Extracts from selected News & Views articles published this year.
Resolution beyond the diffraction limit
Jian-Ren Shen (Nature 530, 168–169; 2016)
The resolution at which structures can be visualized using X-ray crystallography depends on the diffraction limit, which in turn depends on the regular arrangement of molecules within crystals. The degree of regularity is often low in crystals of biomacromolecules, creating a major barrier to visualizing these molecules at the atomic level. Ayyer et al. report an approach to solving molecular structures at resolutions higher than the diffraction limit. They propose that molecules in crystals can be considered as rigid units, and that disorder is caused by translational displacements of these units from their lattice positions. These displacements cause scattered X-rays to produce a vague pattern of light and shadowy regions, which contains information about the molecules' structure at resolutions beyond the limit of normal Bragg diffraction. The authors used this information to extend the resolution of a membrane-protein complex from 4.5 Å to 3.5 Å. The technique is potentially a great step forward for those seeking high-resolution structural information for many 'poorly diffracting' protein crystals.
Original research: Nature 530, 202–206 (2016).
A milestone in quantum computing
Stephen D. Bartlett (Nature 536, 35–36; 2016)
Quantum-savvy entrepreneurs are already bringing the first quantum computer processors out of the physics laboratory and onto the market. But these devices are mostly designed to perform just one function and cannot be programmed to run different algorithms. It would therefore be advantageous to build a fully fledged quantum computer that could be programmed to run anything we might want. In particular, it might execute the complex quantum algorithms that researchers think will solve today's intractable problems in quantum chemistry, materials science and data security. Debnath et al. present a small but fully programmable quantum computer consisting of five quantum bits (qubits), and they demonstrate its functionality by running several simple quantum algorithms. In all of these demonstrations, the resulting error rate is consistent with the authors' observations of how their qubits work in isolation, showing that the qubits can be used together in more-sophisticated algorithms in the future. The next challenge for such technologies is to demonstrate that quantum error correction can bring error rates down to negligible levels.
Original research: Nature 536, 63–66 (2016).
Insect invasions and natural selection
Amro Zayed (Nature 539, 500–502; 2016)
The success of social-insect invaders is paradoxical, because they have a sex-determination system that gives rise to many sterile or inviable males in small founding populations. Gloag et al. show how, during the early stages of an invasion of the Asian honeybee Apis cerana, the action of natural selection can lessen this problem. Sex determination in bees is governed by a gene called csd. Different versions of genes are called alleles. Under conditions in which fertilized eggs have two identical alleles of csd, fertilized eggs produce males that are sterile or inviable. The authors speculated that a form of natural selection, called balancing selection, would have a role in reducing imbalances in the frequency of csd alleles. With balancing selection, individuals that have rare csd alleles would be expected to have high fitness. Gloag et al. sequenced the csd gene in the A. cerana population to determine how it evolved during the invasion. They found that the frequency of the csd alleles started to converge on the frequency expected if balancing selection is assumed.
Original research: Nature Ecol. Evol. http://dx.doi.org/10.1038/S41559-016-0011 (2016).
Evidence of life in Earth's oldest rocks
Abigail C. Allwood (Nature 537, 500–501; 2016)
When did life first arise on Earth? Nutman et al. analysed 3.7-billion-year-old rocks in the Isua Greenstone belt in Greenland. Within the rocks can be seen ancient ripple marks and piles of rock fragments deposited during an ancient storm. In the middle of it all are structures resembling stromatolites: layered structures that form through microbially influenced accretion of sediment. If these are really the figurative tombstones of our earliest ancestors, the implications are staggering. Earth's surface 3.7 billion years ago was a tumultuous place. If life could find a foothold here, and leave such an imprint that vestiges exist, even though only a minuscule sliver of rock is all that remains from that time, then life is not a fussy, reluctant and unlikely thing. Give life half an opportunity and it'll run with it.
Original research: Nature 537, 535–538 (2016).
Barbara Mazzolai & Virgilio Mattoli (Nature 536, 400–401; 2016)
Robots are typically used in manufacturing contexts that involve well-structured environments. But if these machines were moved into 'real' environments, they would have to cope with uncertain situations and adapt to changing conditions — tough problems to solve using conventional technology made from hard materials. Robots made from soft, deformable materials would be better able to grasp and manipulate unknown objects, and to move on unstructured and rough terrains. Wehner et al. present the first robot that completely lacks rigid structures and control systems. The octopus-shaped robot has eight arms moved by a mechanism that relies on the expansion of embedded, inflatable components integrated into a fluidic-pneumatic network, powered by a liquid fuel. Although soft robotics is still in its infancy, it holds great promise for applications such as servicing and inspecting machinery, search-and-rescue operations, and exploration.
Original research: Nature 536, 451–455 (2016).
Virtual reality explored
(Nature 533, 324–325; 2016)
Neuroscientists are increasingly using virtual reality (VR) to facilitate studies of animal behaviour, but whether behaviour in the virtual world mimics that in real life is a matter for debate.
The best of both worlds
Matthias Minderer & Christopher D. Harvey
VR allows researchers to define explicitly and exhaustively the sensory cues that carry information about the virtual world. It offers the means to add or remove sensory cues to test the contribution of each one to a neural code, and to build up a 'minimal' set of stimuli needed to produce a given behaviour or neural activity pattern. A second benefit comes from the ability to redefine the laws that link the subject's actions to changes in its world. Third, VR increases the range of tools available to measure neural activity.
A world away from reality
Flavio Donato & Edvard I. Moser
Pressing concerns are raised when VR is used to study higher-order computations. Navigation reflects the integration of many sensory inputs. But in VR, these elements are often not coordinated, and the animal must overcome discrepancies between visual cues that follow movements and cues that are static in VR, such as smell. Such discrepancies might alter the activity of space-encoding neurons to reflect only information coordinated to motion, such as visually changing landmarks and accumulated distance, at the expense of other cues. This could lead researchers to overestimate the contribution of visual inputs to navigation.
Dawn of a new astronomy
M. Coleman Miller (Nature 531, 40–42; 2016)
Albert Einstein discovered that binary stars and other sources should generate gravitational waves. Unfortunately, he also found that any imaginable source would produce waves so weak that detection was inconceivable using the technology of the day. But this inconceivable detection has now been reported by Abbott et al. (the LIGO Scientific Collaboration and the Virgo Collaboration) in Physical Review Letters. The authors describe the detection of the signal GW150914 from gravitational waves generated by the merger of two black holes. Astronomers previously had only three types of messenger from space beyond our Solar System: photons, neutrinos and high-energy cosmic rays. Gravitational waves can now be added to this short list. Opening this window will reveal astronomical events that had only been hypothesized. The signal has also provided the most direct confirmation yet of the existence of event horizons — the boundaries beyond which nothing can escape a black hole's gravitational field.
Original research: Phys. Rev. Lett. 116, 061102 (2016).
From sea to sea
Susan L. Williams (Nature 530, 290–291; 2016)
Eelgrass (Zostera marina) is an unlikely model for plant evolution, but is a useful one because it has undergone major habitat shifts: it evolved from marine algae into a terrestrial flowering plant, then moved back to the sea again. Olsen et al. describe the complete genome sequence of eelgrass. The sequence reveals that, in moving from calm lakes and ponds to the rough, salty ocean, eelgrass lost several key gene groups. For evolutionary biologists, the genome represents a missing piece in the puzzle of angiosperm evolution. For marine ecologists, the genome is a powerful tool for uncovering the adaptations that allow the plant to thrive in a wide range of environmental conditions. This ability to adapt might be the key to surviving environmental changes such as ocean acidification, warming and freshening that are occurring under global climate change.
Original research: Nature 530, 331–335 (2016).