o‐Fluorination of Aromatic Azides Yields Improved Azido‐Based Fluorescent Probes for Hydrogen Sulfide: Synthesis,Spectra, and Bioimaging

Hydrogen sulfide (H₂S) is an endogenously produced gaseous signaling molecule with multiple biological functions. To visualize the endogenous in situ production of H₂S in real time, new coumarin‐ and boron‐dipyrromethene‐based fluorescent turn‐on probes were developed for fast sensing of H₂S in aqueous buffer and in living cells. Introduction of a fluoro group in the ortho position of the aromatic azide can lead to a greater than twofold increase in the rate of reaction with H₂S. On the basis of o‐fluorinated aromatic azides, fluorescent probes with high sensitivity and selectivity toward H₂S over other biologically relevant species were designed and synthesized. The probes can be used to in situ to visualize exogenous H₂S and D ‐cysteine‐dependent endogenously produced H₂S in living cells, which makes them promising tools for potential applications in H₂S biology.     

Synthesis of optically active poly(N‐propargylsulfamides) with helical conformation

A novel chiral N‐propargylsulfamide monomer ( 1a ) and its enantiomer ( 1b ) were synthesized and polymerized with (nbd)Rh⁺B^?(C₆H₅)₄ as a catalyst providing poly(1) (poly( 1a ) and poly( 1b )) in high yields (≥99%). Poly(1) could take stable helices in less polar solvents (chloroform and THF), demonstrated by strong circular dichroism signals and UV–vis absorption peaks at about 415 nm and the large specific rotations; but in more polar solvents including DMF and DMSO, poly(1) failed to form helix. Quantitative evaluation with anisotropy factor showed that the helical screw sense had a relatively high thermal stability. These results together with the IR spectra measured in solvents showed that hydrogen bonding between the neighboring sulfamide groups is one of the main driving forces for poly(1) to adopt stable helices. In addition, copolymerization of monomer 1a and monomer 2 was conducted, the solubility of poly(1) was improved drastically. However, the copolymerization had adverse effects on the formation of stable helices in the copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 500–508, 2007     

Multi‐Fluorinated Azido Coumarins for Rapid and Selective Detection of Biological H2S in Living Cells

Hydrogen sulfide (H₂S) is an endogenously produced gaseous signaling molecule with multiple biological functions. In order to visualize the endogenous in situ production of H₂S in living cells in real time, here we developed multi‐fluorinated azido coumarins as fluorescent probes for the rapid and selective detection of biological H₂S. Kinetic studies indicated that an increase in fluorine substitution leads to an increased rate of H₂S‐mediated reduction reaction, which is also supported by our theoretical calculations. To our delight, tetra‐fluorinated coumarin 1 could react with H₂S fast (t_1/2≈1 min) and selectively, which could be further used for continuous enzymatic assays and for visualization of intracellular H₂S. Bioimaging results obtained with 1 revealed that d ‐Cys could induce a higher level of endogenous H₂S production than l ‐Cys in a time‐dependent manner in living cell.     

ANIONIC POLYMERIZATION OF ALKYL METHACRYLATES INITIATED BY nBuCu(NCy2)Li

Anionic polymerization of methyl methacrylate(MMA),n-butyl methacrylate(nBMA)and glycidyl methacrylate (GMA)initiated by nBuCu(NCy_2)Li(1)in tetrahydrofuran(THF)at-50℃to-10℃was investigated.It was found that the polymerization of MMA and nBMA initiated by 1 proceeded quantitatively in THF to afford PMMA and PBMA with polydispersity index 1.15-1.30 and nearly 100%initiator efficiencies at-10℃.The molecular weights increased linearly with the ratio of[monomer]/[1].However,a post-polymerization experiment c...     

A leap forward in sulfonium salt and sulfur ylide chemistry

Sulfonium salts and sulfur ylides are important S(Ⅳ) motifs,and have displayed many unique reactivities to provide simple,effective,and often stereoselective synthesis toward sulfur containing compounds.Impressive developments have been witnessed within this field during the past several years.In light of the increasing demand of organosulfur compounds across the range of chemical sciences,our aim of this review is to provide a concise overview of recent advances of sulfonium salt and sulfur ylide chemistry.Selected examples are organized in three parts on the basis of their role in organic reactions(reactants,intermediates and catalysts).     

Chemoselective Phototransformation of CH Bonds on a Polymer Surface through a Photoinduced Cerium Recycling Redox Reaction

It is generally accepted that Ce⁴⁺ is unable to directly oxidize unreactive alkyl C?H bonds without the assistance of adjacent polar groups. Herein, we demonstrate in our newly developed confined photochemical reaction system that this recognized issue may be challenged. As we found, when a thin layer of a CeCl₃/HCl aqueous solution was applied to a polymeric substrate and the substrate subjected to UV irradiation, Ce³⁺ was first photooxidized to form Ce⁴⁺ in the presence of H⁺, and the in situ formed Ce⁴⁺ then performs an oxidation reaction on the C?H bonds of the polymer surface to form surface‐carbon radicals for radical graft polymerization reactions and functional‐group transformations, while reducing to Ce³⁺ and releasing H⁺ in the process. This photoinduced cerium recycling redox (PCRR) reaction behaved as a biomimetic system in an artificial recycling reaction, leading to a sustainable chemical modification strategy for directly transforming alkyl C?H bonds on polymer surfaces into small‐molecule groups and polymer brushes. This method is expected to provide a green and economical tool for industrial applications of polymer‐surface modification.     

Study on boron and nitrogen co-doped graphene xerogel for high-performance electrosorption application

Journal of Solid State Electrochemistry - The search for highly efficient carbon materials with high desalting capacity for the brackish water desalination is still indispensable. In this study,...     

含2,2′,4-三(2-氯苯基)-5-(3,4-二甲氧基苯基)-4′,5′-二苯基-1,1′-双咪唑光引发体系的光聚合动力学研究

2,2′,4-三(2-氯苯基)-5-(3,4-二甲氧基苯基)-4′,5′-二苯基-1,1′-二咪唑(CZ-HABI)是一种高效的光引发剂,其结构通过傅里叶红外光谱仪、核磁共振仪、紫外吸收光谱进行表征.复合引发体系(PI)由光引发剂CZ-HABI、增感剂4,4′-双(二乙氨基)苯甲酮(EMK)、供氢体N-苯基甘氨酸(NPG)组成,利用实时红外(RT-IR)对该复合光引发体系进行了光聚合反应动力学研究,结果表明:在没有供氢体条件下,基本上没有引发效果,增加供氢体后,引发效率大幅增加;增加复合光引发体系用量能提高光聚合反应的双键转化率,且最大聚合速率与[PI]1/2成正比;随着光强的增强,单体的双键转化率与最大反应速率均增大;复合光引发体系引发双丙烯酸酯类单体的最终双键转化率比三丙烯酸酯类单体要高.复合光引发体系的引发效率比ITX/EDAB光引发体系的引发效率高,与1-羟基环己基苯基甲酮(184)、2-羟基-2-甲基-1-苯基-1-丙酮(1173)的引发效果相近.     

A Dual‐Response Fluorescent Probe Reveals the H2O2‐Induced H2S Biogenesis through a Cystathionine β‐Synthase Pathway

The two signaling molecules H₂S and H₂O₂ play key roles in maintaining intracellular redox homeostasis. The biological relationship between H₂O₂ and H₂S remains largely unknown in redox biology. In this study, we rationally designed and synthesized single‐ and dual‐response fluorescent probes for detecting both H₂O₂ and H₂S in living cells. The dual‐response probe was shown to be capable of mono‐ and dual‐detection of H₂O₂ and H₂S selectively and sensitively. Detailed bioimaging studies based on the probes revealed that both exogenous and endogenous H₂O₂ could induce H₂S biogenesis in living cells. By using gene‐knockdown techniques with bioimaging, the H₂S biogenesis was found to be majorly cystathionine β‐synthase (CBS)‐dependent. Our finding shows the first direct evidence on the biological communication between H₂O₂ (ROS) and H₂S (RSS) in vivo.     

Direct Utilization of Non-pretreated Hydrolytic Liquid of Dried Distiller’s Grains with Solubles for Bio-Ethanol by <Emphasis Type="Italic">Rhizopus arrhizus RH 7-13-9#</Emphasis>

Bio-ethanol, as an environment friendly and renewable fuel, has gained increasing worldwide attention and can be produced through the fermentation of the carbohydrates or sugar(s) fraction of biomass materials. Here, dried distiller’s grains with solubles (DDGS), a waste in production of bio-ethanol, were applied to prepare acid-hydrolytic liquid and it was directly used as seed culture and fermentation medium without pretreatment. Rhizopus arrhizus RH 7-13-9# cultured in non-pretreated acid-hydrolytic liquid with pH 4.7 for 30 h could utilize the concentrated hydrolytic liquid as well as the hydrolytic liquid mixed with glucose. A high yield of bio-ethanol was obtained. It was proven that common used medium could be replaced by non-pretreated acid-hydrolytic liquid to some extent. The pretreated process of acid-hydrolytic liquid was avoided that decreased feed stock cost and was significant for the utilization of acid-hydrolytic liquid from lignocellulose materials.