氨基酸的衍生(《科学》（20190719出版）一周论文导读)

氨基酸的衍生

《科学学研究》

翻译 | 宗华

Science, 19 JULY 2019, VOL 365, ISSUE 6450

《科学》2019年7月19日，第6450期365卷

物理学Physics

Quantum scale anomaly and spatial coherence in a 2D Fermi superfluid

二维费米超流体的量子尺度异常与空间相干性

作者：Puneet A. Murthy, Nicolò Defenu, Luca Bayha , et al

链接：

https://science.sciencemag.org/content/365/6450/268

摘要：

量子异常是由于某些经典理论量化过程中出现分歧而违反了经典尺度对称性。虽然它们在多体系统的量子场理论描述中发挥着重要作用，但对实验观测结果的影响难以识别。

在这项研究中，我们发现了一种独特的量子异常表现形式。其出现在超冷原子的二维（2D）费米超流体的动量空间动力学中。超流体在呼吸模式周期中的对动量分布在强相互作用机制下表现出尺度破坏。

我们发现，该系统中以长程相位相关为特征的幂律尾指数被量子异常修正，从而强调了这种效应对2D超流体临界性质的影响。

Abstract

Quantum anomalies are violations of classical scaling symmetries caused by divergences that appear in the quantization of certain classical theories. Although they play a prominent role in the quantum field theoretical description of many-body systems, their influence on experimental observables is difficult to discern. In this study, we discovered a distinctive manifestation of a quantum anomaly in the momentum-space dynamics of a two-dimensional (2D) Fermi superfluid of ultracold atoms. The measured pair momentum distributions of the superfluid during a breathing mode cycle exhibit a scaling violation in the strongly interacting regime. We found that the power-law exponents that characterize long-range phase correlations in the system are modified by the quantum anomaly, emphasizing the influence of this effect on the critical properties of 2D superfluids.

Reconfigurable ferromagnetic liquid droplets

可重构铁磁液滴

作者：Xubo Liu, NoahKent, Alejandro Ceballos, et al

链接：

https://science.sciencemag.org/content/365/6450/264

摘要：

固体铁磁性材料的形状是刚性的，无法重构。铁磁流体虽然可重构，但在室温下是顺磁性的。同时，当外加磁场被移除时，铁磁流体的磁化强度会失去。

这里，我们展示了铁磁流体液滴由顺磁性向铁磁性的可逆转变。这是通过干扰组装在水—油界面的单层磁性纳米粒子实现的。这些铁磁性液滴表现出有限的矫顽力和剩余磁化强度。

它们可以很容易地重构成不同形状，同时保留具有经典南北偶极相互作用的固态铁磁体的磁性能。它们的平移和旋转运动可通过外部磁场进行远程和精确的驱动，从而为关于活性物质、耗能组件和可编程液体结构的研究提供了灵感。

Abstract

Solid ferromagnetic materials are rigid in shape and cannot be reconfigured. Ferrofluids, although reconfigurable, are paramagnetic at room temperature and lose their magnetization when the applied magnetic field is removed. Here, we show a reversible paramagnetic-to-ferromagnetic transformation of ferrofluid droplets by the jamming of a monolayer of magnetic nanoparticles assembled at the water-oil interface. These ferromagnetic liquid droplets exhibit a finite coercivity and remanent magnetization. They can be easily reconfigured into different shapes while preserving the magnetic properties of solid ferromagnets with classic north-south dipole interactions. Their translational and rotational motions can be actuated remotely and precisely by an external magnetic field, inspiring studies on active matter, energy-dissipative assemblies, and programmable liquid constructs.

生物学Biology

Amyloid β oligomers constrict human capillaries in Alzheimer’s disease via signaling to pericytes

β淀粉样蛋白寡聚物通过向周细胞发送信号使阿尔茨海默氏症的人体毛细血管收缩

作者：Ross Nortley, Nils Korte, Pablo Izquierdo, et al

链接：

https://science.sciencemag.org/content/365/6450/eaav9518

摘要：

在阿尔茨海默氏症（AD）刚发作时，脑血流量就会减少。由于脑内大部分血管阻力存在于毛细血管中，因此这可能反映了毛细血管壁令周细胞收缩的功能障碍。

我们利用活体和快速固定的人类组织建立了疾病相关性，并通过啮齿类动物实验确定了发病机制。

我们发现，在认知能力下降的人类中，淀粉样β（Aβ）使周细胞位置处的大脑毛细血管收缩。这是由Aβ生成活性氧引起的。活性氧诱发内皮素-1 （ET）的释放，而ET会激活外膜细胞ETA受体。

在AD小鼠模型中，毛细血管而非小动脉也发生了收缩。因此，抑制毛细血管收缩引起的Aβ可能减少AD的能量缺乏和神经退行性病变。

Abstract

Cerebral blood flow is reduced early in the onset of Alzheimer’s disease (AD). Because most of the vascular resistance within the brain is in capillaries, this could reflect dysfunction of contractile pericytes on capillary walls. We used live and rapidly fixed biopsied human tissue to establish disease relevance, and rodent experiments to define mechanism. We found that in humans with cognitive decline, amyloid β (Aβ) constricts brain capillaries at pericyte locations. This was caused by Aβ generating reactive oxygen species, which evoked the release of endothelin-1 (ET) that activated pericyte ETA receptors. Capillary, but not arteriole, constriction also occurred in vivo in a mouse model of AD. Thus, inhibiting the capillary constriction caused by Aβ could potentially reduce energy lack and neurodegeneration in AD.

Use of a scaffold peptide in the biosynthesis of amino acid–derived natural products

骨架肽在天然氨基酸衍物生物合成中的应用

作者：Chi P. Ting, Michael A. Funk, Steve L. Halaby, et al

链接：

https://science.sciencemag.org/content/365/6450/280

摘要：

环境细菌的基因组测序使识别生物合成基因簇成为可能。

环境细菌的基因组测序使识别生物合成基因簇成为可能。这种基因簇可编码产生未知天然产物的酶的不寻常组合。

我们确定了一种途径，其中一个核糖体合成小肽作为非核糖体肽延伸和化学修饰的支架。氨基酸通过三磷酸腺苷和独立于核糖体的依赖于氨基酰基tRNA的化学反应转移到肽的羧基端。

端半胱氨酸的氧化重排、羧甲基化和蛋白水解生成氨基酸衍生的小分子。微晶电子衍射结果表明，这些产物与谷氨酸是电子等排的。

我们发现，在具由细胞毒性的吡咯喹啉类生物碱ammosamide的生物合成过程中也使用了类似的肽延伸。这些结果为氨基酸衍生物的生物合成提供了一种新模式。

Abstract

Genome sequencing of environmental bacteria allows identification of biosynthetic gene clusters encoding unusual combinations of enzymes that produce unknown natural products. We identified a pathway in which a ribosomally synthesized small peptide serves as a scaffold for nonribosomal peptide extension and chemical modification. Amino acids are transferred to the carboxyl terminus of the peptide through adenosine triphosphate and amino acyl-tRNA–dependent chemistry that is independent of the ribosome. Oxidative rearrangement, carboxymethylation, and proteolysis of a terminal cysteine yields an amino acid–derived small molecule. Microcrystal electron diffraction demonstrates that the resulting product is isosteric to glutamate. We show that a similar peptide extension is used during the biosynthesis of the ammosamides, which are cytotoxic pyrroloquinoline alkaloids. These results suggest an alternative paradigm for biosynthesis of amino acid–derived natural products.

动物学Zoology

Conservation, acquisition, and functional impact of sex-biased gene expression in mammals

哺乳动物性别偏向基因表达的保持、获得和功能性影响

作者：Sahin Naqvi, Alexander K. Godfrey, Jennifer F. Hughes ,et al

链接：

https://science.sciencemag.org/content/365/6450/eaaw7317

摘要：

人类健康和疾病存在性别差异，那些被用作模型的其他哺乳动物也是如此。不过，性别差异在物种和组织间的分子水平上的保守程度目前尚不清楚。

我们调查了人类、猕猴、小鼠、大鼠和狗在12种组织中的基因表达上的性别差异。在每个组织中，我们发现了数百个具有保守的性别偏向表达的基因。这些发现结合人类身高的基因组分析，解释了女性和男性身高方面12%的差异。

我们推测，在基因表达上保守的性别偏向导致了特征上的性别差异。然而，大多数性别偏向的表达出现在哺乳动物的辐射过程中，这表明在建立人类性别差异的模型时需要仔细注意物种间的差异。

Abstract

Sex differences abound in human health and disease, as they do in other mammals used as models. The extent to which sex differences are conserved at the molecular level across species and tissues is unknown. We surveyed sex differences in gene expression in human, macaque, mouse, rat, and dog, across 12 tissues. In each tissue, we identified hundreds of genes with conserved sex-biased expression—findings that, combined with genomic analyses of human height, explain ~12% of the difference in height between females and males. We surmise that conserved sex biases in expression of genes otherwise operating equivalently in females and males contribute to sex differences in traits. However, most sex-biased expression arose during the mammalian radiation, which suggests that careful attention to interspecies divergence is needed when modeling human sex differences.

New Jurassic mammaliaform sheds light on early evolution of mammal-like hyoid bones

新的侏罗纪哺乳动物形态揭示了类哺乳动物舌骨的早期进化

作者：Chang-Fu Zhou, Bhart-Anjan S. Bhullar, April I. Neander, et al

链接：

https://science.sciencemag.org/content/365/6450/276

摘要：

我们报告了在中国发现的一种新的和舌骨一起保存下来的侏罗纪柱齿哺乳动物形态。它的基舌骨、角舌骨、上舌骨和舌骨大角均拥有活动关节，并呈鞍状排列，正如现存哺乳动物舌骨器官的活动连接一样。

它们和非哺乳动物形式的犬齿龙类简单的舌骨棒完全不同。后者可能与一个宽的、非肌化的喉咙存在关联，正如在现存爬行动物中看到的那样。舌骨器官为喉和狭窄的肌化食道提供了一个框架，对于现存哺乳动物咀嚼过的食物和液体的运输和强有力吞咽至关重要。

在哺乳动物冠群的中耳与下颌骨分离之前，舌骨的这些衍生结构组成便在早期分化的哺乳动物中进化出来。

Abstract

We report a new Jurassic docodontan mammaliaform found in China that is preserved with the hyoid bones. Its basihyal, ceratohyal, epihyal, and thyrohyal bones have mobile joints and are arranged in a saddle-shaped configuration, as in the mobile linkage of the hyoid apparatus of extant mammals. These are fundamentally different from the simple hyoid rods of nonmammaliaform cynodonts, which were likely associated with a wide, nonmuscularized throat, as seen in extant reptiles. The hyoid apparatus provides a framework for the larynx and for the constricted, muscularized esophagus, crucial for transport and powered swallowing of the masticated food and liquid in extant mammals. These derived structural components of hyoids evolved among early diverging mammaliaforms, before the disconnection of the middle ear from the mandible in crown mammals.

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《科学》（20190719出版）一周论文导读,《科学学研究》