Letters in 2007

The key to successful social interactions is the ability to accurately assess others' intentions, be they friend or foe. In humans, this ability is present very early on in life, as is shown here when preverbal infants evaluate individuals based on their actions towards others, preferring helpers to neutral or hindering individuals.

The observation of a negative Hall resistance in the magnetic-field-induced normal state of underdoped 'YBCO'materials, which reveals that these pockets are electron-like rather than hole-like. It is proposed that these electron pockets most probably arise from a reconstruction of the Fermi surface caused by the onset of a density-wave phase, as is thought to occur in the electron-doped copper oxides near the onset of antiferromagnetic order.

A microcavity structure to which a periodic potential is applied has been designed, which effectively creates an array of weakly-coupled condensates. This allows the observation of fundamental dynamic behaviour, namely the build-up of certain superfluid-like states, which has been predicted for arrays of atomic Bose–Einstein condensates, but not yet observed.

A drug used as an antidepressant in humans increases Caenorhabditis elegans lifespan. In humans, this drug blocks neural signalling by the neurotransmitter serotonin. In C. elegans, it seems to act as an antagonist for the serotonin receptor and for the receptor of the neurotransmitter octopamine. The drug's effect on lifespan seems to involve mechanisms similar to those that underlie lifespan extension by dietary restriction.

LHCII, the main light-harvesting complex in photosynthesis, has an inbuilt capability to undergo transformation into a dissipative state by conformational change, but it was not known if such events occur in vivo or how energy is dissipated in this state. The transition into the dissipative state is associated with a twist in the configuration of the LHCII-bound carotenoid neoxanthin identified using resonance Raman spectroscopy. Applying this technique to study isolated chloroplasts and whole leaves, this paper shows that the same change in neoxanthin configuration occurs in vivo, to an extent consistent with the magnitude of energy dissipation.

Regulatory T cells suppress immune function by direct cell to cell contact and secretion of the cytokines IL-10 and TGF-β. In this paper, a novel member of the IL-12 cytokine family that contributes to Treg function is identified.

The crystal structure of a SNARE protein bound to a clathrin adaptor is reported, which reveals that there is highly specific interactions between two folded domains as opposed to the linear peptide motif or folded domains that have been described for other families of cargo proteins. This is the first example of a SNARE association with a clathrin adaptor and describes a novel mechanism by which cargo can be recruited into clathrin coated vesicles.

Wood-feeding 'higher' termites rely on their hindgut symbionts for the intitial steps in cellulose degradation. Metagenomic analysis of this microbial community reveals a diverse range of bacterial cellulase and hydrolase genes, as well as genes important in other metabolic functions, such as H2 metabolism, CO₂-reductive acetogenesis and N₂ fixation.

RAG2, a component of the V(D)J recombinase, has a plant homeodomain (PHD) domain which specifically recognizes histone H3 trimethylated at lysine 4 (H3K4me3). A crystal structure of the complex is presented, and the interaction between RAG2 and H3K4me3 shown to be important for V(D)J recombination in vivo.

Tumours are occasionally transferred from donor to recipients during organ transplantation. This paper shows in a mouse model that during latency tumours are actively held in check by the adaptive immune system.

Pico-to-nanosecond timescale atomic fluctuations in hinge regions of adenylate kinase facilitate the large-scale, slower lid motions that produce a catalytically competent state.

Supernova 2006gy in the galaxy NGC 1260 is the most luminous one recorded. Its progenitor might have been a very massive star, but that is incompatible with hydrogen in the spectrum of the supernova. Instead, it might have arisen from the merger of two massive stars. However, the collision frequency of massive stars in a dense and young cluster is sufficient to provide a reasonable chance that SN 2006gy resulted from such a bombardment.

SUV39H1 is the major methyltransferase responsible for tri-methylation of histone H3 at lysine 9 in heterochromatin. The histone deacetylase SIRT1 is shown to target the SUV39H1 enzyme and contribute to elevated levels of SUV39H1 activity and H3K9me3 in heterochromatin.

RNA polymerase II (Pol II) uses a DNA template to direct RNA synthesis during transcription, but there is also emerging evidence that it can use RNA as a template. In this paper the RNA-dependent RNA polymerase activity of Pol II is biochemically and structurally characterized.

At the fundamental level, measurement precision is limited by the number of quantum resources that are used. Standard measurement schemes lead to a phase uncertainty that scales with this number. In principle, it should be possible to achieve a precision limited only by the Heisenberg uncertainty principle. Here, an approach using unentangled single-photon states enables the achievement of Heisenberg-limited phase estimation. This represents a drastic reduction in the complexity of achieving quantum-enhanced measurement precision.

A new approach for achieving strong coupling between optical emitters and their environment is demonstrated by combining techniques and ideas from plasmon and quantum optics. The emitter is a semiconductor quantum dot that is placed near a silver nanowire. Light from the quantum dot can couple directly to guided surface plasmons inside the metallic nanowire, which causes the ends of the nanowire to light up. Spectroscopy measurements indicate that this is the result of single plasmons scattering from the wire end.

A comprehensive organic carbon budget for the Himalayan erosional system is presented, and finds that organic carbon export is controlled by sediment properties and that oxidative loss is negligible during transport and deposition to the ocean. The results indicate that 70 to 85 per cent of the organic carbon is recent organic matter captured during transport, which serves as a net sink for atmospheric carbon dioxide.

Several bacterial pathogens including Pseudomonas aeruginosa use cell-to-cell signalling to regulate virulence factor expression. The cost of communication is believed to allow for cheaters and this paper provides experimental evidence that this is the case, signal and signal-receptor mutants display a fitness advantage. But this advantage decreases with an increase in relatedness of the competing strains, a phenomenon known as kin selection.