《自然》（20190117出版）一周论文导读

▲ 作者：Minh-Son Pham、Chen Liu、Iain Todd、Jedsada Lertthanasarn 

▲ 链接：

https://www.nature.com/articles/s41586-018-0850-3

▲ 摘要：

本研究利用多向晶格，并结合3D打印技术制成一种强度增加但质量依旧较轻的人造材料。该晶格结构由重复节点和连接支柱组成，结合3D打印技术打印出来的材料既轻便又坚固。

研究人员模拟多晶材料设计了具有粒状结构的新型晶格状超材料，使内部晶格的不同区域具有不同的取向。结果显示，粒状超材料发生形变时，比传统超材料更坚固，更耐损。

与多晶材料一样，变斑晶的强度可以通过缩小每个粒状晶格区域的尺寸来增强。然而，当这些材料失效时，便是灾难性的，这限制了它们的实际应用。

▲ Abstract

Architected materials that consist of periodic arrangements of nodes and struts are lightweight and can exhibit combinations of properties (such as negative Poisson ratios) that do not occur in conventional solids. 

Architected materials reported previously are usually constructed from identical ‘unit cells’ arranged so that they all have the same orientation. As a result, when loaded beyond the yield point, localized bands of high stress emerge, causing catastrophic collapse of the mechanical strength of the material. This ‘post-yielding collapse’ is analogous to the rapid decreases in stress associated with dislocation slip in metallic single crystals. Here we use the hardening mechanisms found in crystalline materials to develop architected materials that are robust and damage-tolerant, by mimicking the microscale structure of crystalline materials—such as grain boundaries, precipitates and phases. The crystal-inspired mesoscale structures in our architected materials are as important for their mechanical properties as are crystallographic microstructures in metallic alloys. Our approach combines the hardening principles of metallurgy and architected materials, enabling the design of materials with desired properties.

▲ 作者：BenjaminD. Ravetz、AndrewB. Pun、EmilyM. Churchill、DanielN. Congreve、TomislavRovis、LuisM. Campos

▲ 链接：

https://www.nature.com/articles/s41586-018-0835-2

▲ 摘要：

近年来在光催化方面的进展使得实现各种具有挑战性的合成转化、聚合和表面修饰成为可能。所有这些反应都需要紫外线或可见光的刺激。

然而，可见光辐照的应用存在挑战。不过，一些问题可以通过使用近红外光来解决，近红外光能通过各种介质，特别是生物组织的穿透深度更深。

在此，研究人员利用三重融合上转换的光物理过程，展示了在红外辐射下的各种光氧化还原转换，并证明这是一种适用于各种光氧化反应的通用策略。

▲ Abstract

Recent advances in photo redox catalysis have made it possible to achieve various challenging synthetic transformations, polymerizations and surface modifications. All of these reactions require ultraviolet- or visible-light stimuli; however, the use of visible-light irradiation has intrinsic challenges. For example, the penetration of visible light through most reaction media is very low, leading to problems in large-scale reactions. Moreover, reactants can compete with photo catalysts for the absorption of incident light, limiting the scope of the reactions. These problems can be overcome by the use of near-infrared light, which has a much higher penetration depth through various media, notably biological tissue. Here we demonstrate various photo redox transformations under infrared radiation by utilizing the photophysical process of triplet fusion upconversion, a mechanism by which two low-energy photons are converted into a higher-energy photon. We show that this is a general strategy applicable to a wide range of photo redox reactions. We tune the upconversion components to adjust the output light, accessing both orange light and blue light from low-energy infrared light, by pairwise manipulation of the sensitizer and annihilator. We further demonstrate that the annihilator itself can be used as a photocatalyst, thus simplifying the reaction. This approach enables catalysis of high-energy transformations through several opaque barriers using low-energy infrared light.

▲ 作者：AkiraYokoyama、NobuyukiKakiuchi、SeishiOgawa，etal

▲ 链接：

https://www.nature.com/articles/s41586-018-0811-x

▲ 摘要：

在衰老的正常组织中，克隆扩展与癌症的发展有关。然而，人们对这种扩张的年代学和风险依赖性知之甚少。

在这里，研究人员对682个食管微尺度样本进行密集测序，并显示在生理正常的食管上皮细胞中，携带驱动基因（NOTCH1）突变的无性系随着年龄的增长而逐渐扩增，这一过程因饮酒和吸烟而大大加快。

随着年龄的增长，驱动突变克隆体的数量和大小逐渐增加，最终取代了极高龄患者几乎整个食管上皮细胞。

驱动基因突变克隆对食管上皮细胞的重构是正常衰老的必然结果，而正常衰老可能会影响癌症的发展，这取决于生活方式的风险。

▲ Abstract

Clonal expansion in aged normal tissues has been implicated in the development of cancer. However, the chronology and risk dependence of the expansion are poorly understood. Here we intensively sequence 682 micro-scale oesophageal samples and show, in physiologically normal oesophageal epithelia, the progressive age-related expansion of clones that carry mutations in driver genes(predominantly NOTCH1), which is substantially accelerated by alcohol consumption and by smoking. Driver-mutated clones emerge multifocally from early childhood and increase their number and size with aging, and ultimately replace almost the entire oesophageal epithelium in the extremely elderly. Compared with mutations in oesophageal cancer, there is a marked overrepresentation of NOTCH1 and PPM1D mutations in physiologically normal oesophageal epithelia; these mutations can be acquired before late adolescence (as early as early infancy) and significantly increase in number with heavy smoking and drinking. The remodelling of the oesophageal epithelium by driver-mutated clones is an inevitable consequence of normal aging, which—depending on lifestyle risks—may affect cancer development.

▲ 作者：MdMunan Shaik、HanqinPeng、JianmingLu、SophiaRits-Volloch、ChenXu、MaofuLiao、BingChen 

▲ 链接：

https://www.nature.com/articles/s41586-018-0804-9

▲ 摘要：

HIV-1包膜糖蛋白（Env）包含三聚体  (gp160)3 分裂成  (gp120 and gp41)3 ，与主要受体CD4和辅助受体（例如趋化因子受体CCR5）相互作用，融合病毒和靶细胞膜。

在本研究中，研究人员利用分辨率为3.9Å的冷冻电镜，观察到在可溶性CD4和未修饰的人CCR5复合物中gp120的结构。

研究人员还发现辅助受体可能通过稳定和锚定CD4诱导的Env在细胞膜附近的构象而发挥作用。这有助于加深对HIV-1进入宿主细胞过程的了解，为HIV药物开发提供了潜在途径。

▲ Abstract

HIV-1 envelope glycoprotein （Env）, which consists of trimeric  (gp160)3 cleaved to  (gp120 and gp41)3 , interacts with the primary receptor CD4 and a coreceptor (such as chemokine receptor CCR5) to fuse viral and target-cell membranes. The gp120–coreceptor interaction has previously been proposed as the most crucial trigger for unleashing the fusogenic potential of gp41. Here we report a cryo-electron microscopy structure of a full-length gp120 in complex with soluble CD4 and unmodified human CCR5, at 3.9 Å resolution. The V3 loop of gp120 inserts into the chemokine-binding pocket formed by seven transmembrane helices of CCR5, and the N terminus of CCR5 contacts the CD4-induced bridging sheet of gp120. CCR5induces no obvious allosteric changes in gp120 that can propagate to gp41; it does bring the Env trimer close to the target membrane. The N terminus ofgp120, which is gripped by gp41 in the pre-fusion or CD4-bound Env, flips back in the CCR5-bound conformation and may irreversibly destabilize gp41 to initiate fusion. The coreceptor probably functions by stabilizing and anchoring the CD4-induced conformation of Env near the cell membrane. These results advance our understanding of HIV-1 entry into host cells and may guide the development of vaccines and therapeutic agents.

▲ 作者：ShinnosukeHiguchi、FumiakiSugahara、WataruTakagi、YasuhiroOisi、ShigeruKuratani 

▲ 链接：

https://www.nature.com/articles/s41586-018-0782-y

▲ 摘要：

颌类脊椎动物的内耳有三个半规管，它们的存在是理解进化关系的关键。

甲青鱼只有两个半规管。七鳃鳗是现代圆口鱼，一般认为它有两个半规管，而盲鳗——也是圆口鱼——只有一个，这在过去被认为是一种更原始的特征。

然而，最近的分子和发育分析有力地支持了圆口鱼的单一性，这使得脊椎动物内耳的进化轨迹尚不清楚。

这里，研究人员展示了东亚叉牙七鳃鳗和近岸布氏黏盲鳗的耳泡分化。这些结果有助于了解圆口鱼内耳发育和脊椎动物半规管进化。

▲ Abstract

Jawed vertebrates have inner ears with three semicircular canals, the presence of which has been used as a key to understanding evolutionary relationships. Ostracoderms, the jawless stem gnathostomes, had only two canals and lacked the lateral canal. Lampreys, which are modern cyclostomes, are generally thought to possess two semicircular canals whereas the hagfishes—which are also cyclostomes—have only a single canal, which used to be regarded as a more primitive trait. However, recent molecular and developmental analyses have strongly supported the monophyly of cyclostomes, which has left the evolutionary trajectory of the vertebrate inner ear unclear. Here we show the differentiation of the otic vesicle of the lamprey Lethenteron camtschaticum and inshore hagfish Eptatretusburgeri. This is the first time, to our knowledge, that the development of the hagfish inner ear is reported. We found that canal development in the lamprey starts with two depressions—which is reminiscent of the early developmental pattern of the inner ear in modern gnathostomes. These cyclostome otic vesicles show a pattern of expression of regulatory genes, including OTX genes, that is comparable to that of gnathosomes. Although two depressions appear in the lamprey vesicle, they subsequently fuse to form a single canal that is similar to that of hagfishes. Complete separation of the depressions results in anterior and posterior canals in gnathostomes. The single depression of the vesicle in hagfishes thus appears to be a secondarily derived trait. Furthermore, the lateral canal in crown gnathostomes was acquiredsecondarily—not by de novo acquisition of an OTX expression domain, but by the evolution of a developmental program downstream of the OTX genes.

▲ 作者：ChengZhang、YiZhang、XiangYuan、AndrewC. Potter、FaxianXiu，etal 

▲ 链接：

https://www.nature.com/articles/s41586-018-0798-3

▲ 摘要：

对通电的导体加上垂直于电流方向的磁场，电子的运动轨迹将发生偏转，在导体的纵向方向产生电压,这个电磁现象就是“霍尔效应”。

但以往的实验证明，量子霍尔效应只会在二维或准二维体系中发生。本研究基于三维拓扑半金属材料Cd₃As₂，发现一种新型的量子霍尔效应，认为三维量子霍尔效应的来源于与外尔轨道。

研究人员利用楔形Cd₃As₂纳米片，发现样品厚度对量子霍尔输运产生极大的调制。这一发现为未来三维空间电子的量子化传输提供了新的思路和实验基础。

▲ Abstract

Discovered decades ago, the quantum Hall effect remains one of the most studied phenomena in condensed matter physics and is relevant for research areas such as topological phases, strong electron correlations and quantum computing. The quantized electron transport that is characteristic of the quantum Hall effect typically originates from chiral edge states—ballistic conducting channels that emerge when two-dimensional electron systems are subjected to large magnetic fields. However, whether the quantum Hall effect can be extended to higher dimensions without simply stacking two-dimensional systems is unknown. Here we report evidence of a new type of quantum Hall effect, based on Weyl orbits innano structures of the three-dimensional topological semimetal Cd₃As₂. The Weyl orbits consist of Fermi arcs (open arc-like surface states) on opposite surfaces of the sample connected by one-dimensional chiral Land aulevels along the magnetic field through the bulk. This transport through the bulk results in an additional contribution (compared to stacked two-dimension alsystems and which depends on the sample thickness) to the quantum phase of the Weyl orbit. Consequently, chiral states can emerge even in the bulk. To measure these quantum phase shifts and search for the associated chiral modes in the bulk, we conduct transport experiments using wedge-shaped Cd₃As₂ nanostructures with variable thickness. We find that the quantum Hall transport is strongly modulated by the sample thickness. The dependence of the Landau levels on the magnitude and direction of the magnetic field and on the sample thickness agrees with theoretical predictions based on the modified Lifshitz–Onsagerrelation for the Weyl orbits. Nanostructures of topological semimetals thus provide a way of exploring quantum Hall physics in three-dimensional materials with enhanced tunability.