Chromophore-Assisted Proximity Labeling of DNA Reveals Chromosomal Organization in Living Cells

The spatial arrangement of chromosome within the nucleus is linked to genome function and gene expression regulation. Existing genome-wide mapping methods often rely on chemically crosslinking DNA with protein baits, which raises concerns of artifacts being introduced during cell fixation. By genetically targeting a photosensitizer protein to specific subnuclear locations, we achieved blue-light-activated labeling of local DNA with a bioorthogonal functional handle for affinity purification and sequence identification through next-generation sequencing. When applied to the nuclear lamina in human embryonic kidney 293T cells, it revealed lamina-associated domains (LADs) that cover 37.6 % of the genome. These LADs overlap with heterochromatin hallmarks and are depleted with CpG islands. This simple labeling method avoids the harsh treatment of chemical crosslinking and is generally applicable to the genome-wide high-resolution mapping of the spatial chromosome organization in living cells.     

Divergent Total Synthesis of Euphoranginol C,Euphoranginone D,ent-Trachyloban-3β-ol,ent-Trachyloban-3-one,Excoecarin E,and ent-16α-Hydroxy-atisane-3-one

A divergent synthetic approach to biogenetically related diterpenoids such as ent-kauranes, ent-trachylobanes, ent-beyerane, and ent-atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]-octane moiety of ent-kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.0^2,7]-tricyclic core of ent-trachylobane and regioselective cyclopropane fragmentation furnishing ent-beyerane and ent-atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol.     

Bridge Bonded Oxygen Ligands between Approximated FeN4 Sites Confer Catalysts with High ORR Performance

The applications of the most promising Fe—N–C catalysts are prohibited by their limited intrinsic activities. Manipulating the Fe energy level through anchoring electron‐withdrawing ligands is found effective in boosting the catalytic performance. However, such regulation remains elusive as the ligands are only uncontrollably introduced oweing to their energetically unstable nature. Herein, we report a rational manipulation strategy for introducing axial bonded O to the Fe sites, attained through hexa‐coordinating Fe with oxygen functional groups in the precursor. Moreover, the O modifier is stabilized by forming the Fe?O?Fe bridge bond, with the approximation of two FeN₄ sites. The energy level modulation thus created confers the sites with an intrinsic activity that is over 10 times higher than that of the normal FeN₄ site. Our finding opens a novel strategy to manage coordination environments at an atomic level for high activity ORR catalysts.     

基于FDM-DEM耦合的冲击损伤大理岩静态断裂力学特征研究

为探究循环冲击损伤后大理岩的静态断裂力学特征,基于有限差分（finite difference method,FDM）-离散元（discrete element method,DEM）耦合的建模技术构建了三维分离式霍普金森压杆（split Hopkinson pressure bar,SHPB）数值模型,其中杆件系统和岩石试件分别采用FLAC3D和PFC3D程序建模。利用该模型对中心直切槽半圆盘（NSCB）试样进行了恒定子弹速度下的循环冲击,随后对受损试样进行静态三点弯曲断裂实验。通过编写Fish程序,提取试样断裂面数据,对断裂面进行重构并定量计算表面粗糙度。通过与相关室内实验结果的对比分析,验证了本文数值分析的合理性与可靠性。模拟结果表明,随着循环冲击次数的增加,试样内部微裂纹、破碎颗粒均增加。连接力场分布混乱,部分力链发生断裂。力链的变化是试样力学性能劣化的根本原因。在静态三点弯曲断裂实验中,冲击5次后试样的静态断裂韧度较天然试样产生一定程度的降低。试样在静载过程中产生的微裂纹和碎块的数量随循环冲击次数的增加而增加,断裂面粗糙度随循环冲击次数的增加而增加。     

关注青少年科学工作室

在回顾青少年科学工作室的发展历史,以及对青少年科学工作室的界定和宗旨进行探讨的基础上,本文以对近百个青少年科学工作室的深入调查为依据,力图全面、客观地描绘出我国校外青少年科学工作室的现状和作用,及其未来的发展方向。     

Secondary Metabolites from Hericium erinaceus and Their Anti-Inflammatory Activities

Hericium erinaceus, a culinary and medicinal mushroom, is widely consumed in Asian countries. Chemical investigation on the fruiting bodies of Hericium erinaceus led to the isolation of one new ergostane-type sterol fatty acid ester, erinarol K (1); and eleven known compounds: 5α,8α -epidioxyergosta-6,22-dien-3β-yl linoleate (2); ethyl linoleate (3); linoleic acid (4); hericene A (5); hericene D (6); hericene E (7); ergosta-4,6,8(14),22-tetraen-3-one (8); hericenone F (9); ergosterol (10); ergosterol peroxide (11); 3β,5α,6α,22E-ergosta-7,22-diene-3,5,6-triol 6-oleate (12). The chemical structures of the compounds were determined by 1D and 2D NMR (nuclear magnetic resonance) spectroscopy, mass spectra, etc. Anti-inflammatory effects of the isolated aromatic compounds (5–7, 9) were evaluated in terms of inhibition of pro-inflammatory mediator (TNF-α, IL-6 and NO) production in lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophage cells. The results showed that compounds 5 and 9 exhibited moderate activity against TNF-α (IC₅₀: 78.50 μM and 62.46 μM), IL-6 (IC₅₀: 56.33 μM and 48.50 μM) and NO (IC₅₀: 87.31 μM and 76.16 μM) secretion. These results supply new information about the secondary metabolites of Hericium erinaceus and their anti-inflammatory effects.     

软机器人的运动行为研究进展

软机器人的出现不仅弥补了传统机器人的缺点,并逐渐成为机器人领域的热点和前沿之一,近年来该领域研究进展十分迅速。本文总结了典型软机器人的运动行为的研究进展,介绍了软机器人按材质类型的分类(包括液晶软机器人、生物分子软机器人、PDMS软机器人、液体软机器人和自振荡凝胶软机器人)及其功能和潜在应用,讨论了当前不同类别软机器人运动的特点和存在的问题,在此基础上展望了软机器人领域面临的机遇、挑战和未来发展方向。     

碳纳米管负载钯基催化剂催化氧化2,5-呋喃二甲醇合成2,5-呋喃二甲酸

为积极应对化石能源枯竭和生态环境日益严峻等问题,可再生生物质资源的深度开发并进一步替代传统能源或石化原料被广泛认可.利用高效催化技术将生物质资源转化为高附加值的平台化合物,有望衍生出大量具备新颖结构与功能的绿色化学品.2,5-呋喃二甲酸(FDCA)作为重要的生物质基平台化合物之一,具有巨大的市场应用价值,其中因其与化石基对苯二甲酸(PTA)有着极其相似的化学结构,以FDCA替代PTA作为合成单体制备大宗聚合物备受关注.以5-羟甲基糠醛(HMF)为原料,采用多相催化体系(主要是贵金属催化剂)选择氧化制备FDCA是目前广泛采用的方法.但“HMF路线”面临一些基础性的难题,如HMF熔点较低,需低温存储,增加了实际应用中的运输成本;HMF在碱性溶液中易降解,导致反应过程中碳平衡损失;HMF结构中含有的不对称的羟基和醛基官能团在氧化反应中会发生竞争反应,致使反应副产物较多;此外,碱性反应介质中通常会得到醛基优先氧化的中间体5-羟甲基-2-呋喃甲酸(HMFCA),但由于HMFCA结构中羧基官能团的存在使得羟基进一步氧化较为困难,通常需要增加碱浓度、提升温度或压力,使反应条件变得苛刻.因此,寻求新的原料替代HMF,实现温和条件下高效合成FDCA具有重要意义.本文采用改性后的碳纳米管负载Pd催化剂(Pd/o-CNT),从具有独特对称结构的2,5-二羟甲基呋喃(BHMF)出发,提出一种新颖、高效催化合成FDCA的“BHMF路线”.反应在60°C常压下进行,BHMF在20 min内即可完全转化,60 min后FDCA的产率最高可达93.0%,优于相同条件下HMF为原料时的性能(FDCA产率仅为35.7%).相比于未作处理的碳纳米管负载钯催化剂(Pd/CNT),Pd/o-CNT催化剂具有更高含量的氢化钯(PdH_x)物种,显著促进了FDCA产率的提升.Pd/o-CNT在循环使用10次后,BHMF仍能完全转化,FDCA产率维持在75%.稳定性下降可能与活性物种流失、团聚及价态变化有关.基于对照试验,本文提出了可能的反应路径,即BHMF主要是通过2,5-二甲酰基呋喃和5-甲酰基-2-呋喃甲酸作为过程中间体,有效转化为FDCA,从而规避并减少生成HMF和活性较低的HMFCA.本文通过以新原料BHMF作底物,实现了高效制备生物基平台化合物FDCA,为生物质的产业化应用提供了新的研究思路.     

Au/SBA-15 的制备及其催化 CO 氧化反应性能

 以 SBA-15 为载体, 采用沉积沉淀法制备了纳米 Au 催化剂, 研究了不同预处理条件对 Au 在载体表面状态的影响, 考察了催化剂样品催化 CO 氧化性能. 以高分辨率透射电子显微镜、N2 吸附、X 射线衍射、紫外-可见漫反射吸收谱、X 射线光电子能谱和电感耦合等离子体发射光谱等手段对催化剂的结构和表面性质进行了表征. 结果表明, 经还原焙烧处理后的 Au/SBA-15 催化剂热稳定性较好, Au 在 SBA-15 孔道表面呈高分散状态, 样品在 CO 氧化反应中表现出优异的低温催化活性和高温稳定性, 同时具有优异的抗烧结性能和良好的循环稳定性.     

琥乙红霉素分子印迹聚合物微球的制备及表征

以琥乙红霉素为模板分子,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,采用悬浮聚合法制备得到了平均粒径约为60μm的琥乙红霉素分子印迹聚合物微球(MIPs),并用扫描电镜对其表面形貌进行了表征。考察了琥乙红霉素分子印迹聚合物的印迹效果,研究了琥乙红霉素分子印迹聚合物的动力学吸附特性。比较了MIPs对琥乙红霉素及其它3种抗生素的吸附情况。结果表明,制备得到的琥乙红霉素分子印迹聚合物微球对琥乙红霉素具有最好的吸附能力,显示出MIPs具有高的选择性。