Strong magnetic fields in normal galaxies at high redshift

The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It was recently demonstrated that field strengths as traced by rotation measures of distant (and hence ancient) quasars are comparable to those seen today, but it was unclear whether the high fields were in the unusual environments of the quasars themselves or distributed along the lines of sight. Here we report high-resolution spectra that demonstrate that the quasars with strong Mg II absorption lines are unambiguously associated with larger rotation measures. Because Mg ii absorption occurs in the haloes of normal galaxies along the sightlines to the quasars, this association requires that organized fields of surprisingly high strengths are associated with normal galaxies when the Universe was only about one-third of its present age.     

The formation and assembly of a typical star-forming galaxy at redshift z approximately 3

Recent studies of galaxies approximately 2-3 Gyr after the Big Bang have revealed large, rotating disks, similar to those of galaxies today. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation indicates that gas accretion is likely to be the dominant mode by which galaxies grow, because major mergers of galaxies would completely disrupt the observed velocity fields. But poor spatial resolution and sensitivity have hampered this interpretation; such studies have been limited to the largest and most luminous galaxies, which may have fundamentally different modes of assembly from those of more typical galaxies (which are thought to grow into the spheroidal components at the centres of galaxies similar to the Milky Way). Here we report observations of a typical star-forming galaxy at z = 3.07, with a linear resolution of approximately 100 parsecs. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to be assembling a spheroidal bulge similar to those seen in spiral galaxies at the present day. The presence of undisrupted rotation may indicate that galaxies such as the Milky Way gain much of their mass by accretion rather than major mergers.     

The earliest record of human activity in northern Europe

The colonization of Eurasia by early humans is a key event after their spread out of Africa, but the nature, timing and ecological context of the earliest human occupation of northwest Europe is uncertain and has been the subject of intense debate. The southern Caucasus was occupied about 1.8 million years (Myr) ago, whereas human remains from Atapuerca-TD6, Spain (more than 780 kyr ago) and Ceprano, Italy (about 800 kyr ago) show that early Homo had dispersed to the Mediterranean hinterland before the Brunhes-Matuyama magnetic polarity reversal (780 kyr ago). Until now, the earliest uncontested artefacts from northern Europe were much younger, suggesting that humans were unable to colonize northern latitudes until about 500 kyr ago. Here we report flint artefacts from the Cromer Forest-bed Formation at Pakefield (52 degrees N), Suffolk, UK, from an interglacial sequence yielding a diverse range of plant and animal fossils. Event and lithostratigraphy, palaeomagnetism, amino acid geochronology and biostratigraphy indicate that the artefacts date to the early part of the Brunhes Chron (about 700 kyr ago) and thus represent the earliest unequivocal evidence for human presence north of the Alps.     

World Year of Physics: a direct test of E=mc2

One of the most striking predictions of Einstein's special theory of relativity is also perhaps the best known formula in all of science: E=mc(2). If this equation were found to be even slightly incorrect, the impact would be enormous--given the degree to which special relativity is woven into the theoretical fabric of modern physics and into everyday applications such as global positioning systems. Here we test this mass-energy relationship directly by combining very accurate measurements of atomic-mass difference, Delta(m), and of gamma-ray wavelengths to determine E, the nuclear binding energy, for isotopes of silicon and sulphur. Einstein's relationship is separately confirmed in two tests, which yield a combined result of 1-Delta(mc2)/E=(-1.4+/-4.4)x10(-7), indicating that it holds to a level of at least 0.00004%. To our knowledge, this is the most precise direct test of the famous equation yet described.     

Towards a proteome-scale map of the human protein-protein interaction network

Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.     

Structure of the E. coli protein-conducting channel bound to a translating ribosome

Secreted and membrane proteins are translocated across or into cell membranes through a protein-conducting channel (PCC). Here we present a cryo-electron microscopy reconstruction of the Escherichia coli PCC, SecYEG, complexed with the ribosome and a nascent chain containing a signal anchor. This reconstruction shows a messenger RNA, three transfer RNAs, the nascent chain, and detailed features of both a translocating PCC and a second, non-translocating PCC bound to mRNA hairpins. The translocating PCC forms connections with ribosomal RNA hairpins on two sides and ribosomal proteins at the back, leaving a frontal opening. Normal mode-based flexible fitting of the archaeal SecYEbeta structure into the PCC electron microscopy densities favours a front-to-front arrangement of two SecYEG complexes in the PCC, and supports channel formation by the opening of two linked SecY halves during polypeptide translocation. On the basis of our observation in the translocating PCC of two segregated pores with different degrees of access to bulk lipid, we propose a model for co-translational protein translocation.     

Simulations of the formation, evolution and clustering of galaxies and quasars

The cold dark matter model has become the leading theoretical picture for the formation of structure in the Universe. This model, together with the theory of cosmic inflation, makes a clear prediction for the initial conditions for structure formation and predicts that structures grow hierarchically through gravitational instability. Testing this model requires that the precise measurements delivered by galaxy surveys can be compared to robust and equally precise theoretical calculations. Here we present a simulation of the growth of dark matter structure using 2,160(3) particles, following them from redshift z = 127 to the present in a cube-shaped region 2.230 billion lightyears on a side. In postprocessing, we also follow the formation and evolution of the galaxies and quasars. We show that baryon-induced features in the initial conditions of the Universe are reflected in distorted form in the low-redshift galaxy distribution, an effect that can be used to constrain the nature of dark energy with future generations of observational surveys of galaxies.