《科學》（20190215出版）一周論文導讀

知識 02-16

翻譯 | 唐一塵

Science, 15 FEBRUARY 2019, VOL 363, ISSUE 6428

《科學》2019年2月15日，第6428期363卷

《科學》（20190215出版）一周論文導讀

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生物Biology

Parallel adaptation of rabbit populations to myxoma virus

兔群能抵抗粘液瘤病毒

作者：Joel M. Alves、MiguelCarneiro、Jade Y. Cheng，et al

鏈接：

http://science.sciencemag.org/content/early/2019/02/13/science.aau7285

摘要：

在1950年代，人們在歐洲和澳大利亞的兔群中釋放出了粘液瘤病毒（MYXV），試圖以此遏制兔群的快速增長和其造成的破壞。

該病毒的釋出大量殺死了該整個地區內的兔子，但它也刺激了兔群快速演化出了對該病毒的抵抗力。但人們對這一抵抗力的遺傳基礎仍然所知甚少。

本研究對來自澳大利亞、法國和英國的總共152個兔子的標本進行了測序，並將現代兔子的外顯子組與那些歷史性兔子標本的外顯子組進行了比較，結果顯示，所有這3個國家中的兔子都具有強力的平行演化模式，該演化會選擇有利於許多相同等位基因的基因變異。

此外，許多變化發生在與免疫力相關的基因中，而在每個兔群中的抵抗力平行演化如此相像且快速的原因可能是對存在於先祖兔群中的常備基因變異的自然選擇。

Abstract

In the 1950s the myxoma virus was released into European rabbit populations in Australia and Europe, decimating populations and resulting in the rapid evolution of resistance. We investigated the genetic basis of resistance by comparing the exomes of rabbits collected before and after the pandemic. We found a strong pattern of parallel evolution, with selection on standing genetic variation favoring the same alleles in Australia, France and the United Kingdom. Many of these changes occurred in immunity-related genes, supporting a polygenic basis of resistance. We experimentally validated the role of several genes in viral replication and showed that selection acting on an interfer on protein has increased its antiviral effect.

The human gut bacterial genotoxin colibactin alkylates DNA

人類腸道微生物基因毒素「打碎」DNA

作者：Matthew R. Wilson、Yindi Jiang、Peter W.Villalta，et al

鏈接：

http://science.sciencemag.org/content/363/6428/eaar7785

摘要：

大腸桿菌素被認為是含有生物合成基因簇（被稱作pks島）大腸桿菌株的一種產物。接觸該基因毒素已被證明會在哺乳動物細胞內通過令其DNA組成鏈變成碎片，誘導基因突變及腫瘤生長率增加而引發嚴重的基因損害。

但該基因毒素的化學性質、其促致癌作用及它如何進入被其摧毀的細胞等機制尚不清楚。

本研究使用了一種新近研發的基於非靶向質譜測定的方法（LC-MS3 DNA加成化合物組學）；當大腸桿菌素在人類活細胞中介導DNA損壞之後，研究人員發現了兩種殘剩的化學產物。新發現的大腸桿菌素加成化合物首次就通過某環丙烷的烷基化「彈頭」是該基因毒素摧毀DNA的潛在機制提供了直接證據。

此外，這些數據表明，這些加成化合物是接觸pks+大腸桿菌的生物標記，它們能為結腸直腸癌的預後提供信息。

Abstract

Certain Escherichia colistrains residing inthe human gut produce colibactin, a small-molecule genotoxin implicated in colorectal cancer pathogenesis. However, colibactin』s chemical structure andthe molecular mechanism underlying its genotoxic effects have remained unknown for more than a decade. Here we combine an untargeted DNA adductomics approach with chemical synthesis to identify and characterize a covalent DNA modification from human cell lines treated with colibactin-producingE. coli. Our dataestablish that colibactin alkylates DNA with an unusual electrophilic cyclopropane. We show that this metabolite is formed in mice colonized by colibactin-producing E.coli and is likely derived from an initially formed, unstable colibactin-DNA adduct. Our findings reveal a potential biomarker for colibactin exposure and provide mechanistic insights into how a gut microbe may contributeto colorectal carcinogenesis.

材料學/工程學

Materials Science/Engineering

Double-negative-index ceramic aerogels for thermal superinsulation

新陶瓷氣凝膠可控制最高溫度不造成傷害

作者：Xiang Xu、Qiangqiang Zhang、Menglong Hao、Yuan Hu、Zhaoyang Lin、Lele Peng、Tao Wang，et al

鏈接：

http://science.sciencemag.org/content/363/6428/723

摘要：

氣凝膠是一種主要由包含在某固態媒介網路（如陶瓷、金屬或碳）內的空氣組成的複合材料。陶瓷氣凝膠很輕，並擁有可在苛刻環境中發揮作用材料所需的理想特性。

然而，大多數常規性的陶瓷氣凝膠是脆性的，它們容易在長時間接觸高溫或溫度出現大幅和快速擺動時退化。

本研究用薄如原子的六邊形氮化硼片材所設計的一種獨特的陶瓷氣凝膠，並實現了負泊松比（這是某材料在被壓縮時向外膨脹傾向的檢測指標）及負熱膨脹係數。

研究人員將該氣凝膠反覆加熱至900 ℃並接著將其快速冷卻至-198 ℃，其變化速率達每秒275 ℃；還通過在真空中將其與接近1500 ℃的溫度接觸評估長期溫度應激的作用。

結果顯示，在經過嚴格的試驗之後，該氣凝膠基本保持不變，其強度喪失近乎為零。

Abstract

Ceramic aerogels are attractive for thermal insulation but plagued by poor mechanical stability and degradation under thermal shock. In this study, we designed and synthesized hyperbolic architectured ceramic aerogels with nanolayered double-pane walls with anegative Poisson』s ratio (?0.25) and a negative linear thermal expansion coefficient (?1.8 × 10^?6per °C). Our aerogels display robust mechanical and thermal stability and feature ultralow densities down to ~0.1 milligram percubic centimeter, superelasticity up to 95%, and near-zero strength loss aftersharp thermal shocks (275°C per second) or intense thermal stress at 1400°C, aswell as ultralow thermal conductivity in vacuum [~2.4 milliwatts permeter-kelvin (mW/m·K)] and in air (~20 mW/m·K). This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.

Printed subthreshold organic transistorsoperating at high gain and ultralow power

在高增益和超低功率下工作的有機晶體管

作者：Chen Jiang、HyungWoo Choi、Xiang Cheng、Hanbin Ma、DavidHasko、Arokia Nathan，et al

鏈接：

http://science.sciencemag.org/content/363/6428/719

摘要：

克服功耗、製造成本和信號放大之間的權衡一直是可穿戴電子產品面臨的一個長期問題。

本研究報告了一種高增益、全噴墨印刷肖特基勢壘有機薄膜晶體管放大器。晶體管信號放大效率為38.2西門子每安培，接近理論熱離子極限，而且有超低功耗（<1納瓦）。

肖特基勢壘的使用提供了晶體管幾何獨立的電氣特性，並適應了噴墨列印特性的大尺寸變化。

這些晶體管具有良好的可靠性，閾值電壓漂移可以忽略。

Abstract

Overcoming the trade-offs among power consumption, fabrication cost, and signal amplification has been along-standing issue for wearable electronics. We report a high-gain, fully inkjet-printed Schottky barrier organic thin-film transistor amplifier circuit. The transistor signal amplification efficiency is 38.2 siemens per ampere, which is near the the oretical thermionic limit, with an ultralow power consumption of <1 nanowatt. The use of a Schottky barrier for the source gave the transistor geometry-independent electrical characteristics and accommodated the large dimensional variation in inkjet-printed features. These transistors exhibited good reliability with negligible threshold-voltage shift. We demonstrated this capability with an ultralow-power high-gain amplifier for the detection of electro physiological signals and showed a signal-to-noiseratio of >60 decibels and noise voltage of <0.3 microvolt per hertz1/2 at100 hertz.

化學Chemistry

Inferring Earth』s discontinuous chemical layering from the 660-kilometer boundary topography

從660公里的邊界地形推斷出地球的不連續化學層

作者：Wenbo Wu、SidaoNi、Jessica C. E. Irving

鏈接：

http://science.sciencemag.org/content/363/6428/736

摘要：

固態地球中某些界面的地形或深度變化可以為人們了解地球內部的動力學提供重要見解。

雖然科學家已經很好地研究了地球上地幔和下地幔之間660公裡邊界的中、長期地形變化，但小規模的測量則更具挑戰性。

本研究利用分散的P"P"地震波，沿著660公里的邊界，發現了某些地區在短尺度上呈現出驚人數量的地形。

該觀測結果需要在短尺度粗糙度高的區域進行化學分層。相比之下，研究人員並沒有在上地幔410公里的邊界上看到如此小規模的地形。該發現支持了上地幔和下地幔之間部分阻塞或不完全環流的概念。

Abstract

Topography, or depth variation, ofcertain interfaces in the solid Earth can provide important insights into the dynamics of our planet interior. Although the intermediate- and long-range topographic variation of the 660-kilometer boundary between Earth』s upper andlower mantle is well studied, small-scale measurements are far more challenging. We found a surprising amount of topography at short length scalealong the 660-kilometer boundary in certain regions using scattered P"P" seismic waves. Our observations required chemical layering in regions with high short-scale roughness. By contrast, we did not see such small-scale topography along the 410-kilometer boundary in the upper mantle. Our ?ndings support the concept of partially blocked or imperfect circulation between the upper and lower mantle.

政策Policy

Long delays in banning trade in threatened species

禁止瀕危物種貿易的長期拖延

作者：Eyal G. Frank、David S. Wilcove

鏈接：

http://science.sciencemag.org/content/363/6428/686

摘要：

國際性的野生動植物貿易對全球數千個物種造成了威脅，它還加重了源自其他類型人類活動（如棲息地喪失與氣候變化）所致的生物多樣性的喪失。

為了緩解該問題，人們締結了《瀕危野生動植物種國際貿易公約》協議，旨在禁止對受到威脅物種進行交易。

研究人員用《國際自然保護聯盟》（IUCN）「紅色名錄」評估了物種在被確定為受到國際交易威脅之後得到公約保護會有多快。

結果顯示，國際性保護滯後於某一物種被確認有滅絕風險的時間。

研究人員表示，縮短科學評估與向這些受到困擾物種提供國際性保護之間的滯後對避免受到剝削利用的野生動植物的不必要的滅絕是至關重要的。

Abstract

The harvesting of wild animals and plants for international trade affects thousands of species, and compounds ongoing extinction threats such as habitat loss and climate change. The loss of overexploited species can result in cascading effects that reduce overall ecosystem functioning. The primary international framework for preventing the loss of species due to international wildlife trade is the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Given that CITES aims to be as scientifically based as possible, we analyzed how quickly species that are identified by the International Union for Conservation of Nature (IUCN) Red List as being threatened from trade are subsequently protected under CITES. The Red List represents an authoritative body of scientific knowledge regarding extinction risks. We find that in nearly two-thirds of the cases, the CITES process of regulating trade in threatened species lags considerably behind the IUCN identification of species in need ofprotection from trade. Such delay in the application of scientific knowledge topolicy formulation could result in species extinctions. With signatories to CITES set to gather in May to determine which species merit protection, we suggest opportunities to improve this process.

《科學》（20190215出版）一周論文導讀