Autoinhibition of TBCB regulates EB1-mediated microtubule dynamics

Tubulin cofactors (TBCs) participate in the folding, dimerization, and dissociation pathways of the tubulin dimer. Among them, TBCB and TBCE are two CAP-Gly domain-containing proteins that together efficiently interact with and dissociate the tubulin dimer. In the study reported here we showed that TBCB localizes at spindle and midzone microtubules during mitosis. Furthermore, the motif DEI/M-COO^? present in TBCB, which is similar to the EEY/F-COO^? element characteristic of EB proteins, CLIP-170, and α-tubulin, is required for TBCE–TBCB heterodimer formation and thus for tubulin dimer dissociation. This motif is responsible for TBCB autoinhibition, and our analysis suggests that TBCB is a monomer in solution. Mutants of TBCB lacking this motif are derepressed and induce microtubule depolymerization through an interaction with EB1 associated with microtubule tips. TBCB is also able to bind to the chaperonin complex CCT containing α-tubulin, suggesting that it could escort tubulin to facilitate its folding and dimerization, recycling or degradation.     

The Soret effect and isotopic fractionation in high-temperature silicate melts

Diffusion in condensed phases is a ubiquitous but poorly understood phenomenon. For example, chemical diffusion, which is the transport of matter associated with chemical concentration gradients (Fick's law), is treated as a separate process from thermal transport (the Soret effect), which is mass transport induced by temperature gradients. In the past few years, large variations in the proportions of isotopes of Mg, Ca, Fe, Si and O found in silicate melts subject to thermal gradients have been found, but no physical mechanism has been proposed. Here we present a model of diffusion in natural condensed systems that explains both the chemical and isotopic fractionation of Mg, Ca and Fe in high-temperature geochemical melts. Despite the high temperatures associated with these melts (T>1,000 °C), we find that consideration of the quantum-mechanical zero-point energy of diffusing species is essential for understanding diffusion at the isotopic level. Our model explains thermal and chemical mass transport as manifestations of the same underlying diffusion mechanism. This work promises to provide insights into mass-transport phenomena (diffusion and evaporation) and associated isotopic fractionations in a wide range of natural condensed systems, including the atmospheric water cycle, geological and geochemical systems and the early Solar System. This work might also be relevant to studies of mass transport in biological and nanotechnological condensed systems.     

Climbing as an escape behavior in the American hog-nosed skunk, Conepatus leuconotus

Climbing behavior is poorly documented in skunk species, with the exception of the genus Spilogale. Herein we describe 2 cases of climbing behavior in the American hog-nosed skunk ( Conepatus leuconotus ): one in Colima, Mexico, and another in west central Texas, USA. In both cases, a male climbed over 5 m into oak trees when pursued by humans. Climbing as an escape behavior in hog-nosed skunks has not previously been reported.     

Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia

Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic.     

Urban structure and the risk of influenza A (H1N1) outbreaks in municipal districts

Changsha was one of the most affected areas during the 2009 A (H1N1) influenza pandemic in China. Here, we analyze the spatial–temporal dynamics of the 2009 pandemic across Changsha municipal districts, evaluate the relationship between case incidence and the local urban spatial structure and predict high-risk areas of influenza A (H1N1). We obtained epidemiological data on all cases of influenza A (H1N1) reported across municipal districts in Changsha during period May 2009–December 2010 and data on population density and basic geographic characteristics for 239 primary schools, 97 middle schools, 347 universities, 96 malls and markets, 674 business districts and 121 hospitals. Spatial–temporal K functions, proximity models and logistic regression were used to analyze the spatial distribution pattern of influenza A (H1N1) incidence and the association between influenza A (H1N1) cases and spatial risk factors and predict the infection risks. We found that the 2009 influenza A (H1N1) was driven by a transmission wave from the center of the study area to surrounding areas and reported cases increased significantly after September 2009. We also found that the distribution of influenza A (H1N1) cases was associated with population density and the presence of nearest public places, especially universities (OR = 10.166). The final predictive risk map based on the multivariate logistic analysis showed high-risk areas concentrated in the center areas of the study area associated with high population density. Our findings support the identification of spatial risk factors and high-risk areas to guide the prioritization of preventive and mitigation efforts against future influenza pandemics.