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The scanning electron micrograph on the cover, courtesy of Olivier Schwartz of the Pasteur Institute, shows HIV particles (pink pseudocolour) budding at the surface of an infected lymphocyte (blue). Reviews and features in this issue report on progress towards the elusive goal of an effective AIDS vaccine, essential if the AIDS/HIV pandemic is to be contained and HIV-1 eradicated.
The integrity of climate research has taken a very public battering in recent months. Scientists must now emphasize the science, while acknowledging that they are in a street fight.
Translational-research programmes supported by flexible, long-term, large-scale grants are needed to turn advances in basic science into successful vaccines to halt the AIDS epidemic, says Wayne C. Koff.
A proposed reinvention for urban motoring based on ultra-small electric vehicles does not address the bigger environmental or social challenges, finds Daniel Sperling.
In Country Driving, the final book in his China trilogy, Peter Hessler recounts his 11,000-kilometre drive across China to see at first hand the effects of rapid industrialization. The New Yorker journalist explains how mass migration to cities brings out people's resourcefulness, but also how the speed of social and environmental change leads them to seek meaning in their lives.
Every machine is made of parts. But, as the new structure of the HIV integrase enzyme in complex with viral DNA shows, one could not have predicted from the individual parts just how this machine works.
Unexpected chlorine chemistry in the lowest part of the atmosphere can affect the cycling of nitrogen oxides and the production of ozone, and reduce the lifetime of the greenhouse gas methane.
If evolution has had trouble making effective carbohydrate receptors, what hope do humans have of creating synthetic versions? A method for preparing libraries of such receptors boosts the chances of success.
Hormones are not all-powerful in determining whether birds develop with male or female features. Chickens that are genetic sexual mosaics reveal that individual cells also have a say in the matter.
Einstein's theory of general relativity has been tested — and confirmed — on scales far beyond those of our Solar System. But the results don't exclude all alternative theories of gravity.
The integrase protein of retroviruses such as HIV-1 catalyses insertion of the viral genome into that of the host. Here, the long-awaited structure of the full-length integrase complex is predicted, revealing not only details of the biochemistry of the integration reaction, but also the means by which current inhibitors affect this process.
In mammals, embryos are considered to be sexually indifferent until the action of a sex-determining gene initiates gonadal differentiation. Here it is demonstrated that this situation is different for birds. Using rare, naturally occurring chimaeric chickens where one side of the animal appears male and the other female, it is shown that avian somatic cells possess an inherent sex identity and that, in birds, sexual differentiation is cell autonomous.
A new strategy is presented to accurately profile the activity of human genes in endocytosis by combining genome-wide RNAi, automated high-resolution confocal microscopy and quantitative multi-parametric image analysis. Several novel components of endocytosis and endosome trafficking were uncovered; a systems analysis further revealed that the cell regulates the number, size and concentration of cargo within endosomes.
The transcriptome of Helicobacter pylori, an important human pathogen involved in gastric ulcers and cancer, is presented. The approach establishes a model for mapping and annotating the primary transcriptomes of many living species.
Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Now, at a length scale of tens of megaparsecs, the quantity EG, which combines measures of large-scale gravitational lensing, galaxy clustering, and the growth rate of structure, has been measured to be 0.39±0.06, in agreement with the general relativistic prediction of about 0.4.
Measuring the oscillations of a star can allow the various mixing processes in its interior to be disentangled, through the signature they leave on period spacings in the gravity mode spectrum. Here numerous gravity modes in a young star of about seven solar masses are reported: the mean period spacing enables the extent of the convective core to be determined, and the clear periodic deviation from the mean constrains the location of the chemical transition zone — at about 10 per cent of the radius.
An insulator does not conduct electricity, and so cannot in general be used to transmit an electrical signal. But an insulator's electrons possess spin in addition to charge, and so can transmit a signal in the form of a spin wave. Here a hybrid metal–insulator–metal structure is reported, in which an electrical signal in one metal layer is directly converted to a spin wave in the insulating layer; this wave is then transmitted to the second metal layer, where the signal can be directly recovered as an electrical voltage.
When a shape memory polymer is deformed at a temperature defined by a specific phase transition, the deformed shape is fixed upon cooling, but the original shape can be recovered on reheating. Here the perfluorosulphonic acid ionomer Nafion is shown to exhibit at least four different shapes as a result of its broad reversible phase transition.
The presence of gaseous chlorine atom precursors within the troposphere was thought only to occur in marine areas but now nitryl chloride has been found at a distance of 1,400 km from the nearest coastline. A model study shows that the amount of nitryl chloride production in the continental USA alone is similar to previous global estimates for marine regions. A significant fraction of tropospheric chlorine atoms may arise directly from anthropogenic pollutants.
The Red Queen hypothesis predicts that coevolution should increase the rate of evolution at the molecular level. Here, genome sequencing in an experimental phage–bacteria system is used to show that this is true, but the effect is concentrated on specific loci, and also that coevolution drives greater diversification of phage populations.
Evolution from one fitness peak to another must involve either transitions through intermediates of low fitness or skirting round the fitness valley through compensatory mutations elsewhere. Here, the base pairs in mitochondrial tRNA stems is used as a model to show that deep fitness valleys can be traversed. Transitions between AU and GC pairs have occurred during mammalian evolution without help from genetic drift or mutations elsewhere.
The existence of all-female species of whiptail lizard, formed as a hybrid between sexual species, has been known since 1962; however, how the meiotic program is altered to produce diploid eggs while maintaining heterozygosity has remained unclear. Here it is shown in parthenogenetic species that meiosis initiates with twice the number of chromosomes compared to sexual species, and that pairing and recombination takes place between genetically identical sister chromosomes instead of between homologues.
A genome-wide RNA interference screen to systematically test the genetic basis for formation and function of the Drosophila muscle is described. A role in muscle for 2,785 genes is identified; many of these genes are phylogenetically conserved.
Here, iPS cell technology is used to study the mechanisms underlying dyskeratosis congenita in humans. Reprogramming restores telomere elongation in dyskeratosis congenita cells despite genetic lesions affecting telomerase. The reprogrammed cells were able to overcome a critical limitation in telomerase RNA component (TERC) levels to restore telomere maintenance and self-renewal, and multiple telomerase components are targeted by pluripotency-associated transcription factors.
Mammals are repelled by large concentrations of salts but attracted to low concentrations of sodium. In mice, the latter behaviour can be blocked by the ion channel inhibitor amiloride. Here, mice have been produced lacking the drug's target sodium channel, ENaC, specifically in taste receptor neurons. It is confirmed that sodium sensing, like the four other taste modalities (sweet, sour, bitter and umami), is mediated by a dedicated 'labelled line'.
In a mouse model of prostate cancer it is shown that infiltrating B cells promote tumorigenesis by secreting lymphotoxin. Lymphotoxin accelerates the emergence of castration-resistant prostate tumours in this model. Interfering with this pathway may offer therapeutic strategies for androgen-independent prostate cancer.
Polycomb proteins have a key role in regulating the expression of genes essential for development, differentiation and maintenance of cell fates. Here, Polycomb repressive complex 2 (PRC2) is shown to form a complex with JARID2, a Jumonji domain protein. JARID2 is required for the binding of Polycomb proteins to target genes in embryonic stem cells as well as for the proper differentiation of ES cells.
Lidia Brito, Mozambique's former science minister, now heads the science-policy division at the United Nations Educational, Scientific and Cultural Organization (UNESCO) in Paris.
Bring together a large number of particles and they can order themselves in unusual ways. This can give rise to emergent phenomena that cannot be understood solely in terms of the interactions that rule at the microscopic level — a theoretical and experimental playground for physicists in which the maxim 'more is different' holds true in particularly striking ways.