Electron tomography at 2.4-ångström resolution

Transmission electron microscopy is a powerful imaging tool that has found broad application in materials science, nanoscience and biology. With the introduction of aberration-corrected electron lenses, both the spatial resolution and the image quality in transmission electron microscopy have been significantly improved and resolution below 0.5??ngstr?ms has been demonstrated. To reveal the three-dimensional (3D) structure of thin samples, electron tomography is the method of choice, with cubic-nanometre resolution currently achievable. Discrete tomography has recently been used to generate a 3D atomic reconstruction of a silver nanoparticle two to three nanometres in diameter, but this statistical method assumes prior knowledge of the particle's lattice structure and requires that the atoms fit rigidly on that lattice. Here we report the experimental demonstration of a general electron tomography method that achieves atomic-scale resolution without initial assumptions about the sample structure. By combining a novel projection alignment and tomographic reconstruction method with scanning transmission electron microscopy, we have determined the 3D structure of an approximately ten-nanometre gold nanoparticle at 2.4-?ngstr?m resolution. Although we cannot definitively locate all of the atoms inside the nanoparticle, individual atoms are observed in some regions of the particle and several grains are identified in three dimensions. The 3D surface morphology and internal lattice structure revealed are consistent with a distorted icosahedral multiply twinned particle. We anticipate that this general method can be applied not only to determine the 3D structure of nanomaterials at atomic-scale resolution, but also to improve the spatial resolution and image quality in other tomography fields.     

Silent spread of H5N1 in vaccinated poultry

International debate on the merits of vaccinating poultry against the H5N1 influenza A virus has raised concerns about the possibility of an increased risk of between-flock transmission before outbreaks are detected. Here we show that this 'silent spread' can occur because of incomplete protection at the flock level, even if a vaccine is effective in individual birds. The use of unvaccinated sentinels can mitigate, although not completely eliminate, the problem.     

Lunar activity from recent gas release

Samples of material returned from the Moon have established that widespread lunar volcanism ceased about 3.2 Gyr ago. Crater statistics and degradation models indicate that last-gasp eruptions of thin basalt flows continued until less than 1.0 Gyr ago, but the Moon is now considered to be unaffected by internal processes today, other than weak tidally driven moonquakes and young fault systems. It is therefore widely assumed that only impact craters have reshaped the lunar landscape over the past billion years. Here we report that patches of the lunar regolith in the Ina structure were recently removed. The preservation state of relief, the number of superimposed small craters, and the 'freshness' (spectral maturity) of the regolith together indicate that features within this structure must be as young as 10 Myr, and perhaps are still forming today. We propose that these features result from recent, episodic out-gassing from deep within the Moon. Such out-gassing probably contributed to the radiogenic gases detected during past lunar missions. Future monitoring (including Earth-based observations) should reveal the composition of the gas, yielding important clues to volatiles archived at great depth over the past 4-4.5 Gyr.     

Clarifying the mechanics of DNA strand exchange in meiotic recombination

During meiosis, accurate separation of maternal and paternal chromosomes requires that they first be connected to one another through homologous recombination. Meiotic recombination has many intriguing but poorly understood features that distinguish it from recombination in mitotically dividing cells, and several of these features depend on the meiosis-specific DNA strand exchange protein Dmc1 (disrupted meiotic cDNA1). Many questions about this protein have arisen since its discovery more than a decade ago, but recent genetic and biochemical breakthroughs promise to shed light on the unique behaviours and functions of this central player in the remarkable chromosome dynamics of meiosis.     

Description of the aberrant Leptopilina lasallei n. sp., with an updated phylogeny of Leptopilina Förster (Hymenoptera: Figitidae: Eucoilinae)

ABSTRACT

In the search for native Asian parasitoids of Drosophila suzukii, the notorious spotted-wing Drosophila (SWD), an odd new species of Eucoilinae was discovered. Leptopilina lasallei sp. nov. is herein described and diagnosed relative to other eucoilines associated with drosophilid hosts. Morphologically, L. lasallei is somewhat aberrant within Leptopilina; phylogenetically, L. lasallei is sister group to the core Leptopilina. In the process of investigating L. lasallei, a de novo molecular phylogeny of Leptopilina was generated and is included here. The integrated approach used for the characterisation of L. lasallei, and the resulting phylogeny of Leptopilina, produced data useful to select parasitoid species for SWD biological control.http://www.zoobank.org/urn:lsid:zoobank.org:act:402D504A-4616-4524-85D7-1C13A6276F06 http://www.zoobank.org/urn:lsid:zoobank.org:act:402D504A-4616-4524-85D7-1C13A6276F06     

iASPP oncoprotein is a key inhibitor of p53 conserved from worm to human

We have previously shown that ASPP1 and ASPP2 are specific activators of p53; one mechanism by which wild-type p53 is tolerated in human breast carcinomas is through loss of ASPP activity. We have further shown that 53BP2, which corresponds to a C-terminal fragment of ASPP2, acts as a dominant negative inhibitor of p53 (ref. 1). Hence, an inhibitory form of ASPP resembling 53BP2 could allow cells to bypass the tumor-suppressor functions of p53 and the ASPP proteins. Here, we characterize such a protein, iASPP (inhibitory member of the ASPP family), encoded by PPP1R13L in humans and ape-1 in Caenorhabditis elegans. iASPP is an evolutionarily conserved inhibitor of p53; inhibition of iASPP by RNA-mediated interference or antisense RNA in C. elegans or human cells, respectively, induces p53-dependent apoptosis. Moreover, iASPP is an oncoprotein that cooperates with Ras, E1A and E7, but not mutant p53, to transform cells in vitro. Increased expression of iASPP also confers resistance to ultraviolet radiation and to cisplatin-induced apoptosis. iASPP expression is upregulated in human breast carcinomas expressing wild-type p53 and normal levels of ASPP. Inhibition of iASPP could provide an important new strategy for treating tumors expressing wild-type p53.     

DNA发现之前的基因——遗传学家是如何揭示生命结构单元之基础的

原文载于《Discover》杂志2015年9月刊,摘选自马修·科布(Matthew Cobb)的著作《生命最大的秘密:角逐遗传密码真相的故事》(Life’s Greatest Secret:The Race to Crack the Genetic Code),该书于2015年7月由Basic Books出版。本文由张钫、史晓雷翻译。