限域单分子层冰-水两相平衡体系的分子动力学模拟

限域水因有极其丰富的结构物相变化而成为近年来水科学研究的一个热点.然而,不同相限域水之间的相平衡结构与性质却鲜有报道.论文提出一套分子动力学模拟技术,可实现纳米尺度限域条件下冰和水的不同结构相间形成的低维固-液界面（线）的平衡态模拟.应用此模拟技术,我们探索了0.65 nm限域尺寸、5000 bar限域压强条件下,单分子层厚度的冰-水（固-液）两相平衡,计算了该平衡体系一系列热力学量在界线附近的分布.平衡态的分子模拟结果直观地展示了粗糙型固-液界线的热毛细涨落、界线固-液结构转变的微观机制、以及缺陷在固-液相变区附近的形成与输运.各种热力学量分布函数呈现了二维限域冰-水共存界面（线）的特殊性质,如：相平衡区域的尺寸异于块体材料固-液界面,固-液界线处于切向压缩状态等.     

量子阱单激子光增益实现超低阈值连续波激光

胶质纳米晶光增益材料对于开发新一代的高效激光器前景巨大.采用外延生长法制备原子尺寸厚度的Ⅱ型CdSe/CdTe复合纳米片,研究该异质结构的光学性质及其对应的电荷动力学过程,以此探讨其光增益性能及激光应用潜能.光谱结果表明,Ⅱ型纳米片有效的电子与空穴分离结构使其表现出较大的斯托克斯位移（△_S=100 meV）和较强的激子-激子库伦排斥力（△_XX=50 meV）.△_S和△_XX的协同效应使"激子-双激子"吸收能相比单激子发射能提高了约150 meV,打破了一般纳米晶结构中两者的简并关系,这将有效抑制光吸收损失并促进单激子光增益.单激子光增益机制下该纳米片较长的单激子寿命（τ_x=394 ns）使连续激光泵浦的理论功率阈值低至12 W/cm²,这为开发实用性更强的、超低阈值的连续波激光器提供可能.     

Chemical Biology Approaches for Investigating the Functions of Lysine Acetyltransferases

The side‐chain acetylation of lysine residues in histones and non‐histone proteins catalyzed by lysine acetyltransferases (KATs) represents a widespread posttranslational modification (PTM) in the eukaryotic cells. Lysine acetylation plays regulatory roles in major cellular pathways inside and outside the nucleus. In particular, KAT‐mediated histone acetylation has an effect on all DNA‐templated epigenetic processes. Aberrant expression and activation of KATs are commonly observed in human diseases, especially cancer. In recent years, the study of KAT functions in biology and disease has greatly benefited from chemical biology tools and strategies. In this Review, we present the past and current accomplishments in the design of chemical biology approaches for the interrogation of KAT activity and function. These methods and probes are classified according to their mechanisms of action and respective applications, with both strengths and limitations discussed.     

MoB/g‐C3N4 Interface Materials as a Schottky Catalyst to Boost Hydrogen Evolution

Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal–semiconductor junction principles is presented. With metallic MoB, the introduction of n‐type semiconductive g‐C₃N₄ induces a vigorous charge transfer across the MoB/g‐C₃N₄ Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec^?1 and a high exchange current density of 17 μA cm^?2, which is far better than that of pristine MoB. First‐principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation.     

An Aluminum–Sulfur Battery with a Fast Kinetic Response

The electrochemical performance of the aluminum‐sulfur (Al‐S) battery has very poor reversibility and a low charge/discharge current density owing to slow kinetic processes determined by an inevitable dissociation reaction from Al₂Cl₇^? to free Al³⁺. Al₂Cl₆Br^? was used instead of Al₂Cl₇^? as the dissociation reaction reagent. A 15‐fold faster reaction rate of Al₂Cl₆Br^? dissociation than that of Al₂Cl₇^? was confirmed by density function theory calculations and the Arrhenius equation. This accelerated dissociation reaction was experimentally verified by the increase of exchange current density during Al electro‐deposition. Using Al₂Cl₆Br^? instead of Al₂Cl₇^?, a kinetically accelerated Al‐S battery has a sulfur utilization of more than 80 %, with at least four times the sulfur content and five times the current density than that of previous work.     

Nickel(II)-catalyzed addition reaction of arylboronic acids to isatins

A Ni-catalyzed addition of arylboronic acids to isatins was first developed. The reaction, driven by Ni(acac)₂ and dppp as the phosphine ligand, gave 3-aryl-3-hydroxy-2-oxindoles in up to 97% yield. Scopes of benzyl-protected isatins and arylboronic acids were examined. Substituted phenylboronic acids along with fused-ring and heterocyclic boronic acids reacted with isatins smoothly. Preliminary asymmetric catalysis was investigated as well, showing moderate enantioselectivity. The mechanism was also described.     

One-pot ligation strategy for atypical ubiquitin chains synthesis by using the trifluoroacetamidomethyl-protected isopeptide-linked Ub (Tfacm-isoUb) unit

Protein chemical synthesis can provide the homogeneous atypical ubiquitin chains that are usually difficult to obtain by other methods. Herein, we report a new one-pot ligation approach for the synthesis of atypical Ub chains based on the Tfacm-protected isoUb building block with operational simplicity and high efficiency. The key intermediate, the Tfacm-protected isoUb building block can be readily prepared by Fmoc SPPS. The practicality and efficiency of the new method is demonstrated by the successful preparation of K11-linked di-Ub.     

超高效液相色谱-四极杆-飞行时间质谱法定性筛查保健食品中西地那非及其相关功效类非法添加化合物

建立了超高效液相色谱-四极杆-飞行时间质谱（UPLC-Q-TOF-MS）定性筛查102种西地那非及其相关功效化合物的方法。甲醇超声提取样品;采用Agilent Poroshell 120 SB-C18色谱柱（75 mm×3.0 mm,2.7 μm）,以0.1%（v/v）甲酸水溶液-乙腈为流动相梯度洗脱,流速0.4 mL/min;采用电喷雾离子（ESI）源,Q-TOF-MS作检测器,正离子模式检测;与对照品保留时间、母离子及碎片离子精确相对分子质量、元素组成比对,准确定性。西地那非等100种化合物在10种基质中的检出限为0.1~50 mg/kg或0.1~50 mg/L。并分类归纳了文中涉及的98种磷酸二酯酶5抑制剂质谱碎片裂解规律,为可疑物的识别和鉴定提供参考。该方法已应用于实际样品的测定,检出19种化合物,有效打击了非法添加行为。     

Selective Hydrogenation of CO2 to Ethanol over Cobalt Catalysts

Methods for the hydrogenation of CO₂ into valuable chemicals are in great demand but their development is still challenging. Herein, we report the selective hydrogenation of CO₂ into ethanol over non‐noble cobalt catalysts (CoAlO_x), presenting a significant advance for the conversion of CO₂ into ethanol as the major product. By adjusting the composition of the catalysts through the use of different prereduction temperatures, the efficiency of CO₂ to ethanol hydrogenation was optimized; the catalyst reduced at 600 ° gave an ethanol selectivity of 92.1 % at 140 °C with an ethanol time yield of 0.444 mmol g^?1 h^?1. Operando FT‐IR spectroscopy revealed that the high ethanol selectivity over the CoAlO_x catalyst might be due to the formation of acetate from formate by insertion of *CH_x, a key intermediate in the production of ethanol by CO₂ hydrogenation.     

Superoxide Stabilization and a Universal KO2 Growth Mechanism in Potassium–Oxygen Batteries

Rechargeable potassium–oxygen (K‐O₂) batteries promise to provide higher round‐trip efficiency and cycle life than other alkali–oxygen batteries with satisfactory gravimetric energy density (935 Wh kg^?1). Exploiting a strong electron‐donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO₂), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO‐based K‐O₂ battery demonstrates a much higher energy efficiency and stability than the glyme‐based electrolyte. A universal KO₂ growth model is developed and it is demonstrated that the ideal solvent for K‐O₂ batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K‐O₂ batteries.