Rational Development of Remote C−H Functionalization of Biphenyl: Experimental and Computational Studies

A simple and efficient nitrile‐directed meta‐C?H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U‐shaped template to achieve a molecular U‐turn and assemble the large‐sized cyclophane transition state for the remote C?H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta‐C?H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta‐selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand‐containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta‐selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non‐directed meta‐C?H activation. Substituted 2‐pyridone ligands were found to be key in assisting the cleavage of the meta‐C?H bond in the concerted metalation–deprotonation (CMD) process.     

Rapid measurements of curcumin from complex samples coupled with magnetic biocompatibility molecularly imprinted polymer using electrochemical detection

Curcumin widely exists in food, and rapid selective and accurate detection of curcumin have great significance in chemical industry. In this experiment, a new magnetic biocompatibility molecularly imprinted polymer was prepared with nontoxic and biocompatible Zein to adsorb curcumin selectively. The polymer has high biocompatibility, good adsorption capacity, and specific adsorption for curcumin. Combined with portable electrochemical workstations, the polymer can be used to detect curcumin rapidly and cost‐effectively. Using curcumin as a template and Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃O₄ particles for solid phase extraction. The experimental results showed that the polymer reached large adsorption capacity (32.12 mg/g) with fast kinetics (20 min). The adsorption characteristic of the polymer followed the Langmuir isotherm and pseudo‐second‐order kinetic models. Hexacyanoferrate was used as electrochemical probe to generate signals, and the linear range was 5–200 µg/mL for measuring curcumin. The experimental analysis showed that the polymer was an ideal material for selective accumulation of curcumin from complex samples. This approach has been successfully applied to the determination of curcumin in food samples with electrochemical detection, indicating that this is a feasible and practical technique.     

用光波导光模光谱技术研究DNA-DNA结合蛋白相互作用

探讨了应用光波导光模光谱(Optical waveguide lightmode spectroscopy,OWLS)技术研究DNA-DNA结合蛋白相互作用的可行性和灵敏性。以固定在传感器芯片表面的DNA探针为捕捉分子,溶液中同时含有探针结合序列和NF—κB结合位点序列的寡核苷酸与NF-κB亚单位p50同源二聚体形成的DNA-蛋白质复合物为检测分子,用光波导光模光谱检测技术建立非标记DNA-DNA结合蛋白相互作用检测研究体系。利用这一体系对不同样品中NF-κB p50浓度和具不同NF-κB结合位点序列的寡核苷酸与NF-κB p50亲合和力进行检测。样品中低至0．33 nmol/1的NF-κB p50被光波导光模光谱检测出,不同的NF-κB结合序列与NF-κB p50亲合力有显著的差异。研究发现,光波导光模光谱技术可以用于DNA-DNA结合蛋白相互作用研究,所建立的非标记检测研究体系可以进行样品中结合蛋白含量高灵敏检测和核酸序列与结合蛋白的亲合力的检测研究。     

One‐Pot Synthesis of 2,5‐Furandicarboxylic Acid from 2‐Furoic Acid by a Pd‐catalyzed Bromination–Hydroxycarbonylation Tandem Reaction in Acetate Buffer

The one‐pot synthesis of 2,5‐furandicarboxylic acid from 2‐furoic acid with a yield of 57 % was achieved for the first time using a Pd‐catalyzed bromination‐hydroxycarbonylation tandem reaction in HOAc‐NaOAc buffer. This synthetic protocol shows major improvements compared to previously reported methods, such as using biomass‐based 2‐furoic acid as low‐cost raw material, one‐pot synthesis without isolation of intermediate products, and no need for an acidification procedure. Experiments indicate that the involved Xantphos‐modified Pd‐catalyst and the buffer solution play significant promoting roles for each individual reaction whereas Br₂ (as the brominating reagent) had a negative effect on the second hydroxycarbonylation step, while CO was deleterious for the first bromination step. Hence, in this practical one‐pot synthesis, Br₂ should be consumed in the first bromination step as fully as possible, and CO is introduced after the first bromination step has been completed.     

二维导电金属有机骨架材料

金属有机骨架(MOFs)是由金属离子或簇与有机配体以配位键组装而成的晶态多孔材料,其高的孔隙率及功能可设计性使其广泛应用于各种领域.然而,传统MOFs多数电导率非常低,这严重制约了其在电学相关领域的发展.近年来,导电金属有机骨架尤其是二维导电金属有机骨架(2D ECMOFs)材料因其结构中独特的π-π堆积及π-d共轭作...     

求解参数识别反问题的同伦正则化方法

提出了求解参数识别反问题的同伦正则化方法,给出了相应的收敛性定理.数值结果表明该方法是一种快速的大范围收敛方法.     

用神经网络鉴别退化图像的模糊类型

提出了一种用神经网络鉴别退化图像的模糊类型的方法。由于采用不同降质方法得到退化图像的频谱差异较大,以此作为判别依据,用概率神经网络实现了对四种模糊类型:离焦,矩形,运动和高斯模糊的鉴别。根据神经网络的鉴别结果决定点扩散函数的初始估计值,可大大地提高盲解恢复算法的复原质量和系统点扩散函数的估计精度,扩大了算法的实用范围。     

对流层夜间化学研究

NO3自由基与N2O5是对流层夜间化学的关键物种。一方面NO3与O3等组分是夜间大气中的重要氧化剂,与它们的反应是生物排放挥发性有机物（VOCs）的主要汇;另一方面NO3与N2O5和雨滴或气溶胶颗粒物发生的异相反应则是大气中氮氧化合物NOx（NO,NO2）的主要清除过程,从而可以减轻对流层臭氧污染。研究它们的化学反应性质及对其进行实地测量,对深入理解大气氧化过程和全面了解区域乃至全球大气自净能力有重要意义。本文总结了近年来有关夜间化学的研究成果,介绍了以NO3和N2O5为中心的基本夜间化学过程、对流层中NO3与N2O5的源与汇以及外场测量技术的最新研究进展,并提出了尚待解决的一些问题。     

Characterisation of Flavour Attributes in Egg White Protein Using HS-GC-IMS Combined with E-Nose and E-Tongue: Effect of High-Voltage Cold Plasma Treatment Time

Egg white protein (EWP) is susceptible to denaturation and coagulation when exposed to high temperatures, adversely affecting its flavour, thereby influencing consumers’ decisions. Here, we employ high-voltage cold plasma (HVCP) as a novel nonthermal technique to investigate its influence on the EWP’s flavour attributes using E-nose, E-tongue, and headspace gas-chromatography-ion-mobilisation spectrometry (HS-GC-IMS) due to their rapidness and high sensitivity in identifying flavour fingerprints in foods. The EWP was investigated at 0, 60, 120, 180, 240, and 300 s of HVCP treatment time. The results revealed that HVCP significantly influences the odour and taste attributes of the EWP across all treatments, with a more significant influence at 60 and 120 s of HVCP treatment. Principal component analyses of the E-nose and E-tongue clearly distinguish the odour and taste sensors’ responses. The HS-GC-IMS analysis identified 65 volatile compounds across the treatments. The volatile compounds’ concentrations increased as the HVCP treatment time was increased from 0 to 300 s. The significant compounds contributing to EWP characterisation include heptanal, ethylbenzene, ethanol, acetic acid, nonanal, heptacosane, 5-octadecanal, decanal, p-xylene, and octanal. Thus, this study shows that HVCP could be utilised to modify and improve the EWP flavour attributes.     

Peridynamic modeling and simulation of coupled thermomechanical removal of ice from frozen structures

Meccanica - In this work, a bond-based peridynamic de-icing model has been developed to simulate the thermo-mechanical ice removal process of frozen structures. In the proposed numerical method,...