In situ Electrochemical Synthesis of a Composite Film Containing Nickel Hexacyanoferrate and Bentonite Clay for the Sensitive Determination of Acetaminophen and Dopamine

A composite film of nickel hexacyanoferrate (NiHCF) and bentonite (Bt) clay (abbreviated as NiHCF?Bt) is synthesized by an in situ electrochemical method. For this synthesis, nickel ions are immobilized on Bt clay by an ion‐exchange process, equilibrating Bt clay with nickel nitrate. On a glassy carbon electrode (GCE), the nickel ion‐exchanged Bt clay (Ni²⁺?Bt) is coated to get the modified electrode which is represented as GCE/Ni²⁺?Bt. The NiHCF?Bt composite film is prepared on the GCE surface using the GCE/Ni²⁺?Bt and scanning the electrode potentials between ?0.10 to 1.00 V continuously in an aqueous solution containing potassium hexacyanoferrate and potassium chloride. This NiHCF?Bt modified GCE (GCE/NiHCF?Bt) exhibits redox peaks due to the oxidation and reduction of the central metal ion, Fe²⁺. The electro‐generated Fe³⁺ present in the GCE/NiHCF?Bt, electrocatalytically oxidizes a range of drugs like acetaminophen (AC), dopamine (DA), and tyrosine (TY) at decreased overpotentials with high current. This property is advantageously used for the precise quantification of AC, DA, and TY. Sensitivity, limit of detection, and linear calibration range for the determination of AC are found to be 0.20 μA μM^?1 cm^?2, 1.5 μM, and 25.0–1000.0 μM, respectively. Further, the amount of AC present in pharmaceutical products is satisfactorily quantified which demonstrated the use of the NiHCF?Bt composite film in electroanalysis.     

An Activity‐Based Sensing Approach for the Detection of Cyclooxygenase‐2 in Live Cells

Cyclooxygenase‐2 (COX‐2) overexpression is prominent in inflammatory diseases, neurodegenerative disorders, and cancer. Directly monitoring COX‐2 activity within its native environment poses an exciting approach to account for and illuminate the effect of the local environments on protein activity. Herein, we report the development of CoxFluor, the first activity‐based sensing approach for monitoring COX‐2 within live cells with confocal microscopy and flow cytometry. CoxFluor strategically links a natural substrate with a dye precursor to engage both the cyclooxygenase and peroxidase activities of COX‐2. This catalyzes the release of resorufin and the natural product, as supported by molecular dynamics and ensemble docking. CoxFluor enabled the detection of oxygen‐dependent changes in COX‐2 activity that are independent of protein expression within live macrophage cells.     

Nickel‐Catalyzed Cross‐Coupling of Sulfonamides With (Hetero)aryl Chlorides

The development of Ni‐catalyzed C?N cross‐couplings of sulfonamides with (hetero)aryl chlorides is reported. These transformations, which were previously achievable only with Pd catalysis, are enabled by use of air‐stable ( L )NiCl(o‐tol) pre‐catalysts (L= PhPAd‐DalPhos and PAd2‐DalPhos ), without photocatalysis. The collective scope of (pseudo)halide electrophiles (X=Cl, Br, I, OTs, and OC(O)NEt₂) demonstrated herein is unprecedented for any reported catalyst system for sulfonamide C?N cross‐coupling (Pd, Cu, Ni, or other). Preliminary competition experiments and relevant coordination chemistry studies are also presented.     

Amidinato Germylene‐Zinc Complexes: Synthesis,Bonding, and Reactivity

Despite the explosive growth of germylene compounds as ligands in transition metal complexes, there is a modicum of precedence for the germylene zinc complexes. In this work, the synthesis and characterization of new germylene zinc complexes [PhC(NtBu)₂Ge{N(SiMe₃)₂}→ZnX₂]₂ (X= Br ( 2 ) and I ( 3 )) supported by (benz)‐amidinato germylene ligands are reported. The solid‐state structures of 2 and 3 have been validated by single‐crystal X‐ray diffraction studies, which revealed the dimeric nature of the complexes, with distorted tetrahedral geometries around the Ge and Zn center. DFT calculations reveal that the Ge–Zn bonds in 2 and 3 are dative in nature. The reaction of 2 with elemental sulfur resulted in the first structurally characterized germathione stabilized ZnBr₂ complexes PhC(NtBu)₂Ge(=S){N(SiMe₃)₂}→ZnBr₂ ( 5 ). Therefore, the Ge=S in 5 is in‐between Ge–S single and Ge=S double bond length, owing to the coordination of a sulfur lone pair of electrons to ZnBr₂.     

An Activity-Based Sensing Approach for the Detection of Cyclooxygenase-2 in Live Cells

Cyclooxygenase-2 (COX-2) overexpression is prominent in inflammatory diseases, neurodegenerative disorders, and cancer. Directly monitoring COX-2 activity within its native environment poses an exciting approach to account for and illuminate the effect of the local environments on protein activity. Herein, we report the development of CoxFluor, the first activity-based sensing approach for monitoring COX-2 within live cells with confocal microscopy and flow cytometry. CoxFluor strategically links a natural substrate with a dye precursor to engage both the cyclooxygenase and peroxidase activities of COX-2. This catalyzes the release of resorufin and the natural product, as supported by molecular dynamics and ensemble docking. CoxFluor enabled the detection of oxygen-dependent changes in COX-2 activity that are independent of protein expression within live macrophage cells.     

Interplay between two spin states determines the hydroxylation catalyzed by P450 monooxygenase from Trichoderma brevicompactum

Tri11 (now renamed as tri22) encoded cytochrome P₄₅₀ monooxygenase in Trichoderma brevicompactum catalyzes the C-4 C-H hydroxylation of 12, 13-epoxytrichothec-9-ene (EPT) to produce trichodermol in the biosynthetic pathway of trichodermin/harzianum A. The density functional theory (DFT)-quantum mechanics (QM) approach is applied to elucidate the hydroxylation of EPT by using a model active species of P₄₅₀ (Cpd I). The QM calculations were performed on the active site complex, to find out transition-state structure, intermediate, and product complexes for the two spin states at different potential energy surfaces. The two state reactivity rebound-free product formation resulted from the interplay of two spin states (doublet and quartet).     

Direct determination of uranium in sintered deeply depleted uranium oxide pellets by wavelength dispersive X-ray fluorescence spectrometry

This paper presents studies on direct non-destructive determination of uranium in sintered deeply depleted (DD) uranium oxide (UO₂) pellets by wavelength dispersive X-ray fluorescence (WDXRF) spectrometry. A special collet was designed and fabricated for holding the sintered DDUO₂ pellets for direct analysis, thus avoiding the sample preparation steps. The samples were analyzed using a calibration plot obtained from WDXRF spectra of matrix matched calibration standards. The WDXRF determined uranium values were found to be in very close agreement with titrimetric values and has reproducibility better than 0.05% (RSD, 1 s, n = 10) for the sintered DDUO₂ pellets having U: 86.81–88.04 wt%.

     

One-pot multicomponent synthesis and antimicrobial evaluation of novel tricyclic indenopyrimidine-2-amines

The synthesis of novel tricyclic indenopyrimidine-2-amines from 3,3-dimethyl-/3-methyl-2H-indanones has achieved by base-catalyzed one-pot three-component reaction. The desired products are formed within 10 hours after addition at reflux temperature. This multicomponent approach offers a viable protocol for the construction of indenopyrimidine-2-amines in single-step without the isolation of the intermediates 3,3-dimethyl/3-methyl-2-(4-substituted benzylidene)-2,3-dihydro-1H-inden-1-ones. All the synthesized compounds have been screened for antimicrobial activity and some of the derivatives show comparable activity against bacterial and fungal isolates.     

Microwave-assisted synthesis and biological evaluation of pyrazole-4-carbonitriles as antimicrobial agents

An efficient microwave-assisted method of synthesis of pyrazole-4-carbonitriles has been developed. Condensation of pyrazole-4-carbaldehydes with hydroxylamine hydrochloride followed by reaction of the resulting oximes with the Vilsmeier-Haack reagent pre-formed from phthaloyl dichloride and dimethylformamide under microwave irradiation afforded the corresponding pyrazole-4-carbonitriles in 73% to 91% yield. The operational simplicity, avoidance of toxic reagents such as POCl₃, shorter reaction time, higher yield compared to the classical version, easy work up, and the use of the by-product in the regeneration of phthaloyl dichloride are the advantages of this methodology. All the target compounds were tested for antimicrobial activity against Gram-positive bacteria Bacillus cereus and Staphylococcus aureus; Gram-negative bacteria Escherichia coli and Yersinia enterocolitica, and the fungal species Candida albicans.     

Experimental and theoretical investigation on adsorption and corrosion inhibition properties of imidazopyridine derivatives on mild steel in hydrochloric acid solution

Imidazopyridine derivatives, namely 4‐methoxy‐N‐((2‐(4‐methoxyphenyl)H‐imidazo[1,2‐a]pyridin‐3‐yl)methylene)benzenamine (MMPIPB) and 4‐chloro‐N‐((2‐(4‐methoxyphenyl)H‐imidazo[1,2‐a]pyridin‐3yl)methylene)benzenamine (CMPIPB), were investigated as inhibitors for mild steel corrosion in 15% HCl solution using the weight loss and electrochemical techniques. According to electrochemical impedance spectroscopy studies, MMPIPB and CMPIPB show corrosion inhibition efficiency of 84.8 and 77.2% at 10‐ppm concentration and 98.1 and 94.8% at 80‐ppm concentration, respectively at 303 K. The corrosion inhibition efficiency of both inhibitors increased with increasing inhibitor concentration and decreased with increasing temperature. The adsorption of both inhibitor molecules on the surface of mild steel obeys Langmuir adsorption isotherm. Polarization studies showed that both studied inhibitors were of mixed type in nature. Electrochemical impedance spectroscopy studies showed that for both inhibitors, the value of charge transfer resistance increased and double‐layer capacitance decreased on increasing the concentration of inhibitors. Scanning electron microscopy, energy‐dispersive X‐ray spectroscopy (EDX), and atomic force microscopy were performed for surface study. The density functional theory was employed for theoretical calculations. Copyright © 2014 John Wiley & Sons, Ltd.