编译 | 李言

Science, 18 AUG 2023, Volume 381 Issue 6659

《科学》2022年8月18日，第381卷，6659期

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生物物理学Biophysics

Alcanivorax borkumensis biofilms enhance oil degradation by interfacial tubulation

泊库岛食烷菌生物膜通过界面管化促进石油降解

▲ 作者：M. PRASAD, N. OBANA et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.adf3345

▲ 摘要：

在消耗烷烃的过程中，泊库岛食烷菌会在油滴周围形成生物膜，但这在降解过程中所起的作用尚不清楚。

我们发现了生物膜形态的变化取决于对石油消耗的适应：长时间的暴露导致树突状生物膜的出现，通过界面的管状影响优化了石油消耗。原位微流体跟踪使我们能够将管状与界面细胞有序中的局部缺陷联系起来。

我们演示了通过使用限制来定位缺陷来控制液滴变形，从而使得液滴产生凹陷。我们开发了一个模型来解释生物膜形态，将微管化与界面张力降低和细胞疏水性增加联系起来。

▲ Abstract：

During the consumption of alkanes, Alcanivorax borkumensis will form a biofilm around an oil droplet, but the role this plays during degradation remains unclear. We identified a shift in biofilm morphology that depends on adaptation to oil consumption: Longer exposure leads to the appearance of dendritic biofilms optimized for oil consumption effected through tubulation of the interface. In situ microfluidic tracking enabled us to correlate tubulation to localized defects in the interfacial cell ordering. We demonstrate control over droplet deformation by using confinement to position defects, inducing dimpling in the droplets. We developed a model that elucidates biofilm morphology, linking tubulation to decreased interfacial tension and increased cell hydrophobicity.

天体物理学Astrophysics

A massive helium star with a sufficiently strong magnetic field to form a magnetar

有足够强磁场形成磁星的大质量氦恒星

▲ 作者：TOMER SHENAR, GREGG A. WADE, PABLO MARCHANT et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.ade3293

▲ 摘要：

磁星是高度磁化的中子星，但形成机制尚不清楚。光谱以发射线为主的富氦恒星，被称为沃尔夫-拉叶星。

我们用光谱偏振法观测了双星系统HD 45166，并利用档案数据重新分析了它的轨道。我们发现该星系中有一颗沃尔夫-拉叶星，其质量是太阳的2倍，磁场为43千高斯。

恒星演化计算表明，这颗星将爆炸成为一颗超新星，而它的磁场强大到足以让超新星留下磁星遗迹。我们提出磁化的沃尔夫-拉叶星是由两颗低质量氦恒星合并形成的。

▲ Abstract：

Magnetars are highly magnetized neutron stars, the formation mechanism of which is unknown. Hot helium-rich stars with spectra dominated by emission lines are known as Wolf-Rayet stars. We observed the binary system HD 45166 using spectropolarimetry and reanalyzed its orbit using archival data. We found that the system contains a Wolf-Rayet star with a mass of 2 solar masses and a magnetic field of 43 kilogauss. Stellar evolution calculations indicate that this component will explode as a supernova, and that its magnetic field is strong enough for the supernova to leave a magnetar remnant. We propose that the magnetized Wolf-Rayet star formed by the merger of two lower-mass helium stars.

光学Optics

Overcoming losses in superlenses with synthetic waves of complex frequency

用复频率合成波克服超透镜损耗

▲ 作者：FUXIN GUAN, XIANGDONG GUO, KEBO ZENG et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.adi1267

▲ 摘要：

展示出时间衰减行为的复频率光波被提出通过引入虚拟增益来抵消超透镜的本征损失，但是由于具有时间衰减的成像测量困难，一直很难在实验中实现。

在这项研究中，我们提出了一种基于实际频率测量的多频方法来构建复频率光波。这种方法允许我们在实验上实现虚拟增益并观察深亚波长图像。我们的研究为克服成像和传感应用中等离子体系统的固有损耗提供了一个实用的解决方案。

▲ Abstract：

Optical waves of complex frequency that exhibit a temporally attenuating behavior have been proposed to offset the intrinsic losses in superlenses through the introduction of virtual gain, but experimental realization has been lacking because of the difficulty of imaging measurements with temporal decay. In this work, we present a multifrequency approach to constructing synthetic excitation waves of complex frequency based on measurements at real frequencies. This approach allows us to implement virtual gain experimentally and observe deep-subwavelength images. Our work offers a practical solution to overcome the intrinsic losses of plasmonic systems for imaging and sensing applications.

物理学Physics

Ergodicity breaking in rapidly rotating C60 fullerenes

快速旋转的C60富勒烯的遍历性破坏

▲ 作者：LEE R. LIU, DINA ROSENBERG et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.adi6354

▲ 摘要：

在这里，我们报告了在一个前所未有的大分子12C60中观察到的旋转遍历性破坏，这是从它的二十面体旋转振动精细结构中确定的。

遍历性断裂发生在远低于振动遍历性阈值的地方，并且随着角动量的增加，在遍历和非遍历状态之间表现出多次转变。

这些特殊的动力学来源于分子的对称、大小和刚性的组合，突出了它与介观量子系统中涌现现象的相关性。

▲ Abstract：

Here, we report the observation of rotational ergodicity breaking in an unprecedentedly large molecule, 12C60, determined from its icosahedral rovibrational fine structure. The ergodicity breaking occurs well below the vibrational ergodicity threshold and exhibits multiple transitions between ergodic and nonergodic regimes with increasing angular momentum. These peculiar dynamics result from the molecule’s distinctive combination of symmetry, size, and rigidity, highlighting its relevance to emergent phenomena in mesoscopic quantum systems.

生物学Biology

Design of stimulus-responsive two-state hinge proteins

刺激反应双态铰链蛋白的设计

▲ 作者：FLORIAN PRAETORIUS, PHILIP J. Y. LEUNG et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.adg7731

▲ 摘要：

设计具有两种不同但结构完整的蛋白质是蛋白质设计中的一大挑战，因为它需要雕刻具有两个不同最小值的能量景观。

在此，我们描述了“铰链”蛋白的设计，它在没有配体的情况下可以形成一种设计状态，在配体存在的情况下形成另一种设计状态。X射线晶体学、电子显微镜、双电子-电子共振光谱和结合测量表明，尽管存在显著的结构差异，但这两种状态的设计具有原子水平的精度，并且构象平衡和结合平衡是紧密耦合的。

▲ Abstract：

Designing proteins with two distinct but fully structured conformations is a challenge for protein design as it requires sculpting an energy landscape with two distinct minima. Here we describe the design of “hinge” proteins that populate one designed state in the absence of ligand and a second designed state in the presence of ligand. X-ray crystallography, electron microscopy, double electron-electron resonance spectroscopy, and binding measurements demonstrate that despite the significant structural differences the two states are designed with atomic level accuracy and that the conformational and binding equilibria are closely coupled.

古生物学Paleontology

Pre–Younger Dryas megafaunal extirpation at Rancho La Brea linked to fire-driven state shift

新仙女木时期之前，拉布雷亚牧场的巨型动物灭绝与火灾驱动的状态转变有关

▲ 作者：F. ROBIN O’KEEFE, REGAN E. DUNN et al.

▲ 链接：https://www.science.org/doi/full/10.1126/science.abo3594

▲ 摘要：

更新世巨型动物灭绝的原因很难确定，部分原因是化石记录的较差时空分辨率阻碍了物种消失与考古和环境数据的对齐。我们在加州拉布雷亚牧场的大型动物遗迹中获得172个新的放射性碳年代，时间距今1.56万年至1万年前。

有7种灭绝的巨型动物消失于1.29 万年前，在新仙女木期开始前。与高分辨率区域数据集的比较表明，这些消失与暖期（1.469 ~ 1.289万年）干旱化和植被变化引起的生态状态转变相吻合。

时间序列模型表明，大规模火灾是物种灭绝的主要原因，而这种状态转变的催化剂可能是人类对干旱、变暖和越来越容易发生火灾的生态系统的影响。

▲ Abstract：

The cause, or causes, of the Pleistocene megafaunal extinctions have been difficult to establish, in part because poor spatiotemporal resolution in the fossil record hinders alignment of species disappearances with archeological and environmental data. We obtained 172 new radiocarbon dates on megafauna from Rancho La Brea in California spanning 15.6 to 10.0 thousand calendar years before present (ka). Seven species of extinct megafauna disappeared by 12.9 ka, before the onset of the Younger Dryas. Comparison with high-resolution regional datasets revealed that these disappearances coincided with an ecological state shift that followed aridification and vegetation changes during the B?lling-Aller?d (14.69 to 12.89 ka). Time-series modeling implicates large-scale fires as the primary cause of the extirpations, and the catalyst of this state shift may have been mounting human impacts in a drying, warming, and increasingly fire-prone ecosystem.