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发布日期：2024-09-07 作者：开云
Science, 19 July 2024, Volume 385，Issue 6706
《科学》2024年7月19日，第385卷，6706期
一种不变结晶亚硝烯的合成
▲ 作者：MARVIN JANSSEN, THOMAS FREDERICHS, MARIAN OLARU, ENNO LORK, EMANUEL HUPF, AND JENS BECKMANN
▲链接：
https://www.science.org/doi/10.1126/science.adp4963
▲摘要：
氮在其化合物中凡是构成三个键。在某些环境下，它可以存在在只有一个键的基序中，但这些亚硝基份子常常具有极短的寿命，而且经由过程时候分辩光谱可以短暂地不雅察到。
比来，一类粗笨的芳基框架不变了氮的重同系物，锑和铋的亚硝基近似物。研究者发现，如许的框架也能够不变亚硝基。该化合物被分手并进行了晶体学表征，电子顺磁共振波谱撑持三重态基态。
▲ Abstract：
Nitrogen most commonly forms three bonds in its chemical compounds. In certain cases, it can persist in motifs with just one bond, but these nitrene molecules tend to have extremely short lifetimes and are seen transiently by time-resolved spectroscopy. Recently, a class of bulky aryl frameworks has stabilized nitrene analogs of nitrogen’s heavier congeners, antimony and bismuth. Janssen et al. now report that such a framework can stabilize a nitrene as well. The compound was isolated and characterized crystallographically, and electron paramagnetic resonance spectroscopy supported a triplet ground state.
Ph3PCN2: A stable reagent for carbon-atom transfer
Ph3PCN2: 不变的碳原子转移试剂
▲ 作者：TAICHI KOIKE, JHEN-KUEI YU, AND MAX M. HANSMANN
▲链接：
https://www.science.org/doi/10.1126/science.ado4564
▲摘要：
在单原子程度上对份子中的化学位点进行切确润色是化学中最优雅但又最坚苦的转化之一。为单原子碳的化学选择性引入而专门设计的试剂是一项特殊艰难的挑战。
研究者陈述了一个直接的、无叠氮化物的结晶和可分手的化合物Ph3PCN2，这是一种不变的化合物，其碳原子会毗连到两个不不变的化学基团，PPh3和N2。在不添加任何添加剂的环境下，重氮磷酰化作为包罗Ph3PCN在内的片断的高选择性转移试剂，传递端磷酰化的杂环烯和CN2，生成多代替吡唑。
在与醛、无环酮和环酮（R2C=0）的反映中，碳原子代替构成偏乙烯（R2C=C），然后生成炔或丁腈。
▲ Abstract：
Precise modification of a chemical site in a molecule at the single-atom level is one of the most elegant yet difficult transformations in chemistry. A reagent specifically designed for chemoselective introduction of monoatomic carbon is a particularly formidable challenge. Here, we report a straightforward, azide-free synthesis of a crystalline and isolable diazophos开云体育appphorus ylide, Ph3PCN2, a stable compound with a carbon atom bonded to two chemically labile groups, triphenylphosphine (PPh3) and dinitrogen (N2). Without any additives, the diazophosphorus ylide serves as a highly selective transfer reagent for fragments, including Ph3PCN, to deliver phosphorus ylide–terminated heterocumulenes and CN2 to produce multisubstituted pyrazoles. Ultimately, even exclusive carbon-atom transfer is possible. In reactions with aldehydes and acyclic and cyclic ketones (R2C=O), the carbon-atom substitution forms a vinylidene (R2C=C:) en route to alkynes or butatrienes.
Defective TiOx overlayers catalyze propane dehydrogenation promoted by base metals
由非贵金属增进的出缺陷的TiOx笼盖层催化丙烷脱氢
▲ 作者：SAI CHEN, YIYI XU, XIN CHANG, YUE PAN, GUODONG SUN, XIANHUI WANG, DONGLONG FU, CHUNLEI PEI, ZHI-JIAN ZHAO, AND JINLONG GONG
▲链接：
https://www.science.org/doi/10.1126/science.adp7379
▲摘要：
丙烷脱氢（PDH）制丙烯的工业催化剂是石油基裂化工艺的主要替换品，要末利用昂贵的金属，要末利用对情况晦气的金属氧化物。钛纳米片凡是是相对较差的丙烷脱氢催化剂，当它们完全包裹金属镍时变得很是活跃。
研究者报导了一种典型的活性较低的氧化物，氧化钛（TiO2），可以与地球上丰硕的金属镍（Ni）连系，构成一种很是规的Ni@TiOx催化剂，用在高效的PDH。他们将镍离子装载到氧化铝支持的氧化钛纳米片上，然后在600°C的氢气氛围中还原它们。
该工艺完全封装了金属镍，该催化剂在40%丙烷转化率下具有94%的丙烯选择性。氧空位四周的四配位钛是催化活性位点，地下金属镍是碳氢键活化的增进剂，增进了氢的脱附。
▲ Abstract：
Titanium nanosheets, which are normally relatively poor catalysts for propane dehydrogenation, become highly active when they completely encapsulate metallic nickel. Chen et al. loaded nickel ions onto titanium oxide nanosheets supported on alumina and then reduced them in a hydrogen atmosphere at 600°C. This process completely encapsulated the metallic nickel, and this catalyst displayed 94% propylene selectivity at 40% propane conversion. Tetra-coordinated titanium sites surrounding oxygen vacancies appeared to be the catalytically active site, and subsurface metallic nickel acted as a promoter for carbon-hydrogen bond activation and promoted hydrogen desorption.
物理学Physics
Dynamics of high-speed electrical tree growth in electron-irradiated polymethyl methacrylate
电子辐照聚甲基丙烯酸甲酯中高速电树发展动力学
▲ 作者：KATHRYN M. STURGE, NOAH HOPPIS, ARIANA M. BUSSIO, JONATHAN BARNEY, BRIAN BEAUDOIN, CAMERON BROWN, BRUCE CARLSTEN, CAROLYN CHUN, BRYSON C. CLIFFORD, AND TIMOTHY W. KOETH
▲链接：
https://www.science.org/doi/10.1126/science.ado5943
▲摘要：
介电材料是现代通讯、国防和贸易需求的根本。介质击穿是这些系统掉效的首要缘由，但这一进程其实不是分清晰。研究者阐发了两种分歧类型的电树的介电击穿通道传布动力学。此中一种电树还没有被正式分类。
他们不雅察到这类电树的传布速度跨越每秒1000万米。这些成果肯定了对介电击穿理解的本色性空白，弥补这些空白对设计和工程中不容易受静电放电故障影响的介电材料相当主要。
▲ Abstract：
Dielectric materials are foundational to our modern-day communications, defense, and commerce needs. Although dielectric breakdown is a primary cause of failure of these systems, we do not fully understand this process. We analyzed the dielectric breakdown channel propagation dynamics of two distinct types of electrical trees. One type of these electrical trees has not been formally classified. We observed the propagation speed of this electrical tree type to exceed 10 million meters per second. These results identify substantial gaps in the understanding of dielectric breakdown, and filling these gaps is paramount to the design and engineering of dielectric materials that are less susceptible to electrostatic discharge failure.
生物物理学Biophysics
Sculpting conducting nanopore size and shape through de novo protein design
经由过程从头最先的卵白质设计雕镂导电纳米孔的巨细和外形
▲ 作者：SAMUEL BERHANU, SAGARDIP MAJUMDER, THOMAS MüNTENER, JAMES WHITEHOUSE, CAROLIN BERNER, ASIM K. BERA, ALEX KANG, BINYONG LIANG, NASIR KHAN, AND ANASTASSIA A. VOROBIEVA
▲链接：
https://www.science.org/doi/10.1126/science.adn3796
▲摘要：
跨膜β—桶具有普遍的传感利用潜力。今朝纳米孔传感器的工程方式仅限在天然产生的通道，这供给了次优的出发点。比拟之下，从头最先的卵白质设计原则上可以缔造无穷数目的新纳米孔，具有任何所需的特征。
研究者描写了一种设计具有分歧直径和孔隙几何外形的跨膜β—桶孔的一般方式。核磁共振和晶体学表征注解，这些设计是不变折叠的，布局与设计模子类似。这些设计具有分歧的电导，与它们的孔径相干，规模从110皮西门子（~0.5纳米孔径）到430皮西门子（~1.1纳米孔径）。该方式为传感和测序利用的跨膜纳米孔定制设计打开了年夜门。
▲ Abstract：
Transmembrane β-barrels have considerable potential for a broad range of sensing applications. Current engineering approaches for nanopore sensors are limited to naturally occurring channels, which provide suboptimal starting points. By contrast, de novo protein design can in principle create an unlimited number of new nanopores with any desired properties. Here we describe a general approach to designing transmembrane β-barrel pores with different diameters and pore geometries. Nuclear magnetic resonance and crystallographic characterization show that the designs are stably folded with structures resembling those of the design models. The designs have distinct conductances that correlate with their pore diameter, ranging from 110 picosiemens (~0.5 nanometer pore diameter) to 430 picosiemens (~1.1 nanometer pore diameter). Our approach opens the door to the custom design of transmembrane nanopores for sensing and sequencing applications.
生物化学Biochemistry
Multiscale photocatalytic proximity labeling reveals cell surface neighbors on and between cells
多标准光催化接近标识表记标帜揭露细胞概况和细胞之间的邻人
▲ 作者：ZHI LIN, KAITLIN SCHAEFER, IRENE LUI, ZI YAO, ANDREA FOSSATI, DANIELLE L. SWANEY, AJIKARUNIA PALAR, ANDREJ SALI, AND JAMES A. WELLS
▲链接：
https://www.science.org/doi/10.1126/science.adl5763
▲摘要：
细胞概况卵白质可以与统一细胞上的其他卵白质或与其他细胞中的卵白质在空间和时候上产生彼此感化。相干研究进展已提高了这些彼此感化的分辩率，可以经由过程接近标识表记标帜来辨认，可是整合来自分歧长度标准的信息是一个挑战。
研究者开辟了一种利用有机光催化剂的方式，该方式可以激活几种具有分歧自由基半衰期的常见反映探针，这些探针对应在分歧的距离标准。他们利用一种称为MultiMap的工作流程，肯定了一种要害细胞概况受体的年夜量伴侣卵白，并在T细胞免疫突触模子中描写了细胞—细胞彼此感化。
▲ Abstract：
Cell surface proteins can have interactions with other proteins on the same cell or with proteins in other cells that vary in space and time. Recent advances have improved the resolution with which these interactions can be identified through proximity labeling, but it is a challenge to integrate information from different length scales. Lin et al. developed an approach that uses an organic photocatalyst that can activate several common reactive probes with different radical half-lives corresponding to different distance scales. Using a workflow called MultiMap, the authors identified a large number of partner proteins for a key cell surface receptor and profile cell-cell interactions in a T cell immune synapse model.
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