Intermolecular Couplization and Cyclization of Chalcones Promoted by Samarium in DMF

Under mild and neutral conditions, reductive coupling–cyclization of chalcones was promoted by samarium metal with an activator in DMF to afford products in good to excellent yields. The reaction is regioselective over the competitive carbon–carbon double-bond reduction and stereocontrolled.     

Different processes responsible for blue pumped, ultraviolet and violet luminescence in high-concentrated Er:YAG and low-concentrated Er:YAP crystals

Ultraviolet and violet upconverted luminescence in high-concentrated (8.4 at%) Er³⁺:YAG and low-concentrated (1 at%) Er³⁺:YAP crystals has been investigated under blue laser excitation of the ⁴F_7/2 multiplet. The upconversion mechanisms were studied in detail based on upconversion luminescence intensity dependence and decay curves. Upconversion luminescence was attributed to energy transfer processes in Er³⁺:YAG and excited state absorption processes in Er³⁺:YAP, respectively.     

一种力-电协同驱动的细胞微流控培养腔理论模型

细胞培养液在微流控生物反应器中受到外界物理场（如压力梯度或者电场）作用流动而产生流体剪应力,并进一步刺激种子细胞调控其内部基因的表达,从而促进细胞的分化和生长,这个过程在自然生命组织内的微管中亦是如此。考虑到细胞培养微腔隙中液体流动行为很难实验量化测定,理论建模分析是目前可行的研究手段。因此建立了矩形截面的细胞微流控培养腔理论模型,将外部的物理驱动场（压力梯度与电场）与培养腔内液体的流速、切应力和流率联系起来,分别得到了压力梯度驱动（Pressure gradient driven,PGD）、电场驱动（Electric field driven,EFD）及力-电协同驱动（Pressure-electricity synergic driven,P-ESD）三种驱动方式下的液体流动理论模型。结果表明该理论模型与现有的实验结果基本一致,具体地:力-电协同作用下的解答为压力梯度驱动和电场驱动结果的叠加。细胞培养腔内的流体流速、剪应力及流率幅值均正比于外部物理场强幅值,但随着压力梯度驱动载荷频率的增大而减小,随着电场驱动频率的变化不明显。在压力梯度驱动作用下,细胞贴壁处的切应力随着腔高的增大而线性增大,流率则随着腔高的增大而非线性增大,而电场驱动下的结果不受腔高的影响。生理范围内的温度场变化对压力和电场驱动的结果影响不大。另外,在引起细胞响应的流体切应力水平,电场驱动能提供较大的切应力幅值而压力梯度驱动则能提供较大的流率幅值。该理论模型的建立为细胞微流控生物反应器实验系统的设计及参数优化提供理论参考,同时也为力-电刺激细胞生长、分化机理的研究的提供基础。      

Dynamics of excited state relaxation and frequency upconversion in Tm3+ and Tm3+/Tb3+ doped ZBLAN glass

The effects of activator concentration on the relaxation of the ¹I₆, ¹D₂, ¹G₄ and ³H₄ levels of Tm³⁺ were investigated by the analysis of the fluorescence decay curves in Tm³⁺ and Tm³⁺/Tb³⁺ doped ZBLAN glasses. UV and blue upconversion luminescence bands around 362 and 450 nm were observed by 655 nm laser excitation in all the samples. The upconversion mechanism was attributed to excited state absorption (ESA) by analyzing the decay profiles and the intensity dependence.     

A Priori and A Posteriori Error Estimates of Streamline Diffusion Finite Element Method for Optimal Control Problem Governed by Convection Dominated Diffusion Equation

In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existence and uniqueness of the discretized scheme.Then a priori and a posteriori error estimates are derived for the state,the co-state and the control.Three numerical examples are presented to illustrate our theoretical results.     

Expanding the Promiscuity of a Copper-Dependent Oxidase for Enantioselective Cross-Coupling of Indoles

Herein, we disclose the highly enantioselective oxidative cross-coupling of 3-hydroxyindole esters with various nucleophilic partners as catalyzed by copper efflux oxidase. The biocatalytic transformation delivers functionalized 2,2-disubstituted indolin-3-ones with excellent optical purity (90–99 % ee), which exhibited anticancer activity against MCF-7 cell lines, as shown by preliminary biological evaluation. Mechanistic studies and molecular docking results suggest the formation of a phenoxyl radical and enantiocontrol facilitated by a suited enzyme chiral pocket. This study is significant with regard to expanding the catalytic repertoire of natural multicopper oxidases as well as enlarging the synthetic toolbox for sustainable asymmetric oxidative coupling.     

Highly Efficient Conversion of Homocoupling and Heterocoupling of Terminal Alkynes Catalyzed by AuCu24/AC-200

Regulation of Hybrid Materials of Ministry of Education, Bimetallic nanoclusters with synergistic effect exhibit better stability and activity than monometallic nanoclusters in catalytic applications. However, the large number of ligands on the surface of nanoclusters obscure the active sites, thus reducing the catalytic activity. Here, AuCu₂₄/AC−X (X=0, 200, 300, 500, 800) catalysts were fabricated by removing the partial ligands on the surface of AuCu₂₄H₂₂((p-FPh)₃P)₁₂ nanoclusters (short for AuCu₂₄ NCs), and investigated the influence of calcination temperature on catalytic performance of AuCu₂₄/AC in homocoupling and heterocoupling of terminal alkynes. The results showed that the catalytic activity of AuCu₂₄/AC−X exhibited a volcanic trend with the increase of X (heat treatment temperature) and the content of Cu²⁺ also changed with the increase of X. Compared with Au₂₅/AC-200 and Cu₂₅/AC-200 catalysts, the AuCu₂₄/AC-200 bimetallic catalyst showed the highest catalytic activity in homocoupling and heterocoupling of terminal alkynes under mild conditions with TOF values reaching 478.7 h⁻¹ and 114.1 h⁻¹ respectively, which are higher than most reported catalysts. This work provides a research idea for the design of bimetallic nanoclusters with superior performance.     

CuCoO2 Nanoparticles as a Nanoprotease for Selective Proteolysis with High Efficiency at Room Temperature

Many nanoproteases contain tetravalent metal ions and catalyze peptide-bond hydrolysis only at high temperature (60 °C). Here, we report a new and effective strategy to explore nanoproteases from nanoparticles containing low valent metal ions. We found that flower-like CuCoO₂ nanoparticles (CuCoO₂ NPs) containing low valent Cu⁺ possessed excellent catalytic activity towards selective cleavage of peptide bonds with hydrophobic residues in bovine serum albumin (BSA) at room temperature. CuCoO₂ NPs exhibited excellent stability and had great reusability. CuCoO₂ NPs also hydrolyzed heat-denatured and surfactant-denatured BSA. Mechanism analysis revealed that the high Lewis acidity of Co³⁺ and the low valence of Cu⁺ were both essential for the high protease activity of CuCoO₂ NPs. The flower-like structure of CuCoO₂ NPs and the strong nucleophilicity of Cu⁺-bound hydroxyl endow them with excellent catalytic performance. The findings open a new way for the design and discovery of high-efficiency nanoproteases.