室温下铜催化制备含羰基或酯基的喹唑啉-4(3H)-亚基类衍生物

在室温的条件下,建立了一种简单实用的铜催化制备含酮羰基或酯基的喹唑啉-4(3H)-亚基类衍生物的新方法.实验证明以2-溴苯甲酰乙酸甲酯类似物及脒盐酸盐为原料,碘化亚铜为催化剂,磷酸钾为碱,无添加配体的情况下,可成功制备一系列喹唑啉类衍生物.其结构均经1H NMR、13C NMR及HRMS确证.     

人工智能助力当代化学研究

以机器学习为代表的人工智能在当代的科学研究中正在发挥越来越重要的作用.不同于传统的计算机程序,机器学习人工智能可以通过对大量数据的反复分析和自身模型的优化,即“学习”过程,从而在大量的数据中寻找客观事物的相互联系,形成具有更好预测和决策能力的新模型,做出合理的判断.化学研究的特点恰恰是机器学习人工智能的强项.化学研究经常要面对十分复杂的物质体系和实验过程,从而很难通过化学物理原理进行精准的分析和判断.人工智能可以挖掘化学实验中产生的海量实验数据的相关性,帮助化学家做出合理分析预测,大大加速化学研发过程.本文介绍了当代人工智能方法及用其解决化学问题基本原理,并通过具体案例展示了人工智能辅助解决不同化学研发问题的方法以及对应的机器学习算法.将人工智能运用在化学科学的尝试正处于蓬勃上升期,人工智能已经初步展示出对化学研究的强大助力,希望本文能帮助更多的国内的化学工作者了解和运用这一有力的工具.     

Gasotransmitter Regulation of Phosphatase Activity in Live Cells Studied by Three‐Channel Imaging Correlation

Enzyme activity in live cells is dynamically regulated by small‐molecule transmitters for maintaining normal physiological functions. A few probes have been devised to measure intracellular enzyme activities by fluorescent imaging, but the study of the regulation of enzyme activity via gasotransmitters in situ remains a long‐standing challenge. Herein, we report a three‐channel imaging correlation by a single dual‐reactive fluorescent probe to measure the dependence of phosphatase activity on the H₂S level in cells. The two sites of the probe reactive to H₂S and phosphatase individually produce blue and green fluorescent responses, respectively, and resonance energy transfer can be triggered by their coexistence. Fluorescent analysis based on the three‐channel imaging correlation shows that cells have an ideal level of H₂S to promote phosphatase activity up to its maximum. Significantly, a slight deviation from this H₂S level leads to a sharp decrease of phosphatase activity. The discovery further strengthens our understanding of the importance of H₂S in cellular signaling and in various human diseases.     

D-π-A型三联吡啶衍生物的合成及光学性质

以4'-(4-甲苯基)-2,2'∶6',2″-三联吡啶为电子受体(A)基元, 通过Wittig反应引入电子给体(D)基元, 合成了2个新的D-π-A型三联吡啶衍生物; 研究了其单、 双光子吸收荧光特性, 并通过量子化学计算从结构角度进行了解释. 目标产物的荧光量子产率(Ф)最高达到0.45, 双光子吸收截面(δ₂)最大达406 GM.     

Thermal energy storage properties and thermal reliability of PEG/bone char composite as a form-stable phase change material

Journal of Thermal Analysis and Calorimetry - Bone char (BC) is a promising porous material that can be used for preparing a form-stable composite phase change material (PCM). In this paper,...     

聚苯乙烯-b-聚右旋乳酸二嵌段共聚物的热性能和结晶行为研究

合成了系列聚右旋乳酸(PDLA)嵌段重量分率(fw=0～0.61)的窄分子量分布聚苯乙烯-b-聚右旋乳酸二嵌段共聚物(PS-b-PDLA).运用温度调制示差扫描热分析仪(TMDSC)和热台偏振光显微镜(POM)等研究手段,对制备所得的结晶性二嵌段共聚物的热性能、结晶速率与结晶形貌等进行了研究.研究结果表明,与聚右旋乳酸均聚物相比,随着PS-b-PDLA中结晶性PDLA嵌段重量分率fw减少,无定形聚苯乙烯嵌段(PS)对PDLA嵌段链段的结晶抑制作用增强,PS-b-PDLA的热结晶性能与结晶形貌发生显著变化;相对于PDLA均聚物,PS-b-PDLA的冷结晶温度(Tcc)和结晶平衡熔点(Tm0)分别下降14℃和38℃,球晶生长速率明显降低.在无定形PS嵌段链段的玻璃化温度(Tg)附近,二嵌段PS-b-PDLA的结晶行为出现拐点,揭示PS嵌段由于相分离所形成纳米微相空间对PS-b-PDLA中PDLA链段的结晶产生影响,并且该影响作用程度与PDLA嵌段的重量分率fw和结晶温度(Tc)相关。     

Micromagnetic modeling studies on the effects of stress on magnetization reversal and dynamic hysteresis

The complex behaviors of magnetic materials subjected to magneto-electro-mechanical coupled fields call for a better understanding of the mechanism of multi-fields coupling. In this paper, micromagnetic modeling is carried out to study the effect of stress on hysteresis loops and dynamic magnetization reversal. The time-dependent Landau–Lifshitz–Gilbert equation which governs the evolution of magnetization is solved using the fast Fourier transform technique in reciprocal space. The simulation results show that the stress changes the distribution of easy directions and, therefore, leads to the change of magnetic properties. Moreover, the positive product of the stress and saturation magnetostriction coefficients increases the coercivity, hence, increases the area enclosed by the hysteresis loop. A stress-induced magnetization reversal is investigated.     

Inkjet printing lanthanide doped nanorods test paper for visual assays of nitroaromatic explosives

The facile and sensitive strategies for detections of nitroaromatic explosives are highly desirable in many challenging environments, especially for homeland security against terrorism. Here, we inkjet printed polyethylenimine (PEI)-coated Ce, Tb co-doped NaGdF₄ nanorods (NaGdF₄:Ce/Tb NRs) onto common filter paper to construct test paper for visual and instant detections of a typical explosive 2,4,6-trinitrophenol (TNP). Polyethylenimine molecules not only facilitate the formation of uniform NaGdF₄ nanorods but also provide specific recognized sites for TNP by the acid–base pairing interaction. The resultant TNP bound at the surface of PEI-coated NaGdF₄:Ce/Tb NRs can strongly quench the phosphorescence with a remarkably high quenching constant by the charge transfer mechanism from NaGdF₄:Ce/Tb NRs to TNP. By printing of the probe on a piece of filter paper, trace amounts of TNP can be visually detected by the appearance of a dark color against a bright green background under a UV lamp. This test paper can detect TNP as low as 0.45 ng mm⁻² by the naked eye, which provides a potential application in the rapid, on-line detections of explosives.     

A Multi‐responsive Fluorescent Probe Reveals Mitochondrial Nucleoprotein Dynamics with Reactive Oxygen Species Regulation through Super‐resolution Imaging

Understanding the biomolecular interactions in a specific organelle has been a long‐standing challenge because it requires super‐resolution imaging to resolve the spatial locations and dynamic interactions of multiple biomacromolecules. Two key difficulties are the scarcity of suitable probes for super‐resolution nanoscopy and the complications that arise from the use of multiple probes. Herein, we report a quinolinium derivative probe that is selectively enriched in mitochondria and switches on in three different fluorescence modes in response to hydrogen peroxide (H₂O₂), proteins, and nucleic acids, enabling the visualization of mitochondrial nucleoprotein dynamics. STED nanoscopy reveals that the proteins localize at mitochondrial cristae and largely fuse with nucleic acids to form nucleoproteins, whereas increasing H₂O₂ level leads to disassociation of nucleic acid–protein complexes.     

Amphiphilic cationic [dendritic poly(L-lysine)]-block-poly(L-lactide)-block-[dendritic poly(L-lysine)]s in aqueous solution: self-aggregation and interaction with DNA as gene delivery carriers

A new series of triblock [dendritic poly(L-lysine)]-block-PLLA-block-[dendritic poly(L-lysine)]s (DL(2) -PLLA-DL(2) ) with PLLA block lengths of 11.5-26.5 and double 2-generation PLL dendrons DL(2) as model cationic amphiphiles were synthesized and characterized. Their CAC, self-aggregation and plasmid DNA binding affinities in pure water and PBS were studied. The PLLA block length dependence of particle size, morphology and ξ potential for organized pDNA/amphiphile polyplex aggregates were examined. Finally, toxicities of these DL(2) -PLLA-DL(2) amphiphiles and their polyplexes were assayed by MTT with HeLa, SMMC-7721 and COS-7 cells, and COS-7 cell luciferase and eGFP gene transfection efficacies with these amphiphiles as the delivery carriers were investigated.