《科學》（20240719出版）一周論文導讀

Science, 19 July 2024, Volume 385，Issue 6706

《科學》2024年7月19日，第385卷，6706期

化學Chemistry

Synthesis of a stable crystalline nitrene

一種穩定結晶亞硝烯的合成

▲ 作者：MARVIN JANSSEN, THOMAS FREDERICHS, MARIAN OLARU, ENNO LORK, EMANUEL HUPF, AND JENS BECKMANN

▲鏈接：

https://www.science.org/doi/10.1126/science.adp4963

▲摘要：

氮在其化合物中通常形成三個鍵。在某些情況下，它可以存在于只有一個鍵的基序中，但這些亞硝基分子往往具有極短的壽命，并且通過時間分辨光譜可以短暫地觀察到。

最近，一類笨重的芳基框架穩定了氮的重同系物，銻和鉍的亞硝基類似物。研究者發現，這樣的框架也可以穩定亞硝基。該化合物被分離并進行了晶體學表征，電子順磁共振波譜支持三重態基態。

▲ 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: 穩定的碳原子轉移試劑

▲ 作者：TAICHI KOIKE, JHEN-KUEI YU, AND MAX M. HANSMANN

▲鏈接：

https://www.science.org/doi/10.1126/science.ado4564

▲摘要：

在單原子水平上對分子中的化學位點進行精確修飾是化學中最優雅但又最困難的轉化之一。為單原子碳的化學選擇性引入而專門設計的試劑是一項特別艱巨的挑戰。

研究者報告了一個直接的、無疊氮化物的結晶和可分離的化合物Ph₃PCN₂，這是一種穩定的化合物，其碳原子會連接到兩個不穩定的化學基團，PPh₃和N₂。在不添加任何添加劑的情況下，重氮磷酰化作為包括Ph₃PCN在內的片段的高選擇性轉移試劑，傳遞端磷酰化的雜環烯和CN₂，生成多取代吡唑。

在與醛、無環酮和環酮（R₂C=0）的反應中，碳原子取代形成偏乙烯（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 diazophosphorus 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 TiO_x overlayers catalyze propane dehydrogenation promoted by base metals

由非貴金屬促進的有缺陷的TiO_x覆蓋層催化丙烷脫氫

▲ 作者：SAI CHEN, YIYI XU, XIN CHANG, YUE PAN, GUODONG SUN, XIANHUI WANG, DONGLONG FU, CHUNLEI PEI, ZHI-JIAN ZHAO, AND JINLONG GONG

▲鏈接：

https://www.science.org/doi/10.1126/science.adp7379

▲摘要：

丙烷脫氫（PDH）制丙烯的工業催化劑是石油基裂化工藝的重要替代品，要么使用昂貴的金屬，要么使用對環境不利的金屬氧化物。鈦納米片通常是相對較差的丙烷脫氫催化劑，當它們完全包裹金屬鎳時變得非常活躍。

研究者報道了一種典型的活性較低的氧化物，氧化鈦（TiO₂），可以與地球上豐富的金屬鎳（Ni）結合，形成一種非常規的Ni@TiO_x催化劑，用于高效的PDH。他們將鎳離子裝載到氧化鋁支撐的氧化鈦納米片上，然后在600°C的氫氣氣氛中還原它們。

該工藝完全封裝了金屬鎳，該催化劑在40%丙烷轉化率下具有94%的丙烯選擇性。氧空位周圍的四配位鈦是催化活性位點，地下金屬鎳是碳氫鍵活化的促進劑，促進了氫的脫附。

▲ 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.

物理學Physics

Dynamics of high-speed electrical tree growth in electron-irradiated polymethyl methacrylate

電子輻照聚甲基丙烯酸甲酯中高速電樹生長動力學

▲ 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

▲鏈接：

https://www.science.org/doi/10.1126/science.ado5943

▲摘要：

介電材料是現代通信、國防和商業需求的基礎。介質擊穿是這些系統失效的主要原因，但這一過程并不是分清楚。研究者分析了兩種不同類型的電樹的介電擊穿通道傳播動力學。其中一種電樹還沒有被正式分類。

他們觀察到這種電樹的傳播速度超過每秒1000萬米。這些結果確定了對介電擊穿理解的實質性空白，填補這些空白對于設計和工程中不易受靜電放電故障影響的介電材料至關重要。

▲ 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.

生物物理學Biophysics

Sculpting conducting nanopore size and shape through de novo protein design

通過從頭開始的蛋白質設計雕刻導電納米孔的大小和形狀

▲ 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

▲鏈接：

https://www.science.org/doi/10.1126/science.adn3796

▲摘要：

跨膜β—桶具有廣泛的傳感應用潛力。目前納米孔傳感器的工程方法僅限于自然發生的通道，這提供了次優的起點。相比之下，從頭開始的蛋白質設計原則上可以創造無限數量的新納米孔，具有任何所需的特性。

研究者描述了一種設計具有不同直徑和孔隙幾何形狀的跨膜β—桶孔的一般方法。核磁共振和晶體學表征表明，這些設計是穩定折疊的，結構與設計模型相似。這些設計具有不同的電導，與它們的孔徑相關，范圍從110皮西門子（~0.5納米孔徑）到430皮西門子（~1.1納米孔徑）。該方法為傳感和測序應用的跨膜納米孔定制設計打開了大門。

▲ 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.

生物化學Biochemistry

Multiscale photocatalytic proximity labeling reveals cell surface neighbors on and between cells

多尺度光催化接近標記揭示細胞表面和細胞之間的鄰居

▲ 作者：ZHI LIN, KAITLIN SCHAEFER, IRENE LUI, ZI YAO, ANDREA FOSSATI, DANIELLE L. SWANEY, AJIKARUNIA PALAR, ANDREJ SALI, AND JAMES A. WELLS

▲鏈接：

https://www.science.org/doi/10.1126/science.adl5763

▲摘要：

細胞表面蛋白質可以與同一細胞上的其他蛋白質或與其他細胞中的蛋白質在空間和時間上發生相互作用。相關研究進展已經提高了這些相互作用的分辨率，可以通過接近標記來識別，但是整合來自不同長度尺度的信息是一個挑戰。

研究者開發了一種使用有機光催化劑的方法，該方法可以激活幾種具有不同自由基半衰期的常見反應探針，這些探針對應于不同的距離尺度。他們使用一種稱為MultiMap的工作流程，確定了一種關鍵細胞表面受體的大量伴侶蛋白，并在T細胞免疫突觸模型中描述了細胞—細胞相互作用。

▲ 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.