《自然》（20190117出版）一周論文導讀

知識 01-21

翻譯 | 唐一塵

Nature, 17 January 2019, Volume 565 Issue 7739

《自然》2019年1月17日第7739期565卷

《自然》（20190117出版）一周論文導讀

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材料/化學

Materials/Chemistry

Damage-tolerant architected materials inspired by crystal microstructure

受晶體微結構啟發設計的耐損傷材料

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

鏈接：

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

摘要：

本研究利用多向晶格，並結合3D列印技術製成一種強度增加但質量依舊較輕的人造材料。該晶格結構由重複節點和連接支柱組成，結合3D列印技術列印出來的材料既輕便又堅固。

研究人員模擬多晶材料設計了具有粒狀結構的新型晶格狀超材料，使內部晶格的不同區域具有不同的取向。結果顯示，粒狀超材料發生形變時，比傳統超材料更堅固，更耐損。

與多晶材料一樣，變斑晶的強度可以通過縮小每個粒狀晶格區域的尺寸來增強。然而，當這些材料失效時，便是災難性的，這限制了它們的實際應用。

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.

Photoredox catalysisusing infraredlight via triplet fusion upconversion

利用紅外光通過三重融合上轉換進行光催化

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

鏈接：

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

摘要：

近年來在光催化方面的進展使得實現各種具有挑戰性的合成轉化、聚合和表面修飾成為可能。所有這些反應都需要紫外線或可見光的刺激。

然而，可見光輻照的應用存在挑戰。不過，一些問題可以通過使用近紅外光來解決，近紅外光能通過各種介質，特別是生物組織的穿透深度更深。

在此，研究人員利用三重融合上轉換的光物理過程，展示了在紅外輻射下的各種光氧化還原轉換，並證明這是一種適用於各種光氧化反應的通用策略。

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.

生物Biology

Age-related remodelling of oesophageal epithelia by mutated cancer drivers

癌症驅動因子突變引起的食管上皮細胞年齡相關性重構

作者：AkiraYokoyama、NobuyukiKakiuchi、SeishiOgawa，etal

鏈接：

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

摘要：

在衰老的正常組織中，克隆擴展與癌症的發展有關。然而，人們對這種擴張的年代學和風險依賴性知之甚少。

在這裡，研究人員對682個食管微尺度樣本進行密集測序，並顯示在生理正常的食管上皮細胞中，攜帶驅動基因（NOTCH1）突變的無性系隨著年齡的增長而逐漸擴增，這一過程因飲酒和吸煙而大大加快。

隨著年齡的增長，驅動突變克隆體的數量和大小逐漸增加，最終取代了極高齡患者幾乎整個食管上皮細胞。

驅動基因突變克隆對食管上皮細胞的重構是正常衰老的必然結果，而正常衰老可能會影響癌症的發展，這取決於生活方式的風險。

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.

Structural basisof coreceptor recognition by HIV-1 envelope spike

HIV-1包膜糖蛋白識別輔助受體的結構基礎

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

鏈接：

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

摘要：

HIV-1包膜糖蛋白（Env）包含三聚體 (gp160)3 分裂成 (gp120 and gp41)3 ，與主要受體CD4和輔助受體（例如趨化因子受體CCR5）相互作用，融合病毒和靶細胞膜。

在本研究中，研究人員利用解析度為3.9?的冷凍電鏡，觀察到在可溶性CD4和未修飾的人CCR5複合物中gp120的結構。

研究人員還發現輔助受體可能通過穩定和錨定CD4誘導的Env在細胞膜附近的構象而發揮作用。這有助於加深對HIV-1進入宿主細胞過程的了解，為HIV藥物開發提供了潛在途徑。

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 ? 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.

Inner ear developmentin cyclostomesand evolution of the vertebrate semicircular canals

圓口魚內耳發育和脊椎動物半規管進化

作者：ShinnosukeHiguchi、FumiakiSugahara、WataruTakagi、YasuhiroOisi、ShigeruKuratani

鏈接：

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

摘要：

頜類脊椎動物的內耳有三個半規管，它們的存在是理解進化關係的關鍵。

甲青魚只有兩個半規管。七鰓鰻是現代圓口魚，一般認為它有兩個半規管，而盲鰻——也是圓口魚——只有一個，這在過去被認為是一種更原始的特徵。

然而，最近的分子和發育分析有力地支持了圓口魚的單一性，這使得脊椎動物內耳的進化軌跡尚不清楚。

這裡，研究人員展示了東亞叉牙七鰓鰻和近岸布氏黏盲鰻的耳泡分化。這些結果有助於了解圓口魚內耳發育和脊椎動物半規管進化。

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.

物理Physics

Quantum Hall effect based on Weyl orbits inCd₃As₂

砷化鎘中基於外爾軌道的量子霍爾效應

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

鏈接：

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

摘要：

對通電的導體加上垂直於電流方向的磁場，電子的運動軌跡將發生偏轉，在導體的縱向方向產生電壓,這個電磁現象就是「霍爾效應」。

但以往的實驗證明，量子霍爾效應只會在二維或准二維體系中發生。本研究基於三維拓撲半金屬材料Cd₃As₂，發現一種新型的量子霍爾效應，認為三維量子霍爾效應的來源於與外爾軌道。

研究人員利用楔形Cd₃As₂納米片，發現樣品厚度對量子霍爾輸運產生極大的調製。這一發現為未來三維空間電子的量子化傳輸提供了新的思路和實驗基礎。

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 Cd₃As₂nanostructures 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.

《自然》（20190117出版）一周論文導讀