marine sediments is often coupled to the oxidation of sulphide generated by degradation of organic matter in deeper, oxygen-free layers. Geochemical observations have shown that this coupling can be mediated by electric currents carried by unidentified electron transporters across centimetre-wide zones. Here we present evidence that the native conductors are long, filamentous bacteria. They abounded in sediment zones with electric currents and along their length they contained strings with distinct properties in accordance with a function as electron transporters. Living, electrical cables add a new dimension to the understanding of interactions in nature and may find use in technology development.

doi: 10.1038/nature11586

Principles for designing ideal protein structures p.222

Unlike random heteropolymers, natural proteins fold into unique ordered structures. Understanding how these are encoded in amino-acid sequences is complicated by energetically unfavourable non-ideal features—for example kinked α-helices, bulged β-strands, strained loops and buried polar groups—that arise in proteins from evolutionary selection for biological function or from neutral drift. Here we describe an approach to designing ideal protein structures stabilized by completely consistent local and non-local interactions. The approach is based on a set of rules relating secondary structure patterns to protein tertiary motifs, which make possible the design of funnel-shaped protein folding energy landscapes leading into the target folded state. Guided by these rules, we designed sequences predicted to fold into ideal protein structures consisting of α-helices, β-strands and minimal loops. Designs for five different topologies were found to be monomeric and very stable and to adopt structures in solution nearly identical to the computational models. These results illuminate how the folding funnels of natural proteins arise and provide the foundation for engineering a new generation of functional proteins free from natural evolution.

doi: 10.1038/nature11600