Misfolding of Luciferase at the Single‐Molecule Level

The folding of complex proteins can be dramatically affected by misfolding transitions. Directly observing misfolding and distinguishing it from aggregation is challenging. Experiments with optical tweezers revealed transitions between the folded states of a single protein in the absence of mechanical tension. Nonfolded chains of the multidomain protein luciferase folded within seconds to different partially folded states, one of which was stable over several minutes and was more resistant to forced unfolding than other partially folded states. Luciferase monomers can thus adopt a stable misfolded state and can do so without interacting with aggregation partners. This result supports the notion that luciferase misfolding is the cause of the low refolding yields and aggregation observed with this protein. This approach could be used to study misfolding transitions in other large proteins, as well as the factors that affect misfolding.     

Recent Developments in the Plant‐Mediated Green Synthesis of Ag‐Based Nanoparticles for Environmental and Catalytic Applications

Among different metallic nanoparticles, sliver nanoparticles (Ag NPs) are one of the most essential and fascinating nanomaterials. Importantly, among the metal based nanoparticles, Ag NPs play a key role in various fields such as biomedicine, biosensors, catalysis, pharmaceuticals, nanoscience and nanotechnology, particularly in nanomedicine. A main concern about the chemical synthesis of Ag NPs is the production of hazardous chemicals and toxic wastes. To overcome this problem, many research studies have been carried out on the green synthesis of Ag NPs using green sources such as plant extracts, microorganisms and some biopolymers without formation of hazardous wastes. Among green sources, plants could be remarkably valuable to exploring the biosynthesis of Ag NPs. In this review, the green synthesis of Ag‐based nanocatalysts such as Ag NPs, AgPd NPs, Au?Ag NPs, Ag/AgPd NPs, Ag/Cu NPs, Ag@AgCl NPs, Au?Ag@AgCl nanocomposite, Ag?Cr‐AC nanocomposite and Ag NPs immobilized on various supports such as Natrolite zeolite, bone, ZnO, seashell, hazelnut shell, almond shell, SnO₂, perlite, ZrO₂, TiO₂, α‐Al₂O₃, CeO₂, reduced graphene oxide (rGO), h‐Fe₂O₃@SiO₂, and Fe₃O₄ using numerous plant extracts as reducing and stabilizing agents in the absence of hazardous surfactant and capping agents has been focused. This work describes the state of the art and future challenges in the biosynthesis of Ag‐based nanocatalysts. The fact about the application of living plants in metal nanoparticle (MNPs) industry is that it is a more economical and efficient biosynthesis biosynthetic procedure. In addition, the catalytic activities of the synthesized, Ag‐based recyclable nanocatalysts using various plant extracts in several chemical reactions such as oxidation, reduction, coupling, cycloaddition, cyanation, epoxidation, hydration, degradation and hydrogenation reactions have bben extensively discussed.     

Effect of single-wall carbon nanotubes on the properties of polymeric gel electrolyte dye-sensitized solar cells

A hybrid of polymer/dispersed single-wall carbon nanotubes was utilized in networking a novel composition of gel electrolyte in dye-sensitized solar cells. The gel is composed of polyethylene glycol, polyvinyl pyrrolidone, single-wall carbon nanotubes, and I^?/I₃ ^? as electrolyte. Formation of the less conductive polyiodide species in electrolyte was prohibited by the addition of single-wall carbon nanotubes leading to the excellent photovoltaic behavior of the cell under simulated standard illumination of the fabricated device owing to the increased open circuit voltage (0.47 V). Electrochemical impedance spectroscopy was employed to quantify the charge transport resistance and the electron lifetime at the TiO₂ conduction band. Charge transport resistances at the TiO₂/dye/electrolyte interface were determined for the cells consisting of the non-gel reference and our new gel electrolytes, and it was indicated that the charge recombination between injected electrons and electron acceptors (I₃ ^?) in the redox electrolyte was remarkably retarded. Electrochemical parameters obtained by the fitting showed all of the resistances increased as compared to liquid electrolyte dye-sensitized solar cells that can be related to the increase in viscosity of the gel, which hinders the ionic transportation through the electrolyte. These results were also confirmed by the electron lifetime analyses. The characteristic peak shifted to a lower frequency in the Bode phase plot for the cell containing gel electrolyte which is an indication of a longer electron lifetime in comparison with that of the cell containing very conventional liquid electrolyte.     

Hierarchical Organization of Ferrocene–Peptides

Hierarchical self‐assembly of disubstituted ferrocene (Fc)–peptide conjugates that possess Gly‐Val‐Phe and Gly‐Val‐Phe‐Phe peptide substituents leads to the formation of nano‐ and micro‐sized assemblies. Hydrogen‐bonding and hydrophobic interactions provide directionality to the assembly patterns. The self‐assembling behavior of these compounds was studied in solution by using ¹H NMR and circular dichroism (CD) spectroscopies. In the solid state, attenuated total reflectance (ATR) FTIR spectroscopy, single‐crystal X‐ray diffraction (XRD), powder X‐ray diffraction (PXRD), and scanning electron microscopy (SEM) methods were used. Spontaneous self‐assembly of Fc–peptides through intra‐ and intermolecular hydrogen‐bonding interactions induces supramolecular assemblies, which further associate and give rise to fibers, large fibrous crystals, and twisted ropes. In the case of Fc[CO‐Gly‐Val‐Phe‐OMe]₂ ( 1 ), molecules initially interact to form pleated sheets that undergo association into long fibers that form bundles and rectangular crystalline cuboids. Molecular offsets and defects, such as screw dislocations and solvent effects that occur during crystal growth, induce the formation of helical arrangements, ultimately leading to large twisted ropes. By contrast, the Fc–tetrapeptide conjugate Fc[CO‐Gly‐Val‐Phe‐Phe‐OMe]₂ ( 2 ) forms a network of nanofibers at the supramolecular level, presumably due to the additional hydrogen‐bonding and hydrophobic interactions that stem from the additional Phe residues.     

Multi-wall carbon nanotubes and TiO2 as a sensor for electrocatalytic determination of epinephrinein the presence of p-chloranil as a mediator

In this work, we describe an electrochemical method using p-chloranil as a mediator and multi-wall carbon nanotube and TiO₂ as sensors for sensitive determination of epinephrine (EP) in aqueous solution at pH = 10.0. It has been found that under optimum condition (pH 10.0) in cyclic voltammetry, the oxidation of EP occurred at a potential about 171 mV less positive than that unmodified carbon nanotube paste electrode. The diffusion coefficient (D) and the kinetic parameters, such as electron transfer coefficient, (α) and heterogeneous rate constant (k _h) for EP were also determined using electrochemical approaches. The electrocatalytic currents increase linearly with the EP concentration over the range 0.6–135 μM. The detection limits for EP will be equal to 0.25 μM. The relative standard deviation percentage values for 10.0 and 15.0 μM EP were 1.7% and 1.9%, respectively. Finally, this modified electrode was also examined as a selective, simple, and precise new electrochemical sensor for the determination of EP in real sample such as urine and epinephrine injection solution.     

Osmotic coefficient data and an excess Gibbs energy function for single-phase complex system of glucose + alcohol + water

Thermodynamics of single-phase complex systems of glucose + alcohol + water is significantly important in food and pharmaceutical industries. The water activity is a practical parameter in thermodynamic characterization in food and pharmaceutical and other biological industries, which its value has an important role in growing microorganisms and rate of reactions. In this work, the NRTL-NRF excess Gibbs function has extended for ternary system of water, different alcohols (as second molecular solvent) and a special molecular solute like a sugar. The extended NRTL-NRF model with three parameters was used for correlation of the osmotic coefficient of the aqueous systems of glucose and alcohol at different concentrations. The data of the osmotic coefficient of water for these systems are obtained by an isopiestic method. The adjustable parameters are calculated by optimization of the experimental data of the osmotic coefficient using the Nedler–Mead algorithm. It is shown that the results of the modified NRTL-NRF model demonstrate low deviation from the experimental data.     

Sono-catalytic degradation and fast mineralization of p-chlorophenol: La0.7Sr0.3MnO3 as a nano-magnetic green catalyst

La_0.7Sr_0.3MnO₃ (LSMO) nanoparticles with a perovskite structure were prepared by a combination of ultrasound and co-precipitation method. The synthesized catalyst was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy. The catalytic performance of the catalyst was evaluated for the degradation of 4-chlorophenol in the presence and in the absence of ultrasound. The degradation has been studied at different temperatures, pH, catalyst dosage, and initial concentration of 4-chlorophenol. The results have shown that the degradation efficiency was higher in the presence of ultrasound than its absence under the mild conditions. More than 88% decrease in the concentration and 85% decrease in the TOC for 4-chlorophenol could be achieved in a short time of sonication with respect to the conventional method. This behavior could be attributed to the cavitation process which followed by a high mass transfer on the catalyst with high surface area. These conditions led to facilitate the removal of pollutant from aqueous solution. The results also indicated that the catalyst without recalcination can be used successfully up to five consecutive cycles without any significant loss in activity in the presence and in the absence of ultrasound. In addition, the most important is the magnetic property of the nanoparticles which separated easily from aqueous solution by an external magnetic field.     

A survey on the effect of ionic liquid on electrochemical behavior and electrocatalytic activity of a phosphomolybdic acid-ionic liquid-MWCNT–modified glassy carbon electrode

Journal of Solid State Electrochemistry - The surface of a glassy carbon electrode modified with multi-walled carbon nanotubes (GCE/MWCNTs) was coated with a layer of phosphomolybdic acid (PMo12)...     

Ultrasounds-Assisted Electrosynthesis of Sponge-Like MnO2 Nanostructures: Design a Novel Device for Nanomolar Sensing of Dopamine

Russian Journal of Electrochemistry - In this paper we report direct electrochemical synthesis of sponge-like MnO2 nanostructures using ultrasonic vibration on the surface of MWCNT modified pencil...     

Heterogenized magnetic graphene oxide-supported N6-Schiff base Cu (II) complex as an exclusive nanocatalyst for synthesis of new pyrido[2,3-d]pyrimidine-7-carbonitrile derivatives

In this article, the synthesis of a novel and highly efficient recyclable and reusable heterogeneous nanocatalyst has been reported via the functionalizing of the Fe₃O₄-magnetized graphene oxide nanosheets with the N₆-Schiff base Cu (II) complex (GO/Fe₃O₄@SPNC). The structure of this novel nanocatalyst was determined by different analytical techniques such as FTIR, FE-SEM, TEM, TGA-DTG, and VSM. The catalytic activity of the synthesized GO/Fe₃O₄@SPNC nanocatalyst was explored for the synthesis of several new 2H-pyrido[3′,2′:6,7]pyrano[2,3-d]pyrimidine-7-carbonitrile derivatives with excellent yields. All new derivatives were fully identified by various spectral (¹H NMR, ¹³C NMR, FT-IR, ESI-MS) analyses. In addition, this nanocatalyst carried out satisfactory catalytic maintenance of activity and high chemical stability in the titled reactions after seven-time of recycling without substantial loss of leaching.