Electropolymerized Diphenylamine on Functionalized Multiwalled Carbon Nanotube Composite Film and Its Application to Develop a Multifunctional Biosensor

Diphenylamine (DPA) monomers have been electropolymerized on the amino‐functionalized multiwalled carbon nanotube (AFCNT) composite film modified glassy carbon electrode (GCE) by cyclic voltammetry (CV). The surface morphology of PDPA‐AFCNT was studied using field‐emission scanning electron microscopy (FE‐SEM). The interfacial electron transfer phenomenon at the modified electrode was studied using electrochemical impedance spectroscopy (EIS). The PDPA‐AFCNT/GCE represented a multifunctional sensor and showed good electrocatalytic behavior towards the oxidation of catechol and the reduction of hydrogen peroxide. Rotating‐disk electrode technique was applied to detect catechol with a sensitivity of 1360 µA mM^?1 cm^?2 and a detection limit of 0.01 mM. Amperometric determination of hydrogen peroxide at the PDPA‐AFCNT film modified electrode results in a linear range from 10 to 800 µM, a sensitivity of 487.1 µA mM^?1 cm^?2 and detection limit of 1 µM. These results show that the nano‐composite film modified electrode can be utilized to develop a multifunctional sensor.     

Reversing current rectification to improve DNA‐sensing sensitivity in conical nanopores

Herein, we report the ultrasensitive DNA detection through designing an elegant nanopore biosensor as the first case to realize the reversal of current rectification direction for sensing. Attributed to the unique asymmetric structure, the glass conical nanopore exhibits the sensitive response to the surface charge, which can be facilely monitored by ion current rectification curves. In our design, an enzymatic cleavage reaction was employed to alter the surface charge of the nanopore for DNA sensing. The measured ion current rectification was strongly responsive to DNA concentrations, even reaching to the reversed status from the negative ratio (?6.5) to the positive ratio (+16.1). The detectable concentration for DNA was as low as 0.1 fM. This is an ultrasensitive and label‐free DNA sensing approach, based on the rectification direction‐reversed amplification in a single glass conical nanopore.     

Crystal structure,shape analysis and bioactivity of new LiI,NaI and MgII complexes with 1,10‐phenanthroline and 2‐(3,4‐dichlorophenyl)acetic acid

Reactions of 1,10‐phenanthroline (phen) and 2‐(3,4‐dichlorophenyl)acetic acid (dcaH) with M_n(CO₃) (M = Li^I, Na^I and Mg^II; n = 1 and 2) in MeOH yield the mononuclear lithium complex aqua[2‐(3,4‐dichlorophenyl)acetato‐κO](1,10‐phenanthroline‐κ²N,N′)lithium(I), [Li(C₈H₅Cl₂O₂)(C₁₂H₈N₂)(H₂O)] or [Li(dca)(phen)(H₂O)] ( 1 ), the dinuclear sodium complex di‐μ‐aqua‐bis{[2‐(3,4‐dichlorophenyl)acetato‐κO](1,10‐phenanthroline‐κ²N,N′)sodium(I)}, [Na₂(C₈H₅Cl₂O₂)₂(C₁₂H₈N₂)₂(H₂O)₂] or [Na₂(dca)₂(phen)₂(H₂O)₂] ( 2 ), and the one‐dimensional chain magnesium complex catena‐poly[[[diaqua(1,10‐phenanthroline‐κ²N,N′)magnesium]‐μ‐2‐(3,4‐dichlorophenyl)acetato‐κ²O:O′] 2‐(3,4‐dichlorophenyl)acetate monohydrate], {[Mg(C₈H₅Cl₂O₂)(C₁₂H₈N₂)(H₂O)₂](C₈H₅Cl₂O₂)·H₂O}_n or {[Mg(dca)(phen)(H₂O)₂](dca)·H₂O}_n ( 3 ). In these complexes, phen binds via an N,N′‐chelate pocket, while the deprotonated dca^? ligands coordinate either in a monodentate (in 1 and 2 ) or bidentate (in 3 ) fashion. The remaining coordination sites around the metal ions are occupied by water molecules in all three complexes. Complex 1 crystallizes in the triclinic space group P with one molecule in the asymmetric unit. The Li⁺ ion adopts a four‐coordinated distorted seesaw geometry comprising an [N₂O₂] donor set. Complex 2 crystallizes in the triclinic space group P with half a molecule in the asymmetric unit, in which the Na⁺ ion adopts a five‐coordinated distorted spherical square‐pyramidal geometry, with an [N₂O₃] donor set. Complex 3 crystallizes in the orthorhombic space group P2₁2₁2₁, with one Mg²⁺ ion, one phen ligand, two dca^? ligands and three water molecules in the asymmetric unit. Both dcaH ligands are deprotonated, however, one dca^? anion is not coordinated, whereas the second dca^? anion coordinates in a bidentate fashion bridging two Mg²⁺ ions, resulting in a one‐dimensional chain structure for 3 . The Mg²⁺ ion adopts a distorted octahedral geometry, with an [N₂O₄] donor set. Complexes 1 – 3 were evaluated against urease and α‐glucosidase enzymes for their inhibition potential and were found to be inactive.     

Pistagremic acid,a novel β-secretase enzyme (BACE1) inhibitor from Pistacia integerrima Stewart

A new triterpenic compound named pistagremic acid (PA) was once again isolated from Pistaciaintegerrima. The β-secretase inhibition study was carried out. Compound PA was found significantly active against β-secretase enzyme (BACE1) with IC₅₀ value of 350 ± 2 nM in comparison to the standard inhibitors [Asn670, Sta671, Val672]-amyloid-β/A4 precursor protein 770 fragment 662–675 (IC₅₀ = 290.71 ± 1 nM). The selectivity of this compound was also evaluated against the acetylcholinesterase and butyrylcholinesterase enzymes. Interestingly compound PA was found to be inactive against them and showed selectivity towards β-secretase enzyme (BACE1).     

Palladium‐Catalyzed Enantioselective Decarboxylative Cycloaddition of Vinylethylene Carbonates with Isocyanates

An efficient method for the enantioselective construction of β‐substituted β‐vinylglycinol derivatives through palladium‐catalyzed decarboxylative cycloaddition of vinylethylene carbonates with isocyanates was developed. By using a palladium complex generated in situ from [Pd₂(dba)₃] ? CHCl₃ (dba=dibenzylideneacetone) and (S)‐Segphos as a catalyst under mild reaction conditions, the process provided 4‐substituted‐4‐vinyloxazolidin‐2‐ones in high yields with a high level of enantioselectivity. The stereochemical outcome of the reaction was explained by DFT calculations and the synthetic utility of the process was demonstrated by the gram‐scale transformation and formal synthesis of MK‐0731 as a kinesin spindle protein inhibitor.     

Colorimetric determination ofm-aminophenol

Summary Potassium iodate reacts withm-aminophenol in presence of sulfuric acid to give pink violet color having 5g as visual limit of identification. The color reaction is specific form-aminophenol;o-, andp-aminophenol do not interfere if their amount does not exceed 10 and 70% respectively. This provides a new colorimetric method for the determination ofm-aminophenol in small quantities.

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Zusammenfassung Kaliumjodat reagiert mit m-Aminophenol in Gegenwart von Schwefelsäure unter Bildung einer rosavioletten Farbe mit einer Erfassungsgrenze von 5g. Die Reaktion ist spezifisch; o- und p-Aminophenol stören nicht, sofern nicht mehr als 10 bzw. 70% anwesend sind. Daraus ergibt sich ein neues kolorimetrisches Verfahren zur Bestimmung kleiner Mengen m-Aminophenol.

     

Spectrophotometric determination ofm-phenylenediamine

Summary A mixture of chloranil and cupric chloride-triphenylphosphine complex in acetone gives pinkish red color withm-phenylenediamine which provides the basis of a new spectrophotometric method for the determination ofm-phenylenediamine in minute quantities,o- andp-phenylene-diamines do not interfere with the determination if their amount does not exceed 90 and 7% respectively.

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Zusammenfassung Eine Mischung von Chloranil und Kupfer(II)-chlorid-triphenylphosphin in Aceton gibt mit m-Phenylendiamin(I) eine rosa Färbung, die zur Bestimmung kleiner Mengen von I geeignet ist. o- und p-Phenylendiamin stören nicht, sofern deren Menge 90 bzw. 7% nicht überschreitet.

     

Reactions with the Arylhydrazones of α-Cyanoketones: The Structure of 2-Arylhydrazono-3-ketimino-nitriles

Analysis of the IR., UV., and polarographic data of a variety of 2-arylhydrazono-3-ketimino-nitriles indicated that these derivatives exist mainly in the intramolecularly chelated hydrazone structure 1 . Compounds 1 reacted with hydrazine hydrate to yield the corresponding 5-amino-4-arylazopyrazoles ( 3 ). Compounds 3a reacted with acetylacetone, ethyl acetoacetate, and diethyl malonate to yield the pyrazolo[1, 5-a]pyrimidine derivatives 4, 5 , and 7 respectively. Compound 3a also reacted with benzoylisothiocyanate to yield the pyrazolyl thiourea derivative 8 .     

Spectrophotometric determination of nitrogen in small quantities of biological materials

Summary A new spot test for ammonium, by its reaction with ruthenium trichloride-triphenylphosphine, having a Ig limit of identification is reported. On the basis of this spot reaction a spectrophotometric method is described for the determination of minute quantities of NH₄-N from biological materials.

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Zusammenfassung Eine neue Tüpfelreaktion auf Ammonium wurde beschrieben, die auf der Umsetzung mit Rutheniumtrichlorid-Triphenylphosphin beruht. Die Erfassungsgrenze beträgt 1g. Mit Hilfe dieser Reaktion lassen sich kleinste Mengen Ammoniumstickstoff spektrophotometrisch in biologischem Material bestimmen.