《科学》（20190215出版）一周论文导读

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《科学》（20190215出版）一周论文导读

2019 年 2 月 15 日 科学网

翻译 | 唐一尘

Science, 15 FEBRUARY 2019, VOL 363, ISSUE 6428

《科学》2019年2月15日，第6428期363卷

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

▲ 链接：

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

▲ 摘要：

在1950年代，人们在欧洲和澳大利亚的兔群中释放出了粘液瘤病毒（MYXV），试图以此遏制兔群的快速增长和其造成的破坏。

该病毒的释出大量杀死了该整个地区内的兔子，但它也刺激了兔群快速演化出了对该病毒的抵抗力。但人们对这一抵抗力的遗传基础仍然所知甚少。

本研究对来自澳大利亚、法国和英国的总共152个兔子的标本进行了测序，并将现代兔子的外显子组与那些历史性兔子标本的外显子组进行了比较，结果显示，所有这3个国家中的兔子都具有强力的平行演化模式，该演化会选择有利于许多相同等位基因的基因变异。

此外，许多变化发生在与免疫力相关的基因中，而在每个兔群中的抵抗力平行演化如此相像且快速的原因可能是对存在于先祖兔群中的常备基因变异的自然选择。

▲ 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

人类肠道微生物基因毒素“打碎”DNA

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

▲ 链接：

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

▲ 摘要：

大肠杆菌素被认为是含有生物合成基因簇（被称作pks岛）大肠杆菌株的一种产物。接触该基因毒素已被证明会在哺乳动物细胞内通过令其DNA组成链变成碎片，诱导基因突变及肿瘤生长率增加而引发严重的基因损害。

但该基因毒素的化学性质、其促致癌作用及它如何进入被其摧毁的细胞等机制尚不清楚。

本研究使用了一种新近研发的基于非靶向质谱测定的方法（LC-MS3 DNA加成化合物组学）；当大肠杆菌素在人类活细胞中介导DNA损坏之后，研究人员发现了两种残剩的化学产物。新发现的大肠杆菌素加成化合物首次就通过某环丙烷的烷基化“弹头”是该基因毒素摧毁DNA的潜在机制提供了直接证据。

此外，这些数据表明，这些加成化合物是接触pks+大肠杆菌的生物标记，它们能为结肠直肠癌的预后提供信息。

▲ Abstract

Certain Escherichia coli strains 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-producing E. 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.

材料学/工程学

Materials Science/Engineering

Double-negative-index ceramic aerogels for thermal superinsulation

新陶瓷气凝胶可控制最高温度不造成伤害

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

▲ 链接：

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

▲ 摘要：

气凝胶是一种主要由包含在某固态媒介网络（如陶瓷、金属或碳）内的空气组成的复合材料。陶瓷气凝胶很轻，并拥有可在苛刻环境中发挥作用材料所需的理想特性。

然而，大多数常规性的陶瓷气凝胶是脆性的，它们容易在长时间接触高温或温度出现大幅和快速摆动时退化。

本研究用薄如原子的六边形氮化硼片材所设计的一种独特的陶瓷气凝胶，并实现了负泊松比（这是某材料在被压缩时向外膨胀倾向的检测指标）及负热膨胀系数。

研究人员将该气凝胶反复加热至900 ℃并接着将其快速冷却至-198 ℃，其变化速率达每秒275 ℃；还通过在真空中将其与接近1500 ℃的温度接触评估长期温度应激的作用。

结果显示，在经过严格的试验之后，该气凝胶基本保持不变，其强度丧失近乎为零。

▲ 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 × 10⁻⁶ per °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机晶体管

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

▲ 链接：

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

▲ 摘要：

克服功耗、制造成本和信号放大之间的权衡一直是可穿戴电子产品面临的一个长期问题。

本研究报告了一种高增益、全喷墨印刷肖特基势垒有机薄膜晶体管放大器。晶体管信号放大效率为38.2西门子每安培，接近理论热离子极限，而且有超低功耗（<1纳瓦）。

肖特基势垒的使用提供了晶体管几何独立的电气特性，并适应了喷墨打印特性的大尺寸变化。

这些晶体管具有良好的可靠性，阈值电压漂移可以忽略。

▲ 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.

化学Chemistry

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

从660公里的边界地形推断出地球的不连续化学层

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

▲ 链接：

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

▲ 摘要：

固态地球中某些界面的地形或深度变化可以为人们了解地球内部的动力学提供重要见解。

虽然科学家已经很好地研究了地球上地幔和下地幔之间660公里边界的中、长期地形变化，但小规模的测量则更具挑战性。

本研究利用分散的P'P'地震波，沿着660公里的边界，发现了某些地区在短尺度上呈现出惊人数量的地形。

该观测结果需要在短尺度粗糙度高的区域进行化学分层。相比之下，研究人员并没有在上地幔410公里的边界上看到如此小规模的地形。该发现支持了上地幔和下地幔之间部分阻塞或不完全环流的概念。

▲ 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 ﬁndings 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

禁止濒危物种贸易的长期拖延

▲ 作者：Eyal G. Frank、David S. Wilcove

▲ 链接：

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

▲ 摘要：

国际性的野生动植物贸易对全球数千个物种造成了威胁，它还加重了源自其他类型人类活动（如栖息地丧失与气候变化）所致的生物多样性的丧失。

为了缓解该问题，人们缔结了《濒危野生动植物种国际贸易公约》协议，旨在禁止对受到威胁物种进行交易。

研究人员用《国际自然保护联盟》（IUCN）“红色名录”评估了物种在被确定为受到国际交易威胁之后得到公约保护会有多快。

结果显示，国际性保护滞后于某一物种被确认有灭绝风险的时间。

研究人员表示，缩短科学评估与向这些受到困扰物种提供国际性保护之间的滞后对避免受到剥削利用的野生动植物的不必要的灭绝是至关重要的。

▲ 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.