Single-molecule detection is the ultimate sensitivity in analytical chemistry and has been largely unavailable in electrochemical analysis. Here, we demonstrate the feasibility of detecting ...electrochemically inactive single biomacromolecules, such as enzymes, antibodies, and DNA, by blocking a solution redox reaction when molecules adsorb and block electrode sites. By oxidizing a large concentration of potassium ferrocyanide on an ultramicroelectrode (UME, radius ≤150 nm), time-resolved, discrete adsorption events of antibodies, enzymes, DNA, and polystyrene nanospheres can be differentiated from the background by their “footprint”. Further, by assuming that the mass transport of proteins to the electrode surface is controlled mainly by diffusion, a size estimate using the Stokes–Einstein relationship shows good agreement of electrochemical data with known protein sizes.
Adhesive hydrogels have gained popularity in biomedical applications, however, traditional adhesive hydrogels often exhibit short-term adhesiveness, poor mechanical properties and lack of ...antibacterial ability. Here, a plant-inspired adhesive hydrogel has been developed based on Ag-Lignin nanoparticles (NPs)triggered dynamic redox catechol chemistry. Ag-Lignin NPs construct the dynamic catechol redox system, which creates long-lasting reductive-oxidative environment inner hydrogel networks. This redox system, generating catechol groups continuously, endows the hydrogel with long-term and repeatable adhesiveness. Furthermore, Ag-Lignin NPs generate free radicals and trigger self-gelation of the hydrogel under ambient environment. This hydrogel presents high toughness for the existence of covalent and non-covalent interaction in the hydrogel networks. The hydrogel also possesses good cell affinity and high antibacterial activity due to the catechol groups and bactericidal ability of Ag-Lignin NPs. This study proposes a strategy to design tough and adhesive hydrogels based on dynamic plant catechol chemistry.
The fourth edition of this highly-successful, concise text contains twenty percent new data. Also included now are chapters on (19)F-NMR and (31)P-NMR as well as references to important Raman bands. ...Contains nearly 500 illustrations.
Self-powered artificial nanomotors are currently attracting increased interest as mimics of biological motors but also as potential components of nanomachinery, robotics, and sensing devices. We have ...recently described the controlled shape transformation of polymersomes into bowl-shaped stomatocytes and the assembly of platinum-driven nanomotors. However, the platinum encapsulation inside the structures was low; only 50% of the structures contained the catalyst and required both high fuel concentrations for the propelling of the nanomotors and harsh conditions for the shape transformation. Application of the nanomotors in a biological setting requires the nanomotors to be efficiently propelled by a naturally available energy source and at biological relevant concentrations. Here we report a strategy for enzyme entrapment and nanomotor assembly via controlled and reversible folding of polymersomes into stomatocytes under mild conditions, allowing the encapsulation of the proteins inside the stomach with almost 100% efficiency and retention of activity. The resulting enzyme-driven nanomotors are capable of propelling these structures at low fuel concentrations (hydrogen peroxide or glucose) via a one-enzyme or two-enzyme system. The confinement of the enzymes inside the stomach does not hinder their activity and in fact facilitates the transfer of the substrates, while protecting them from the deactivating influences of the media. This is particularly important for future applications of nanomotors in biological settings especially for systems where fast autonomous movement occurs at physiological concentrations of fuel.
In this study, the antioxidant and antiradical properties of some phyto lignans (nordihydroguaiaretic acid, secoisolariciresinol, secoisolariciresinol diglycoside, and α-(-)-conidendrin) and ...mammalian lignans (enterodiol and enterolactone) were examined by different antioxidant assays. For this purpose, radical scavenging activities of phyto and mammalian lignans were realized by 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical (ABTS
) scavenging assay and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging assay. Additionally, the reducing ability of phyto and mammalian lignans were evaluated by cupric ions (Cu
) reducing (CUPRAC) ability, and ferric ions (Fe
) and Fe
-(TPTZ)2
complex reducing (FRAP) abilities. Also, half maximal inhibitory concentration (IC
) values were determined and reported for DPPH
and ABTS
scavenging influences of all of the lignan molecules. The absorbances of the lignans were found in the range of 0.150-2.320 for Fe
reducing, in the range of 0.040-2.090 for Cu
reducing, and in the range of 0.360-1.810 for the FRAP assay. On the other hand, the IC
values of phyto and mammalian lignans were determined in the ranges of 6.601-932.167 µg/mL for DPPH
scavenging and 13.007-27.829 µg/mL for ABTS
scavenging. In all of the used bioanalytical methods, phyto lignans, as secondary metabolites in plants, demonstrated considerably higher antioxidant activity compared to that of mammalian lignans. In addition, it was observed that enterodiol and enterolactone exhibited relatively weaker antioxidant activities when compared to phyto lignans or standard antioxidants, including butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), Trolox, and α-tocopherol.
Selective oxidation to synthesize nitriles is critical for feedstock manufacturing in the chemical industry. Current strategies typically involve substitutions of alkyl halides with toxic cyanides or ...the use of strong oxidation reagents (oxygen or peroxide) under ammoxidation/oxidation conditions, setting considerable challenges in energy efficiency, sustainability, and production safety. Herein, we demonstrate a facile, green, and safe electrocatalytic route for selective oxidation of amines to nitriles under ambient conditions, assisted by the anodic water oxidation on metal-doped α-Ni(OH)2 (a typical oxygen evolution reaction catalyst). By controlling the balance between co-adsorption of the amine molecule and hydroxyls on the catalyst surface, we demonstrate that Mn doping significantly promotes the subsequent chemical oxidation of amines, resulting in Faradaic efficiencies of 96% for nitriles under ≥99% conversion. This anodic oxidation is further coupled with cathodic hydrogen evolution for overall atomic economy and additional green energy production.
Most general anaesthetics and classical benzodiazepine drugs act through positive modulation of γ-aminobutyric acid type A (GABA
) receptors to dampen neuronal activity in the brain
. However, direct ...structural information on the mechanisms of general anaesthetics at their physiological receptor sites is lacking. Here we present cryo-electron microscopy structures of GABA
receptors bound to intravenous anaesthetics, benzodiazepines and inhibitory modulators. These structures were solved in a lipidic environment and are complemented by electrophysiology and molecular dynamics simulations. Structures of GABA
receptors in complex with the anaesthetics phenobarbital, etomidate and propofol reveal both distinct and common transmembrane binding sites, which are shared in part by the benzodiazepine drug diazepam. Structures in which GABA
receptors are bound by benzodiazepine-site ligands identify an additional membrane binding site for diazepam and suggest an allosteric mechanism for anaesthetic reversal by flumazenil. This study provides a foundation for understanding how pharmacologically diverse and clinically essential drugs act through overlapping and distinct mechanisms to potentiate inhibitory signalling in the brain.
The ambiphilic triphosphine−borane ligand 1 {TPB = o-iPr2P-(C6H4)3B} readily coordinates to all group 10 and 11 metals to afford a complete series of metal boratranes (TPB)M 2−8 (2: M = Ni, 3: M = ...Pd, 4: M = Pt, 5: M = CuCl, 6: M = AgCl, 7: M = AuCl, 8: M = Au+). Spectroscopic and structural characterization unambiguously establishes the presence of M→B interactions in all of these complexes. The first evidence for borane coordination to copper and silver is provided, and the Au→B interaction is shown to persist upon chloride abstraction. Experimental and theoretical considerations indicate that the M→B interaction is strongest in the Pt and Au complexes. The influence of the oxidation state and charge of the metal is substantiated, and the consequences of relativistic effects are discussed. The coordination of the σ-acceptor borane ligand is found to induce a significant bathochromic shift of the UV−vis spectra, the Ni, Pd, and Pt complex presenting strong absorptions in the visible range. In addition, all of the group 10 and 11 metal boratranes adopt C 3 symmetry both in the solid state and in solution. The central M→B interaction is found to moderately influence the degree of helicity and configurational stability of these three-bladed propellers, and DFT calculations support a dissociative pathway for the inversion process.
Pd-catalyzed cross-coupling reactions that form C–N bonds have become useful methods to synthesize anilines and aniline derivatives, an important class of compounds throughout chemical research. A ...key factor in the widespread adoption of these methods has been the continued development of reliable and versatile catalysts that function under operationally simple, user-friendly conditions. This review provides an overview of Pd-catalyzed N-arylation reactions found in both basic and applied chemical research from 2008 to the present. Selected examples of C–N cross-coupling reactions between nine classes of nitrogen-based coupling partners and (pseudo)aryl halides are described for the synthesis of heterocycles, medicinally relevant compounds, natural products, organic materials, and catalysts.
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