原文地址：http://news.sciencenet.cn/htmlnews/2023/8/506858.shtm
編譯 | 李言
Science, 18 AUG 2023, Volume 381 Issue 6659
《科學》2022年8月18日，第381卷，6659期
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生物物理學Biophysics
Alcanivorax borkumensis biofilms enhance oil degradation by interfacial tubulation
泊庫島食烷菌生物膜通過界面管化促進石油降解
▲ 作者：M. PRASAD, N. OBANA et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.adf3345
▲ 摘要：
在消耗烷烴的過程中，泊庫島食烷菌會在油滴周圍形成生物膜，但這在降解過程中所起的作用尚不清楚。
我們發現了生物膜形態的變化取決于對石油消耗的適應：長時間的暴露導致樹突狀生物膜的出現，通過界面的管狀影響優化了石油消耗。原位微流體跟蹤使我們能夠將管狀與界面細胞有序中的局部缺陷聯系起來。
我們演示了通過使用限制來定位缺陷來控制液滴變形，從而使得液滴產生凹陷。我們開發了一個模型來解釋生物膜形態，將微管化與界面張力降低和細胞疏水性增加聯系起來。
▲ 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.
天體物理學Astrophysics
A massive helium star with a sufficiently strong magnetic field to form a magnetar
有足夠強磁場形成磁星的大質量氦恒星
▲ 作者：TOMER SHENAR, GREGG A. WADE, PABLO MARCHANT et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.ade3293
▲ 摘要：
磁星是高度磁化的中子星，但形成機制尚不清楚。光譜以發射線為主的富氦恒星，被稱為沃爾夫-拉葉星。
我們用光譜偏振法觀測了雙星系統HD 45166，并利用檔案數據重新分析了它的軌道。我們發現該星系中有一顆沃爾夫-拉葉星，其質量是太陽的2倍，磁場為43千高斯。
恒星演化計算表明，這顆星將爆炸成為一顆超新星，而它的磁場強大到足以讓超新星留下磁星遺跡。我們提出磁化的沃爾夫-拉葉星是由兩顆低質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.
光學Optics
Overcoming losses in superlenses with synthetic waves of complex frequency
用復頻率合成波克服超透鏡損耗
▲ 作者：FUXIN GUAN, XIANGDONG GUO, KEBO ZENG et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.adi1267
▲ 摘要：
展示出時間衰減行為的復頻率光波被提出通過引入虛擬增益來抵消超透鏡的本征損失，但是由于具有時間衰減的成像測量困難，一直很難在實驗中實現。
在這項研究中，我們提出了一種基于實際頻率測量的多頻方法來構建復頻率光波。這種方法允許我們在實驗上實現虛擬增益并觀察深亞波長圖像。我們的研究為克服成像和傳感應用中等離子體系統的固有損耗提供了一個實用的解決方案。
▲ 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.
物理學Physics
Ergodicity breaking in rapidly rotating C60 fullerenes
快速旋轉的C60富勒烯的遍歷性破壞
▲ 作者：LEE R. LIU, DINA ROSENBERG et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.adi6354
▲ 摘要：
在這里，我們報告了在一個前所未有的大分子12C60中觀察到的旋轉遍歷性破壞，這是從它的二十面體旋轉振動精細結構中確定的。
遍歷性斷裂發生在遠低于振動遍歷性閾值的地方，并且隨著角動量的增加，在遍歷和非遍歷狀態之間表現出多次轉變。
這些特殊的動力學來源于分子的對稱、大小和剛性的組合，突出了它與介觀量子系統中涌現現象的相關性。
▲ 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.
生物學Biology
Design of stimulus-responsive two-state hinge proteins
刺激反應雙態鉸鏈蛋白的設計
▲ 作者：FLORIAN PRAETORIUS, PHILIP J. Y. LEUNG et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.adg7731
▲ 摘要：
設計具有兩種不同但結構完整的蛋白質是蛋白質設計中的一大挑戰，因為它需要雕刻具有兩個不同最小值的能量景觀。
在此，我們描述了“鉸鏈”蛋白的設計，它在沒有配體的情況下可以形成一種設計狀態，在配體存在的情況下形成另一種設計狀態。X射線晶體學、電子顯微鏡、雙電子-電子共振光譜和結合測量表明，盡管存在顯著的結構差異，但這兩種狀態的設計具有原子水平的精度，并且構象平衡和結合平衡是緊密耦合的。
▲ 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.
古生物學Paleontology
Pre–Younger Dryas megafaunal extirpation at Rancho La Brea linked to fire-driven state shift
新仙女木時期之前，拉布雷亞牧場的巨型動物滅絕與火災驅動的狀態轉變有關
▲ 作者：F. ROBIN O’KEEFE, REGAN E. DUNN et al.
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.abo3594
▲ 摘要：
更新世巨型動物滅絕的原因很難確定，部分原因是化石記錄的較差時空分辨率阻礙了物種消失與考古和環境數據的對齊。我們在加州拉布雷亞牧場的大型動物遺跡中獲得172個新的放射性碳年代，時間距今1.56萬年至1萬年前。
有7種滅絕的巨型動物消失于1.29 萬年前，在新仙女木期開始前。與高分辨率區域數據集的比較表明，這些消失與暖期（1.469 ~ 1.289萬年）干旱化和植被變化引起的生態狀態轉變相吻合。
時間序列模型表明，大規模火災是物種滅絕的主要原因，而這種狀態轉變的催化劑可能是人類對干旱、變暖和越來越容易發生火災的生態系統的影響。
▲ Abstract：