编译|冯维维

Science, 4 DEC 2025,VOLUME 390, ISSUE 6777 

《科学》2025年12月4日，第390卷，6777期

物理学Physics

Hexatic phase in covalent two-dimensional silver iodide

二维共价碘化银中的六角相

▲ 作者：THUY AN BUI, DAVID LAMPRECHT, JACOB MADSEN, MARCIN KURPAS, PETER KOTRUSZ, ALEXANDER MARKEVICH, CLEMENS MANGLER, JANI KOTAKOSKI, LADO FILIPOVIC , AND KIMMO MUSTONEN

▲链接：

https://www.science.org/doi/10.1126/science.adv7915

▲摘要：

根据KTHNY理论，二维体系中从固体到液体的转变会经过一个具有取向有序的类液六角相。然而，在一些二维系统中也观察到了其他混合熔化机制，即熔化过程同时涉及连续和非连续转变的六角相。

研究通过时间和温度分辨的原位原子分辨率扫描透射电子显微镜及纳米束电子衍射，对嵌入多层石墨烯中的碘化银进行了成像观察，并确认了六角相的存在，提供了支持混合熔化机制的证据。

▲ Abstract：

According to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory, the transition from a solid to liquid in two dimensions proceeds through an orientationally ordered liquid-like hexatic phase. However, alternative mixed melting scenarios, in which melting proceeds through the hexatic phase with both continuous and discontinuous transitions, have also been observed in some two-dimensional systems. In this study, we imaged silver iodide embedded in multilayer graphene using time- and temperature-resolved in situ atomic-resolution scanning transmission electron microscopy and nanobeam electron diffraction. We observed the hexatic phase and provide evidence supporting a mixed melting scenario.

Constraints on lepton number violation with the 2 tonne · year CUORE dataset

对轻子数破坏的约束

▲ 作者：CUORE COLLABORATION

▲链接：

https://www.science.org/doi/10.1126/science.adp6474

▲摘要：

人们生活在一个物质（相对于反物质）过多的世界。能够解释这种不平衡的理论之一是假设轻子数不守恒。无中微子双贝塔衰变是体现轻子数破坏的一个过程，在这个过程中，原子核内的两个中子转变为两个质子并释放两个电子，但不释放中微子。

低温地下稀有事件观测站（CUORE）合作组利用位于地下实验室的988个低温量热器系统，在一种碲同位素中搜寻了这种衰变。经过多年的数据积累，虽未发现具有统计显著性的衰变证据，但研究者成功改进了对该过程半衰期的约束。

▲ Abstract：

We live in a world with too much matter (as opposed to antimatter). One of the theories that can account for this imbalance posits that the lepton number is not conserved. A process that illustrates lepton number violation is the so-called neutrinoless double beta decay, in which two neutrons inside a nucleus turn into two protons and release two electrons but no neutrinos. The Cryogenic Underground Observatory for Rare Events (CUORE) collaboration searched for this decay in an isotope of tellurium using a system of 988 cryogenic calorimeters housed in an underground facility. Several years’ worth of data yielded no statistically significant evidence of the decay, but Bucci et al. succeeded in improving the constraints on the half-life for this process.

化学Chemistry

Biocatalytic, asymmetric radical hydrogenation of unactivated alkenes

非活化烯烃的生物催化不对称自由基氢化

▲ 作者：JAICY VALLAPURACKAL, RAJIB MANDAL, JUSTIN BOSSENBROEK, ARIS V. RUBIO, ETHAN POLADIAN, JAMES D. COLLINGS, CESAR TORRES, MATTHEW HENDRICKSON, JULIAN MORALES, AND SOUMITRA V. ATHAVALE

▲链接：

https://www.science.org/doi/10.1126/science.aea4737

▲摘要：

烯烃氢化是化学合成的核心反应之一，但酶促策略至今仍局限于通过氢负离子转移还原缺电子底物。研究利用血红素酶，为非活化烯烃的不对称还原开辟了一条氢化新途径。活性位点中硅烷促进的血红素-半胱氨酸氧化还原循环，可催化连续氢原子转移，作用于具有挑战性的分子骨架，包括1,1-二取代以及三、四取代烯烃。

进化后的酶具有底物宽泛性、氧气耐受性，使用地球上储量丰富的铁，并能在常温常压下进行克级规模反应。正交的氢原子来源可实现位点发散的不对称同位素标记。机理与计算研究支持逐步自由基过程。研究为立体选择性烯烃还原引入了生化新策略，并为下一代生物催化氢化提供了平台。

▲ Abstract：

Alkene hydrogenation is a cornerstone of chemical synthesis, yet enzymatic strategies remain limited to electron-deficient substrates by means of hydride transfer. Using heme enzymes, we unlock a hydrogenation pathway for the asymmetric reduction of unactivated olefins. A silane-promoted heme-cysteine redox cycle in the active site catalyzes sequential hydrogen atom transfer to challenging scaffolds, including 1,1-disubstituted as well as tri- and tetrasubstituted alkenes. The evolved enzymes are promiscuous and oxygen tolerant, use Earth-abundant iron, and can operate on the gram scale under ambient conditions. Orthogonal hydrogen atom sources enable site-divergent asymmetric isotope labeling. Mechanistic and computational studies support a stepwise radical process. Our work introduces a biochemical approach for stereoselective olefin reduction and provides a platform for next-generation biocatalytic hydrogenation.

A stoichiometrically conserved homologous series with infinite structural diversity

化学计量守恒且结构多样性无限的同系物系列

▲ 作者：HENGDI ZHAO, XIUQUAN ZHOU, ZILIANG WANG, PATRICIA E. MEZA, YIHAO WANG, DENIS T. KEANE, STEVEN J. WEIGAND, SAUL H. LAPIDUS, DUCK-YOUNG CHUNG, AND MERCOURI G. KANATZIDIS

▲链接：

https://www.science.org/doi/10.1126/science.aea8088

▲摘要：

由BaSbQ?晶体（Q为硫或碲）组成的系列化合物已被合成，其结构多样性直接由硫/碲比例的系统性调控所驱动。

研究者合成了至少10种这类“化学计量同形体”。它们由岩盐碎片层与碲化物曲折链交替堆叠构成。每个成员仅在这些结构单元的大小和组装方式上存在差异，而最终形成的晶相取决于阴离子电子亲和力及尺寸的差异。

▲ Abstract：

A series of BaSbQ? crystals (where Q is sulfur or tellurium) has been synthesized, and its structural diversity is directly driven by systematically varying the S/Te ratio. Zhao et al. synthesized at least 10 of these “stoichiomorphs” composed of rocksalt slab fragments stacked together with polytelluride zigzag chains. Each member differed only in the size and assembly of these blocks, and the crystal phase that resulted depended on differences in anion electron affinity and sizes.

生命科学Life Science

Cell wall patterning regulates plant stem cell dynamics

细胞壁模式调控植物干细胞动态

▲ 作者：XIANMIAO ZHU, XING CHEN, YANGXUAN LIU, YIMIN ZHU, GESHUANG GAO, MIAO LAN, YIHAO FU, YIMIN GU, HAN HAN, AND WEIBING YANG

▲链接：

https://www.science.org/doi/10.1126/science.ady4102

▲摘要：

植物细胞被包裹在半刚性的细胞壁中，细胞壁随细胞扩张而重构。果胶作为细胞壁的关键组分，其化学与材料特性可影响细胞分裂。研究者发现新细胞壁与成熟细胞壁的果胶特性存在差异，这些差异受果胶修饰酶（如PME5）调控。

他们证实PME5 RNA被RNA结合蛋白隔离在细胞核内，当细胞分裂末期核膜破裂时，PME5信使RNA（mRNA）被释放至细胞质。通过空间调控PME5 mRNA，果胶修饰的时机得以精确控制，从而与新生细胞分裂板的形成同步。

▲ Abstract：

Plant cells are wrapped in a semirigid wall that reconfigures as cells expand. The chemical and material properties of pectin, a key component of cell walls, can influence cell division. Zhu et al. found different pectin properties in new versus mature cell walls, which are controlled by pectin-modifying enzymes such as PME5. The authors established that PME5 RNA is sequestered in the nucleus by RNA-binding proteins. The PME5 messenger RNA (mRNA) is released into the cytoplasm during cytokinesis when the nuclear envelope breaks down. By spatially controlling PME5 mRNA, modification of pectin can be precisely timed to coincide with the formation of new cell division plates.

High-fidelity human chromosome transfer and elimination

高保真人类染色体转移与消除

▲ 作者：GIANLUCA PETRIS, SIMONA GRAZIOLI, LINDA VAN BIJSTERVELDT, PIERRE MURAT, KIM C. LIU, JAKOB BIRNBAUM, JULIAN E. SALE, AND JASON W. CHIN

▲链接：

https://www.science.org/doi/10.1126/science.adv9797

▲摘要：

合成人类基因组及其他千兆碱基级基因组需要新策略。研究实现了构建合成人类染色体流程中的关键步骤。

研究者建立了：（一）将人类染色体从人类细胞便捷转移至小鼠胚胎干细胞（组装细胞），使其在此处于单倍体状态、非必需且可被操作；（二）将这些人类染色体从单染色体杂合细胞转回人类细胞，以产生明确的合成性非整倍体；（三）消除对应的内源性人类染色体，从而再生含有转移染色体的二倍体细胞。

所有步骤均在非转化细胞中完成，未引发染色体碎裂，且产生的结构变异、插入、缺失或单核苷酸变异极少。

▲ Abstract：

The synthesis of human genomes and other gigabase-scale genomes will require new strategies. Here, we realized key steps in our pipeline for building synthetic human chromosomes. We established: (i) the facile transfer of human chromosomes from human cells to mouse embryonic stem cells (assembly cells), where they are haploid, are nonessential, and may be operated on; (ii) the transfer of these human chromosomes from monochromosomal hybrids back into human cells to generate defined, synthetic aneuploidies; and (iii) the elimination of the corresponding endogenous human chromosomes to regenerate diploid cells containing a transferred chromosome. All steps were performed in nontransformed cells without chromothripsis and generated minimal structural variants, insertions, deletions, or single-nucleotide variants.