A novel magnetically separable laccase-mediator catalyst system for the aerobic oxidation of alcohols and 2-substituted-2,3-dihydroquinazolin-4(1H)-ones under mild conditions

In this study, a magnetically reusable artificial metalloenzyme has been constructed by co-immobilization of palladium nanoparticles as a strong oxidizing catalyst and laccase as an oxygen-activating enzyme into the cavities of magnetic mesocellular foams silica (Pd-Laccase@MMCF). The combination of Pd-Laccase@MMCF and hydroquinone (HQ) act as electron-transfer mediator system and make stepwise electron transfer from substrate to molecular oxygen. This catalyst system was used for the aerobic (i) oxidation of alcohols to the corresponding carbonyl compounds and (ii) dehydrogenation of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in phosphate buffer (0.1 M, pH 4.5, 4 mL)/THF (4%, 1 mL) as solvent under mild conditions. The co-immobilization of both laccase and Pd onto high surface area mesoporous support, high catalytic activity and magnetically separable and reusable make the present catalyst system superior to other currently available electron-transfer mediator systems.     

Synthesis,characterization and in vitro DNA binding studies of a new copper(II) complex containing an antiviral drug,valganciclovir

A new complex, [Cu(valcyte)₂(NO₃)₂], in which valcyte served as a valganciclovir drug, was synthesized and characterized by different physicochemical methods. Optimization of ligand structures and their complexes with Cu²⁺ were performed by semi-empirical and DFT methods. Binding interaction of this complex with calf-thymus DNA (ct-DNA) was explored by emission, absorption, circular dichroism and viscosity techniques. Additionally, cell line targeting was studied and cytotoxic effects of [Cu(valcyte)₂(NO₃)₂] (0.0–160 μg) on AGS and MCF-7 cell lines were reported. Percentage of Cell Viability and Apoptotic Index were assessed. The complex displayed significant binding properties to ct-DNA. Undertaking fluorometric studies, the binding mode of the complex with ct-DNA was explored utilizing Hoechst as a fluorescence probe, indicating the binding to be of groove mode. The DNA viscosity altered slightly in presence of the complex. Enthalpy and entropy changes during the interaction showed that the process is endothermic, with the complex mainly bound to ct-DNA by hydrophobic attraction. Values of ΔG revealed a spontaneous reaction between DNA and the complex. Optimized docked model of DNA–complex mixture confirmed the experimental results. The results of MMFF94 calculations indicated stability of [Cu(valcyte)₂(NO₃)₂] after docking with the modeled DNA profile, as compared to the DNA profile and valganciclovir results before the docking process. Cytotoxicity studies showed that an increase in [Cu(valcyte)₂(NO₃)₂] may result in a significant decrease in cell viability and increase apoptosis index in the treated cells, as compared to valganciclovir treated cells (p < 0.05). The findings further showed that [Cu(valcyte)₂(NO₃)₂] has potential for use in cancer therapy.     

A combined theoretical and thermal analysis study on the solid state linkage isomerization of Ni(II)-nitrite complexes with ethylenediamine derivatives*

Solid state stepwise nitro–nitrito linkage isomerization of trans-[dinitrobis(ethylenediamine)nickel(II)], [Ni(en)₂(NO₂)₂] (N,N-en), trans-[dinitrobis(N,N′-dimethylethylenediamine)nickel(II)], [Ni(N,N′-dmen)₂(NO₂)₂] (N,N-dmen), and trans-[dinitritobis(N,N-dimethylethylenediamine)nickel(II)], [Ni(N,N-dmen)₂(ONO)₂] (O,O-udmen) were investigated by performing non-isothermal differential scanning calorimetry (DSC) analyses and the thermodynamic and thermokinetic parameters of isomerization were determined using DSC curves. Both N,N-en and N,N-dmen DSC curves show an endothermic peak at elevated temperatures, attributed to dinitro-to-dinitrito linkage isomerization. Similar exothermic peaks were observed in the cooling cycle, assigned to the reverse dinitrito-to-dinitro isomerization. The O,O-udmen isomer is more stable than the corresponding dinitro one at ambient temperatures, but an exothermic dinitrito-to-dinitro isomerization occurs upon cooling down to ?70 °C and reverts endothermically to dinitrito isomer upon heating up to ambient temperature. The overlapping DSC peaks associated with stepwise linkage isomerization were resolved using nonlinear fitting method. The peak temperature and the enthalpy changes of linkage isomerization are inversely dependent on the steric hindrance provided by diamine ligands, which increases in the order udmen > dmen > en. The results showed that the steric factor of the co-ligands also influences the kinetic parameters of isomerization, so that more bulky ligand substituent leads to higher isomerization rate constants. A DFT and TD-DFT calculations have been carrid out on both dinitro complexes of this investigation .     

Synthesis,Characterization, and DNA Binding Studies of a New Pt(II) Complex Containing the Drug Levetiracetam: Combining Experimental and Computational Methods

The water-soluble platinum(II) complex, [Pt(LV)(dmso)Cl]Cl (LV is Levetiracetam an anti-epileptic drug belonging to the pyrrolidine family) was synthesized and characterized using physico-chemical, spectroscopic and computational methods. Multi-spectroscopic methods used to study the interaction of Pt(II) complex with calf thymus (ct-DNA) in Tris–HCl buffer solution (pH 7.4). The Pt(II) complex was found to be a minor groove binder with a preference for the A-T region compared to the G-C region. This was substantiated by displacement studies with Hoechst 33258, a known minor groove binder. The mean binding constant obtained from the spectroscopic techniques was 7?×?10⁴ M^?1. In comparison with the previous study, the binding constant of Pt(II) complex is 15 times greater than the corresponding value of levetiracetam. These results indicate that the binding affinity of Pt(II) complex is stronger than levetiracetam.     

Electrochemical oxidation of 2,3-dimethylhydroquinone in the presence of 1,3-dicarbonyl compounds

The electrooxidation of 2,3-dimethylhydroquinone (1) has been studied in the presence of 2-phenyl-1,3-indandione (3a), 3-hydroxy-1H-phenalen-1-one (3b), and 2-chloro-5,5-dimethyl-1,3-cyclohexanedione (3c) as CH acid nucleophiles in water/acetonitrile (85/15) solution, using cyclic voltammetry and controlled-potential coulometry. The results indicate that p-benzoquinone, generated by electrochemically driven oxidation of the 2,3-dimethylhydroquinone (1), is scavenged by 3a-c, to give related products (5a, 9b, 8c) via various electrochemical mechanisms. The electrochemical syntheses of 5a, 9b, and 8c have been successfully performed in one-pot in an undivided cell using an environmentally friendly method with high atomic economy.     

Human serum albumin binding studies of a new platinum(IV) complex containing the drug pregabalin: experimental and computational methods

A new platinum(IV) complex, [Pt(en)(Cl)₂(Pregabalin)₂], containing the drug pregabalin was synthesized and characterized by elemental analysis, FT-IR, ¹H NMR, mass spectrum, thermogravimetric analysis (TGA), molecular docking and RHF/PM6 method. Also, the interaction of Pt(IV) complex with human serum albumin (HSA) was studied by using UV–vis, fluorometric, circular dichroism (CD) spectroscopies and molecular docking techniques. The results demonstrated that the binding of the complex to HSA caused strong fluorescence quenching of HSA through static quenching mechanism. Hydrogen bonds and van der Waals contacts are the major forces in the stability of protein-Pt(IV) complex and the process of the binding of complex with HSA was enthalpy driven (ΔH = –105.8?kJ·mol^?1). The results of CD and UV–vis spectroscopy indicated that the binding of the complex to HSA caused conformational changes in HSA. In addition, the study of molecular docking and RHF/PM6 method confirm the experimental results with respect to the mechanism of binding.     

Four-component synthesis of ferrocene-containing 1,3,4-oxadiazoles from N-isocyaniminotriphenylphosphorane (Ph3PNNC), a primary amine,a cyclic ketone and ferrocene carboxylic acid

The 1:1 imine intermediate created by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane (Ph₃PNNC) in the presence of ferrocene carboxylic acid and the corresponding iminophosphorane intermediate was formed. Afterwards, ferrocene containing 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reaction proceeded under mild conditions at room temperature.     

Antimicrobial activity of PVC-pyrazolone-silver nanocomposites

Poly(vinyl chloride)-pyrazolone; PVC-pz as a new modified form of PVC with high antibacterial and antifungal activities towards some Gram +ve bacteria S. Aureus, B. Subtilis and S. Faecalis) and Gram –ve bacteria (E. Coli, P. Aeruginosa and N. Gonorrhoeae) beside Candida albicans in addition to Aspragillus flavus as fungi has been synthesized in absence and in presence of silver-nanoparticles, AgNPs, in 3 and 5% by weight with respect to PVC. This was developed by a chemical reaction of PVC 1, and pyrazolone 2 in tetrahydrofuran, THF as solvent. PVC-pz derivative has been characterized by FTIR, ¹HNMR spectroscopic analyses, in addition to scanning and transmission electronic microscopy. Photostability of PVC-pz was evaluated by following the discoloration for UV- irradiated samples colorimetrically in accordance with degradation time. IR and ¹H-NMR analyses confirm that PVC-pz, 4 was formed indicating a substitution reaction of chlorine atoms of PVC chains to the hydrogen atom of active methylene and that attached to pyrazolone nitrogen at the same time. Antimicrobial activities of PVC-pz increased in the presence of AgNPs and with increasing its percentage.     

Cooling-Assisted Headspace Hollow Fiber-Based Liquid-Phase Microextraction Setup for Direct Determination of PAHs in Solid Samples by Using Volatile Solvents

To reinforce the extraction efficiency of the liquid- and solid-phase microextraction methods, different cooling-assisted setups have been employed, most of which are complicated, expensive, tedious, and do not show good performances due to indirect transfer of cold to the extraction phase. In this research, a simple, low-cost and effective cooling-assisted headspace hollow fiber-based liquid-phase microextraction (CA-HS-HF-LPME) device was fabricated and evaluated, which is able to directly cool down the extraction phase in different modes of LPME. It was coupled to GC-FID and utilized for the direct determination of PAHs in contaminated soil samples using volatile organic solvents. Different effective experimental variables including type and volume of extraction solvent, extraction time and temperature, and temperature of the cooled organic solvent were evaluated and optimized. Under the optimized experimental conditions (e.g., organic extracting solvent: 3 µL of acetone; extraction time: 20 min; extraction temperature: 90 °C; and temperature of cooled organic drop: −25 °C), good linearity of calibration curves (R ² > 0.99) was obtained in a concentration range of 1–10,000 ng g⁻¹. The limits of detection (LODs) were obtained over the range of 0.01–0.1 ng g⁻¹. The relative standard deviations (RSD%, n = 6) of 0.1 µg g⁻¹ PAHs were found to be 4.7–10.1 %. The CA-HS-HF-LPME-GC-FID method was successfully used for the direct determination of PAHs in contaminated soil and plant samples, with no sample manipulation. The results were in agreement with those obtained by a validated ultrasound-assisted solvent extraction (UA-SE) method.