“On‐Off” Multivalent Recognition: Degradable Dendrons for Temporary High‐Affinity DNA Binding

Now you bind it—now you don't! Chemical degradation of a dendritic scaffold allows multivalent interactions with DNA to be “switched off” as the multivalent array of ligands breaks down into smaller fragments, offering an approach by which a molecule can be temporarily endowed with high affinity for a biological target—an important concept in the development of new synthetic systems to intervene in biological pathways.

     

基于铱纳米棒的电致化学发光生物传感器用于多巴胺检测

铱(Ⅲ)配合物差的水溶性限制了其在电致化学发光(ECL)领域的应用.该文用聚(苯乙烯-马来酸酐)(PSMA)羧基功能化三(2-苯基吡啶)铱(Ⅲ)(Ir(ppy)3)合成水溶性铱纳米棒(IrNDs).在共反应试剂三丙胺(TPrA)存在下,IrNDs表现出优良的ECL性能.借助多巴胺(DA)对Ir NDs-TPrA体系EC...     

A Perylene Bisimide Cyclophane as a “Turn‐On” and “Turn‐Off” Fluorescence Probe

A rigid, covalently linked perylene‐3,4:9,10‐tetracarboxylic acid bisimide (PBI) cyclophane was synthesized by imidization of a bay‐substituted perylene bisanhydride with p‐xylylenediamine. The interchromophoric distance of approximately 6.5 Å establishes an ideal rigid cavity for the encapsulation of large aromatic compounds such as perylene and anthracene with binding constants up to 4.6×10⁴ M ^?1 (in CHCl₃). For electron‐poor guest molecules, the complexation process is accompanied by a significantly increased fluorescence, whereas the emission intensity is dramatically quenched by more electron‐rich guests because of the formation of charge‐transfer complexes. Furthermore, the influence of the PBI core twist on the binding constant results in a remarkable selectivity towards more flexible aromatic guest molecules.     

Knots “Choke Off” Polymers upon Stretching

Long polymer chains inevitably get tangled into knots. Like macroscopic ropes, polymer chains are substantially weakened by knots and the rupture point is always located at the “entry” or “exit” of the knot. However, these phenomena are only poorly understood at a molecular level. Here we show that when a knotted polyethylene chain is tightened, most of the stress energy is stored in torsions around the curved part of the chain. The torsions act as “work funnels” that effectively localize mechanical stress in the immediate vicinity of the knot. As a result, the knot “chokes” the chain at its entry or exit, thus leading to bond rupture at much lower forces than those needed to break a linear, unknotted chain. Our work not only explains the weakening of the polymer chain and the position of the rupture point, but more generally demonstrates that chemical bonds do not have to be extensively stretched to be broken.     

Supramolecular Silicone Elastomers with Healable and Hydrophobic Properties Crosslinked by “Salt‐Forming Vulcanization”

In this article, supramolecular silicone elastomers with self‐healing function were first prepared by simple and controllable “salt‐forming vulcanization” of polyaminopropylmethylsiloxane with acids. Their structures and micrographs were verified by Fourier transform infrared spectra, Small‐angle X‐ray scattering experiments and atomic force microscope. The experimental results showed that the ion‐association complexes were formed during vulcanization, and the obtained elastomers displayed self‐healing and good mechanical properties even if the cross‐linking agent was excessed. The thermogravimetric analysis showed that the elastomers crosslinked by inorganic acid were stable under high temperature. Unexpectedly, bionic structures were observed in the elastomers, which further changed the hydrophobicity of the surfaces of the elastomers physically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 903–911     

Gold Nanoparticle–Fluorophore Complexes: Sensitive and Discerning “Noses” for Biosystems Sensing

Gold nanoparticles (NPs) efficiently quench adsorbed fluorophores. Upon disruption of such complexes by an analyte, fluorescence turn‐on is observed. By judicious choice of the functionalized NP and the fluorophore, these complexes display different responses to analytes, thus leading to versatile yet simple array‐based sensor platforms. Using this strategy, we can identify proteins in buffer and serum, distinguish between both different species and different strains of bacteria, and differentiate between healthy, cancerous, and metastatic human and murine cells.     

An Allosteric Receptor by Simultaneous “Casting” and “Molding” in a Dynamic Combinatorial Library

Allosteric synthetic receptors are difficult to access by design. Herein we report a dynamic combinatorial strategy towards such systems based on the simultaneous use of two different templates. Through a process of simultaneous casting (the assembly of a library member around a template) and molding (the assembly of a library member inside the binding pocket of a template), a Russian‐doll‐like termolecular complex was obtained with remarkable selectivity. Analysis of the stepwise formation of the complex indicates that binding of the two partners by the central macrocycle exhibits significant positive cooperativity. Such allosteric systems represent hubs that may have considerable potential in systems chemistry.     

“Armor‐Plating” Enzymes with Metal–Organic Frameworks (MOFs)

Cell‐free enzymatic catalysis (CFEC) is an emerging biotechnology that enable the biological transformations in complex natural networks to be imitated. This biomimetic approach allows industrial products such as biofuels and biochemical to be manufactured in a green manner. Nevertheless, the main challenge in CFEC is the poor stability, which restricts the effectiveness and lifetime of enzymes in sophisticated applications. Immobilization of the enzymes within solid carriers is considered an efficient strategy for addressing these obstacles. Specifically, putting an “armor‐like” porous metal–organic framework (MOF) exoskeleton tightly around the enzymes not only shields the enzymes against external stimulus, but also allows the selective transport of guests through the accessible porous network. Herein we present the concept of this biotechnology of MOF‐entrapped enzymes and its cutting‐edge applications.     

Voltammetric Monitoring and Speciation of Copper Ions in Italian “Grappa” with Platinum Microelectrodes

A linear sweep voltammetric (LSV) investigation and the anodic stripping voltammetric (ASV) detection of copper ions in ethanol‐water mixtures and grappa samples are reported. The measurements are carried out by using platinum microdisk electrodes. Ethanol‐water mixtures with ethanol content in the range 40–100 vol%, commercially available and raw grappa samples having ethanol content in the above range are examined. From LSV measurements of copper (II) ions added to the samples, the formation of intermediate copper (I) soluble species, which are stabilized mainly by the naturally occurring organic compounds present in the real samples, is observed. The analysis of LSV and ASV current responses against added Cu²⁺ ions provides linear trends over the concentration range 5×10^?5?5×10^?3 M and 5×10^?7?5×10^?5 M, respectively. The sensitivity depends on the ethanol content in the mixture and, as expected, it is the higher the lower the viscosity of the medium. In particular, it varies from 1.54 to 3.53 nA mM^?1 and from 0.114 to 0.263 nA μM^?1 for LSV and ASV measurements, respectively, upon changing the ethanol content from 40 to 100 vol%. In the same range of ethanol content, detection limits obtained by ASV vary from 0.27 to 0.15 μM, respectively. Labile or total copper contents in the grappa samples are determined by ASV measurements performed in the untreated matrices or in the samples acidified with 0.1 M HClO₄, respectively. Finally, acidification of the samples with different amounts of HClO₄ allows also some speciation investigations to be performed.     

Toward Main Chain Metallo‐Terpyridyl Supramolecular Polymers: “The Metal Does the Trick”

Metallo‐supramolecular chemistry offers possibilities for the construction of stimuli‐responsive polymeric materials where the environment can have a large impact on the reversibility and strength of interactions between the individual components. The potential of manipulating the strength of the intermolecular non‐covalent bonds can result in impressive modifications of the metallo‐supramolecular structure and, subsequently, produces changes in the properties of the designed material. The present feature article provides an overview on recent developments in the field of metallo‐polymerization of chelating terpyridyl and analogues ligands. Synthetic strategies are described followed by a discussion regarding the characterization and the application of the reviewed metallo‐supramolecular structures, mainly based on terpyridines.

     

Electrochemiluminescence of Carbon-based Quantum Dots: Synthesis,Mechanism and Application in Heavy Metal Ions Detection

In recent years, carbon-based quantum dots as luminophores and co-reactants have aroused broad interest for their ability to function in electrochemiluminescence (ECL) sensors due to their unique features, including excellent biocompatibility, low toxicity, and water solubility. In this mini review, the synthesis methods of carbon-based quantum dots are firstly introduced. Then, the mechanism of carbon-based quantum dots as luminophores and co-reactants and their latest progress application in the detection of heavy metal ions are explored. Finally, the current challenges and potential future development directions of carbon-based quantum dots in ECL sensing filed for heavy metal ions analysis are summarized.