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Science论文导读 0811

时间: 2017年08月21日 | 作者: admin | 来源: 未知
1 【生物】 Eye patches: Protein assembly of index-gradient squid lenses 眼斑:鱿鱼晶状体 中 具有折射率 梯度 的蛋白 质组装结构 A. M. Sweeney et al. http://science.sciencemag.org/content/357/6351/564 图片来源:

1【生物】Eye patches: Protein assembly of index-gradient squid lenses


A. M. Sweeney et al.








A parabolic relationship between lens radius and refractive index allows spherical lenses to avoid spherical aberration. We show that in squid, patchy colloidal physics resulted from an evolutionary radiation of globular S-crystallin proteins. Small-angle x-ray scattering experiments on lens tissue show colloidal gels of S-crystallins at all radial positions. Sparse lens materials form via low-valence linkages between disordered loops protruding from the protein surface. The loops are polydisperse and bind via a set of hydrogen bonds between disordered side chains. Peripheral lens regions with low particle valence form stable, volume-spanning gels at low density, whereas central regions with higher average valence gel at higher densities. The proteins demonstrate an evolved set of linkers for self-assembly of nanoparticles into volumetric materials.







2 【生物】Microbiota-activated PPAR-γ signaling inhibits dysbiotic Enterobacteriaceae expansion


Andreas J. Bäumler et al.








Perturbation of the gut-associated microbial community may underlie many human illnesses, but the mechanisms that maintain homeostasis are poorly understood. We found that the depletion of butyrate-producing microbes by antibiotic treatment reduced epithelial signaling through the intracellular butyrate sensor peroxisome proliferator–activated receptor (PPAR-γ). Nitrate levels increased in the colonic lumen because epithelial expression of Nos2, the gene encoding inducible nitric oxide synthase, was elevated in the absence of PPAR-γ signaling. Microbiota-induced PPAR-γ signaling also limits the luminal bioavailability of oxygen by driving the energy metabolism of colonic epithelial cells (colonocytes) toward β-oxidation. Therefore, microbiota-activated PPAR-γ signaling is a homeostatic pathway that prevents a dysbiotic expansion of potentially pathogenic Escherichia and Salmonella by reducing the bioavailability of respiratory electron acceptors to Enterobacteriaceae in the lumen of the colon.


(导读:阿金)本研究发现PPAR- γ通路维持肠道菌群稳态的关键信号通路。由肠道微生物产生的丁酸可激活肠道上皮细胞中的PPAR- γ通路使肠道中的硝酸盐和氧含量维持在低水平,从而抑制大肠杆菌和沙门氏菌等潜在致病微生物的有氧呼吸和过度增殖。这一机制为预防肠疾病提供新的思路



3【化学】Metal-catalyzed electrochemical diazidation of alkenes


Song Lin et al.



Vicinal diamines are a common structural motif in bioactive natural products, therapeutic agents, and molecular catalysts, motivating the continuing development of efficient, selective, and sustainable technologies for their preparation. We report an operationally simple and environmentally friendly protocol that converts alkenes and sodium azide—both readily available feedstocks—to 1,2-diazides. Powered by electricity and catalyzed by Earth-abundant manganese, this transformation proceeds under mild conditions and exhibits exceptional substrate generality and functional group compatibility. Using standard protocols, the resultant 1,2-diazides can be smoothly reduced to vicinal diamines in a single step, with high chemoselectivity. Mechanistic studies are consistent with metal-mediated azidyl radical transfer as the predominant pathway, enabling dual carbon-nitrogen bond formation.


(导读 卓思琪)邻二胺存在普遍且用途广泛。本研究利用烯烃和叠氮化钠制备1,2-二叠氮化合物。该过程通过电力驱动,并在锰的催化下进行,其反应条件温和,兼容性适应性广泛。使用常规方法,1,2-二叠氮能化学选择性地一步还原为邻二胺。机理分析表明金属介导的叠氮基自由基转移可以实现双重碳-氮键的形成,为反应主要途径。


4【地球科学】A unified continental thickness from seismology and diamonds suggests a melt-defined plate



Saikiran Tharimena et al.






Thick, rigid continents move over the weaker underlying mantle, although geophysical and geochemical constraints on the exact thickness and defining mechanism of the continental plates are widely discrepant. Xenoliths suggest a chemical continental lithosphere ~175 kilometers thick, whereas seismic tomography supports a much thicker root (>250 kilometers) and a gradual lithosphere-asthenosphere transition, consistent with a thermal definition. We modeled SS precursor waveforms from continental interiors and found a 7 to 9% velocity drop at depths of 130 to 190 kilometers. The discontinuity depth is well correlated with the origin depths of diamond-bearing xenoliths and corresponds to the transition from coarse to deformed xenoliths. At this depth, the xenolith-derived geotherm also intersects the carbonate-silicate solidus, suggesting that partial melt defines the plate boundaries beneath the continental interior.




5【经济】The dual frontier: Patented inventions and prior scientific advance


Benjamin F. Jones et al.



The extent to which scientific advances support marketplace inventions is largely unknown. We study 4.8 million U.S. patents and 32 million research articles to determine the minimum citation distance between patented inventions and prior scientific advances. We find that most cited research articles (80%) link forward to a future patent. Similarly, most patents (61%) link backward to a prior research article. Linked papers and patents typically stand 2 to 4 degrees distant from the other domain. Yet, advances directly along the patent-paper boundary are notably more impactful within their own domains. The distance metric further provides a typology of the fields, institutions, and individuals involved in science-to-technology linkages. Overall, the findings are consistent with theories that emphasize substantial and fruitful connections between patenting and prior scientific inquiry.


导读 陈月欣 目前人们对于前沿科学的进展对市场发明的推动支持程度尚不了解。本研究对480万份美国专利和3200万篇科学论文对比后发现,专利技术发明与前沿科学发表存在着紧密的联系,大部分学术论文都会导致后续的专利发明,而专利都可追溯到对应的论文。其中,生物医学、计算机科学和工程学等学科的学界-业界联系尤为密切。


6【地球科学】Changing climate shifts timing of European floods


Günter Blöschl et al.






A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.


(导读 阿金)气候变暖会影响洪水爆发的时间和量级。本研究分析了来自欧洲4262个水文站近50年来的洪水数据,发现在欧洲各个地区,气温升高、极地变暖以及土壤湿度增加会影响冰雪融化以及冬季洪水到来的时间。研究结果证实了通过观察欧洲洪水数据可发现明显的气候变化信号。


7【生物】Two areas for familiar face recognition in the primate brain




Sofia M. Landi and Winrich A. Freiwald




Familiarity alters face recognition: Familiar faces are recognized more accurately than unfamiliar ones and under difficult viewing conditions when unfamiliar face recognition fails. The neural basis for this fundamental difference remains unknown. Using whole-brain functional magnetic resonance imaging, we found that personally familiar faces engage the macaque face-processing network more than unfamiliar faces. Familiar faces also recruited two hitherto unknown face areas at anatomically conserved locations within the perirhinal cortex and the temporal pole. These two areas, but not the core face-processing network, responded to familiar faces emerging from a blur with a characteristic nonlinear surge, akin to the abruptness of familiar face recognition. In contrast, responses to unfamiliar faces and objects remained linear. Thus, two temporal lobe areas extend the core face-processing network into a familiar face-recognition system.


(导读 董堃)熟悉的面孔总是更容易辨认,但此现象的神经基础未知。研究人员通过全脑功能性核磁共振扫描恒河猴的脑区发现,当熟悉的面孔突然靠近时,两个在面孔识别网络中并非占主导地位的脑区,边缘皮层和颞极,会作出非线性反应迅速激活,说明了这两个颞叶脑区处理熟悉面孔重要作用


8【生物】Pavlovian conditioninginduced hallucinations result from overweighting of perceptual priors


P. R. Corlett et al.


Some people hear voices that others do not, but only some of those people seek treatment. Using a Pavlovian learning task, we induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, we identified processes that differentiated voice-hearers from non–voice-hearers and treatment-seekers from non–treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations. These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without.


【导读 陈月欣】 有些人存在幻听,会在脑中听到其他人听不见的声音。本研究采用巴浦洛夫式习得性任务,在有/没有幻听和接受/未接受治疗的4组被试者中建立了条件诱导性的幻觉,其中有幻听的受试者更容易被诱导。研究还借助功能性神经成像鉴别出与这一幻听过程相关的脑神经回路,为基础和临床提供帮助。


9【生物】Single-cell methylomes identify neuronal subtypes and regulatory elements in mammalian cortex


Eran A. Mukamel, M. Margarita Behrens, Joseph R. Ecker et al.




The mammalian brain contains diverse neuronal types, yet we lack single-cell epigenomic assays that are able to identify and characterize them. DNA methylation is a stable epigenetic mark that distinguishes cell types and marks regulatory elements. We generated >6000 methylomes from single neuronal nuclei and used them to identify 16 mouse and 21 human neuronal subpopulations in the frontal cortex. CG and non-CG methylation exhibited cell type–specific distributions, and we identified regulatory elements with differential methylation across neuron types. Methylation signatures identified a layer 6 excitatory neuron subtype and a unique human parvalbumin-expressing inhibitory neuron subtype. We observed stronger cross-species conservation of regulatory elements in inhibitory neurons than in excitatory neurons. Single-nucleus methylomes expand the atlas of brain cell types and identify regulatory elements that drive conserved brain cell diversity.



(导读 郭怿暄)哺乳动物大脑中神经细胞多种多样,至今仍缺乏有效的区分手段。本研究生成了超过6千个单个神经细胞的甲基化组,发现通过CG和非CG甲基化的细胞特异性分布以及调控序列甲基化水平的差异性可以鉴别不同神经细胞亚群。调控序列在不同物种的抑制性神经元中具有保守性。这一发现扩展了当前的大脑细胞图谱。



10 【生物】A cyclic oligonucleotide signaling pathway in type III CRISPR-Cas systems

III CRISPR-Cas 系统中的环核苷酸信号通路

Gintautas Tamulaitis, Virginijus Siksnys et al.



Type III CRISPR-Cas systems in prokaryotes provide immunity against invading nucleic acids through the coordinated degradation of transcriptionally active DNA and its transcripts by the Csm effector complex. The Cas10 subunit of the complex contains an HD nuclease domain that is responsible for DNA degradation and two Palm domains with elusive functions. In addition, Csm6, a ribonuclease that is not part of the complex, is also required to provide full immunity. We show here that target RNA binding by the Csm effector complex of Streptococcus thermophilus triggers Cas10 to synthesize cyclic oligoadenylates (cAn; n = 2 to 6) by means of the Palm domains. Acting as signaling molecules, cyclic oligoadenylates bind Csm6 to activate its nonspecific RNA degradation. This cyclic oligoadenylate–based signaling pathway coordinates different components of CRISPR-Cas to prevent phage infection and propagation.


(导读 郭怿暄)原核生物中IIICRISPR-Cas系统可通过降解转录活跃的外源入侵DNA及其RNA产物为细菌提供保护。本研究发现嗜热链球菌中Csm效应复合物与靶RNA的结合可促使Cas10合成第二信使环形寡腺苷酸,这一信号分子与Csm6结合并激活其非特异性RNA降解功能,从而降解靶RNA,保护细菌免遭噬菌体感染和增殖。




11 【生物】Structure of histone-based chromatin in Archaea


Karolin Luger et al.



Small basic proteins present in most Archaea share a common ancestor with the eukaryotic core histones. We report the crystal structure of an archaeal histone-DNA complex. DNA wraps around an extended polymer, formed by archaeal histone homodimers, in a quasi-continuous superhelix with the same geometry as DNA in the eukaryotic nucleosome. Substitutions of a conserved glycine at the interface of adjacent protein layers destabilize archaeal chromatin, reduce growth rate, and impair transcription regulation, confirming the biological importance of the polymeric structure. Our data establish that the histone-based mechanism of DNA compaction predates the nucleosome, illuminating the origin of the nucleosome.


(导读 郭怿暄)真核细胞中,DNA围绕组蛋白八聚体形成的核小体是染色质结构的基本单位。本研究解析了古细菌中组蛋白-DNA复合体的晶体结构,发现其几何构型与真核细胞核小体一致。这一结果为核小体的起源与进化提供了强有力的证据。