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Science论文导读 1110

时间: 2017年11月20日 | 作者: admin | 来源: 未知
Science 20171110 1 【化学】 Lewis acid enhancement by hydrogen-bond donors for asymmetric catalysis Steven M. Banik and Anna Levina et.al 由 氢键供体 强化的 路易斯酸 可用于 非对称催化 http://science.sciencemag.org/co

Science 20171110

 

1【化学】Lewis acid enhancement by hydrogen-bond donors for asymmetric catalysis

Steven M. Banik and Anna Levina et.al

 

氢键供体强化的路易斯酸可用于非对称催化

 

http://science.sciencemag.org/content/358/6364/761

图片3.png 

(导读 阿金)小分子双氢键供体可作为对映选择性反应的催化剂。但其仅具有弱酸性,故仅对高活性的亲电底物有效。本研究介绍一种对于较低活性底物有效的催化模式:即用氢键供体方酰胺与路易斯酸三氟甲磺酸结合,形成稳定的高酸性催化复合物,该手性复合物可催化相对不活泼的亲电体实现对映选择性反应。

 

Small-molecule dual hydrogen-bond (H-bond) donors such as ureas, thioureas, squaramides, and guanidinium ions enjoy widespread use as effective catalysts for promoting a variety of enantioselective reactions. However, these catalysts are only weakly acidic and therefore require highly reactive electrophilic substrates to be effective. We introduce here a mode of catalytic activity with chiral H-bond donors that enables enantioselective reactions of relatively unreactive electrophiles. Squaramides are shown to interact with silyl triflates by binding the triflate counterion to form a stable, yet highly Lewis acidic, complex. The silyl triflate-chiral squaramide combination promotes the generation of oxocarbenium intermediates from acetal substrates at low temperatures. Enantioselectivity in nucleophile additions to the cationic intermediates is then controlled through a network of noncovalent interactions between the squaramide catalyst and the oxocarbenium triflate.

 

2 【物理】Observation of mean path length invariance in light-scattering media

在光散射媒介中观测平均光程的不变性

http://science.sciencemag.org/content/358/6364/765

Sylvain Gigan,el at.

 

The microstructure of a medium strongly influences how light propagates through it. The amount of disorder it contains determines whether the medium is transparent or opaque. Theory predicts that exciting such a medium homogeneously and isotropically makes some of its optical properties depend only on the medium’s outer geometry. Here, we report an optical experiment demonstrating that the mean path length of light is invariant with respect to the microstructure of the medium it scatters through. Using colloidal solutions with varying concentration and particle size, the invariance of the mean path length is observed over nearly two orders of magnitude in scattering strength. Our results can be extended to a wide range of systems—however ordered, correlated, or disordered—and apply to all wave-scattering problems.

 

(导读 葛鹏)介质的微观结构影响着光在其中的传播方式。理论预测当激发是均匀且各向同性时,介质部分光学属性仅取决于外部几何结构。本研究通过实验证明了平均光程对光散射介质微观结构具有不变性。这一结果可以被广泛的应用于有序、相关和无序的系统中,同时可以用于解决与波散射相关的问题。

 

 

3 【材料】Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%

Neha Arora and M. Ibrahim Dar et.al

具有 CuSCN 空穴提取层的钙钛矿太阳能电池能达到> 20%的稳定转换效率

http://science.sciencemag.org/content/358/6364/768

(导读 阿金)效率高于20%的钙钛矿太阳能电池(PSC)只能通过昂贵的有机空穴传输材料才能实现。本研究利用硫氰酸铜(CuSCN)制成紧凑且高度共形的空穴提取层,在CuSCN和金之间添加导电性还原氧化石墨烯间隔层,使得PSC60摄氏度最大输出功率点运转1000小时后仍保持95%的初始效率。

Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized only with expensive organic hole-transporting materials. We demonstrate PSCs that achieve stabilized efficiencies exceeding 20% with copper(I) thiocyanate (CuSCN) as the hole extraction layer. A fast solvent removal method enabled the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The PSCs showed high thermal stability under long-term heating, although their operational stability was poor. This instability originated from potential-induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours under full solar intensity at 60°C. Under both continuous full-sun illumination and thermal stress, CuSCN-based devices surpassed the stability of spiro-OMeTAD–based PSCs.

 

 

4 物理Distinguishing a Majorana zero mode using spin-resolved measurements

Sangjun Jeon, Yonglong Xie and Jian Li et.al

用自旋分辨测量来区分马约拉那费米子能模式(MZMs

(导读 阿金)具有MZMs一维拓扑超导体的非局域性可应用于量子计算。本研究使用自旋极化扫描隧道显微镜,展示了在铅表面上自组装铁链的MZMs的自旋极化超过源自磁性产生的自旋极化,并指出这是拓扑带结构产生的MZMs希尔伯特空间非局域性的直接结果。研究结果表明利用自旋极化测量可区分超导体的常规带隙内能态和拓扑MZMs

http://science.sciencemag.org/content/358/6364/772

One-dimensional topological superconductors host Majorana zero modes (MZMs), the nonlocal property of which could be exploited for quantum computing applications. We use spin-polarized scanning tunneling microscopy to show that MZMs realized in self-assembled Fe chains on the surface of Pb have a spin polarization that exceeds that stemming from the magnetism of these chains. This feature, captured by our model calculations, is a direct consequence of the nonlocality of the Hilbert space of MZMs emerging from a topological band structure. Our study establishes spin-polarization measurements as a diagnostic tool to distinguish topological MZMs from trivial in-gap states of a superconductor.

 

 

5 【社会科学】How the news media activate public expression and influence national agendas

Gary King et.al

 

新闻媒体如何激发公众表达和影响国家议程

 

http://science.sciencemag.org/content/358/6364/776

 

 

We demonstrate that exposure to the news media causes Americans to take public stands on specific issues, join national policy conversations, and express themselves publicly—all key components of democratic politics—more often than they would otherwise. After recruiting 48 mostly small media outlets, we chose groups of these outlets to write and publish articles on subjects we approved, on dates we randomly assigned. We estimated the causal effect on proximal measures, such as website pageviews and Twitter discussion of the articles’ specific subjects, and distal ones, such as national Twitter conversation in broad policy areas. Our intervention increased discussion in each broad policy area by ~62.7% (relative to a day’s volume), accounting for 13,166 additional posts over the treatment week, with similar effects across population subgroups.

 

(导读 郭怿暄)民主政治的关键包括人民公开面对特定问题、参与政治讨论和开表达个人政治观点。本研究召集48个小型媒体在随机选定日期撰写并发布指定主题的文章,通过测量对文章话题的网页浏览量、推特讨论量以及细节信息,发现新闻发布后广泛政治领域讨论量增加62.7%,证明新闻媒体促进公众政治意愿表达。

 

6 【地球科学】Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination

B. Menounos et.al

科迪勒冰盖(CIS)融化早于更新世末期的气候突变

http://science.sciencemag.org/content/358/6364/781

(导读 阿金)过去的地质证据和数据模型显示CIS1.25万年前曾覆盖加拿大最西端大部分地区。本研究的新数据则表明,早在1.25万年甚至1.4万年前该地区已无冰层覆盖。CIS质量在Bølling-Allerød温暖期的500年内减半,导致海平面上升2.53米。到新仙女木期时冰斗和山谷冰川连同CIS南缘已成为冰川消融区。

The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas.

 

7  【生物】Genomic history of the seventh pandemic of cholera in Africa

François-Xavier Weill et.al

非洲第七次霍乱流行的基因组历史

http://science.sciencemag.org/content/358/6364/785

(导读 严冰)第七次霍乱大流行沉重地打击了非洲。本文报导,通过分析1070株来自45个非洲国家、影响历时49年的霍乱弧菌O1分离菌的遗传数据,发现第七次霍乱流行是由单个霍乱弧菌种系引起的——该种系自1970年起至少被引入西非和东南非地区11次,持续引起霍乱流行28年之久。最后的5次引入均来自亚洲,包括2000后替代了抗生素敏感亚型的多重抗药性亚型。该研究为今后非洲霍乱的防控措施设计提供了依据。

The seventh cholera pandemic has heavily affected Africa, although the origin and continental spread of the disease remain undefined. We used genomic data from 1070 Vibrio cholerae O1 isolates, across 45 African countries and over a 49-year period, to show that past epidemics were attributable to a single expanded lineage. This lineage was introduced at least 11 times since 1970, into two main regions, West Africa and East/Southern Africa, causing epidemics that lasted up to 28 years. The last five introductions into Africa, all from Asia, involved multidrug-resistant sublineages that replaced antibiotic-susceptible sublineages after 2000. This phylogenetic framework describes the periodicity of lineage introduction and the stable routes of cholera spread, which should inform the rational design of control measures for cholera in Africa.

 

8 【生物】Integrated view of Vibrio cholerae in the Americas

Daryl Domman et.al

关于美洲霍乱弧菌的综合观点

http://science.sciencemag.org/content/358/6364/789

(导读 严冰)拉丁美洲分别在1991年和2010年经历过两次霍乱流行,然而全球流行的霍乱弧菌克隆与当地细菌种群之间的关系仍不清楚。本文通过全基因组测序技术对在美洲40年中出现的霍乱进行考察,发现这两次霍乱流行都是由第七次大流行埃尔托(El Tor)生物型霍乱弧菌引起的,通过洲际间传播被引入南美洲,而当地的至少7个种系与引发不同于流行性霍乱的疾病特征相关。

 

Latin America has experienced two of the largest cholera epidemics in modern history; one in 1991 and the other in 2010. However, confusion still surrounds the relationships between globally circulating pandemic Vibrio cholerae clones and local bacterial populations. We used whole-genome sequencing to characterize cholera across the Americas over a 40-year time span. We found that both epidemics were the result of intercontinental introductions of seventh pandemic El Tor V. cholerae and that at least seven lineages local to the Americas are associated with disease that differs epidemiologically from epidemic cholera. Our results consolidate historical accounts of pandemic cholera with data to show the importance of local lineages, presenting an integrated view of cholera that is important to the design of future disease control strategies.

 

9 【神经】A neural algorithm for a fundamental computing problem

Sanjoy Dasgupta et.al

 

针对一种基本计算问题的神经算法

 

http://science.sciencemag.org/content/358/6364/793

 

 

Similarity search—for example, identifying similar images in a database or similar documents on the web—is a fundamental computing problem faced by large-scale information retrieval systems. We discovered that the fruit fly olfactory circuit solves this problem with a variant of a computer science algorithm (called locality-sensitive hashing). The fly circuit assigns similar neural activity patterns to similar odors, so that behaviors learned from one odor can be applied when a similar odor is experienced. The fly algorithm, however, uses three computational strategies that depart from traditional approaches. These strategies can be translated to improve the performance of computational similarity searches. This perspective helps illuminate the logic supporting an important sensory function and provides a conceptually new algorithm for solving a fundamental computational problem.

 

(导读 郭怿暄)相似性搜索,即从数据库中搜索出相似的图像或文件,是大规模数据检索系统中的最基本计算问题。本研究发现果蝇的嗅觉环路对相近的嗅觉产生相近的神经活动模式,可将一种味觉习得的行为应用于接触相似味觉时。研究者将其中的三种全新计算策略应用于计算领域,提出局部敏感哈希算法,该方法可有效改善近似检索时的计算表现。

 

10 【生物】Redox-sensitive alteration of replisome architecture safeguards genome integrity

Kumar Somyajit et.al

 

氧化还原敏感的复制体结构改变保护基因组的完整性

 

http://science.sciencemag.org/content/358/6364/797

 

 

DNA replication requires coordination between replication fork progression and deoxynucleotide triphosphate (dNTP)–generating metabolic pathways. We find that perturbation of ribonucleotide reductase (RNR) in humans elevates reactive oxygen species (ROS) that are detected by peroxiredoxin 2 (PRDX2). In the oligomeric state, PRDX2 forms a replisome-associated ROS sensor, which binds the fork accelerator TIMELESS when exposed to low levels of ROS. Elevated ROS levels generated by RNR attenuation disrupt oligomerized PRDX2 to smaller subunits, whose dissociation from chromatin enforces the displacement of TIMELESS from the replisome. This process instantly slows replication fork progression, which mitigates pathological consequences of replication stress. Thus, redox signaling couples fluctuations of dNTP biogenesis with replisome activity to reduce stress during genome duplication. We propose that cancer cells exploit this pathway to increase their adaptability to adverse metabolic conditions.

 

(导读 郭怿暄)DNA复制需要协调复制叉的前进速度和原料dNTP的生成速度。本研究发现在ROS水平低时,多聚化PRDX2可作为ROS感受器与复制体上的复制叉加速因子TIMELESS结合。核苷酸还原酶减弱,即dNTP合成减弱,会导致ROS上升,多聚化PRDX2感受ROS上升而解聚,并导致TIMELESS从复制体脱离,复制叉前进减速以减轻复制压力。

 

 

11 【生物】Calibrated mitotic oscillator drives motile ciliogenesis

Adel Al Jord et.al

经校准的有丝分裂振荡器驱动能动纤毛生成

http://science.sciencemag.org/content/358/6364/803

(导读:阿金)以CDK1-APC / C为中心的有丝分裂振荡器可调控细胞分裂过程中细胞器重组的时空节律,本研究发现该振荡器亦可调控非分裂细胞中与分化相关的亚细胞结构重组。小鼠多纤毛脑细胞分化过程中的中心粒扩增及纤毛生成过程是由经校正,不会引发细胞分裂的CDK1-APC / C振荡器调节发生的。

 

 

Cell division and differentiation depend on massive and rapid organelle remodeling. The mitotic oscillator, centered on the cyclin-dependent kinase 1–anaphase-promoting complex/cyclosome (CDK1-APC/C) axis, spatiotemporally coordinates this reorganization in dividing cells. Here we discovered that nondividing cells could also implement this mitotic clocklike regulatory circuit to orchestrate subcellular reorganization associated with differentiation. We probed centriole amplification in differentiating mouse-brain multiciliated cells. These postmitotic progenitors fine-tuned mitotic oscillator activity to drive the orderly progression of centriole production, maturation, and motile ciliation while avoiding the mitosis commitment threshold. Insufficient CDK1 activity hindered differentiation, whereas excessive activity accelerated differentiation yet drove postmitotic progenitors into mitosis. Thus, postmitotic cells can redeploy and calibrate the mitotic oscillator to uncouple cytoplasmic from nuclear dynamics for organelle remodeling associated with differentiation.

 

 

12 【生物】Lysosomal metabolomics reveals V-ATPase- and mTOR-dependent regulation of amino acid efflux from lysosomes

Monther Abu-Remaileh and  Gregory A. Wyant et.al

 

溶酶体代谢组学显示溶酶体氨基酸外排的调节依赖于V-ATP酶和mTOR通路

 

http://science.sciencemag.org/content/358/6364/807

 

(导读 卓思琪)本文开发了快速分离溶酶体的方法并对不同细胞状态下的溶酶体进行了代谢物定量。营养充足时抑制V-ATPase会增加溶酶体内大多数代谢产物的浓度,必需氨基酸除外。而在营养不足时,mTOR通路的抑制会减少溶酶体必要氨基酸外流从而将溶酶体作为氨基酸的储存点。这表明存在与V-ATP酶和mTOR有关的控制溶酶体氨基酸外流和代谢产物动态调控的机制。

 

The lysosome degrades and recycles macromolecules, signals to the cytosol and nucleus, and is implicated in many diseases. Here, we describe a method for the rapid isolation of mammalian lysosomes and use it to quantitatively profile lysosomal metabolites under various cell states. Under nutrient-replete conditions, many lysosomal amino acids are in rapid exchange with those in the cytosol. Loss of lysosomal acidification through inhibition of the vacuolar H+adenosine triphosphatase (V-ATPase) increased the luminal concentrations of most metabolites but had no effect on those of the majority of essential amino acids. Instead, nutrient starvation regulates the lysosomal concentrations of these amino acids, an effect we traced to regulation of the mechanistic target of rapamycin (mTOR) pathway. Inhibition of mTOR strongly reduced the lysosomal efflux of most essential amino acids, converting the lysosome into a cellular depot for them. These results reveal the dynamic nature of lysosomal metabolites and that V-ATPase- and mTOR-dependent mechanisms exist for controlling lysosomal amino acid efflux.

 

13【生物】SAMTOR is an S-adenosylmethionine sensor for the mTORC1 pathway

Xin Gu and Jose M. Orozco et.al

 

SAMTORmTORC1途径中S-腺苷甲硫氨酸的传感器

 

http://science.sciencemag.org/content/358/6364/813

 

 

(导读 卓思琪)mTOR(mTORC1)复合物通过调节细胞生长和代谢来应对环境中的多种变化。本文发现名为SAMTOR的蛋白质可以和GATOR1相互作用来抑制mTORC1信号。S-腺苷甲硫氨酸(SAM)通过和SAMTOR直接结合破坏SAMTOR-GATOR1复合物。蛋氨酸导致SAM水平降低,从而促进SAMTORGATOR1的结合抑制mTORC1信号通路。因此SAMTOR是一种SAM的传感器,将蛋氨酸与mTORC1信号联系起来。

 

mTOR complex 1 (mTORC1) regulates cell growth and metabolism in response to multiple environmental cues. Nutrients signal via the Rag guanosine triphosphatases (GTPases) to promote the localization of mTORC1 to the lysosomal surface, its site of activation. We identified SAMTOR, a previously uncharacterized protein, which inhibits mTORC1 signaling by interacting with GATOR1, the GTPase activating protein (GAP) for RagA/B. We found that the methyl donor S-adenosylmethionine (SAM) disrupts the SAMTOR-GATOR1 complex by binding directly to SAMTOR with a dissociation constant of approximately 7 μM. In cells, methionine starvation reduces SAM levels below this dissociation constant and promotes the association of SAMTOR with GATOR1, thereby inhibiting mTORC1 signaling in a SAMTOR-dependent fashion. Methionine-induced activation of mTORC1 requires the SAM binding capacity of SAMTOR. Thus, SAMTOR is a SAM sensor that links methionine and one-carbon metabolism to mTORC1 signaling.