Determination of l-histidine by modified carbon paste electrode using tetra-3,4-pyridinoporphirazinatocopper(II)

This paper describes a potentiometric method for determination of l-histidine (l-his) in aqueous media, using a carbon paste electrode modified with tetra-3,4-pyridinoporphirazinatocopper(II) (Cu (3,4tppa)). The electrode exhibits linear response to the logarithm of the concentration of l-histidine from 2.4 × 10⁻⁵ to 1.0 × 10⁻² M, with a response slope of −49.5 ± 1 mV and response time of about 1.5 min. The detection limit according to IUPAC recommendation was 2.0 × 10⁻⁵ M. The proposed electrode shows a good selectivity for l-his over a wide variety of anions. This chemically modified carbon paste electrode was successfully used for the determination of l-his in a synthetic serum and RANDOX control serum solutions.     

Novel ionic liquid N,N-diethyl-N-sulfoethanaminium hydrogen sulfate: Design,characterization, and application as a highly efficient catalyst for the production of triazolo[1,2-a]indazole-triones and 2H-indazolo[2,1-b]phthalazine-triones

A novel Brønsted acidic ionic liquid namely N,N-diethyl-N-sulfoethanamminium hydrogen sulfate ([Et₃N-SO₃H]HSO₄) was synthesized, and characterized using FT-IR, ¹H NMR, ¹³C NMR, and mass data. Then, its catalytic activity was examined for the preparation of triazolo[1,2-a]-indazole-triones and 2H-indazolo[2,1-b]phthalazine-triones by the one-pot multi-component condensation of arylaldehydes with dimedone and 4-phenylurazole/2,3-dihydrophthalazine-1,4-dione under solvent-free conditions. [Et₃N-SO₃H]HSO₄ efficiently promoted the reaction to afford the products in high yields and in short reaction times.     

Fabrication and characterization of chitosan-gelatin/single-walled carbon nanotubes electrospun composite scaffolds for cartilage tissue engineering applications

Cartilage is a connective tissue with a slow healing rate due to lack in blood circulation and slow metabolism. Designing tissue engineering scaffolds modified based on its specific features can assist its natural regeneration process. In this study, the chitosan-gelatin/single-walled carbon nanotubes functionalized by COOH (SWNTs-COOH) nanocomposite scaffolds were fabricated through electrospinning. The effect of each component and different duration of cross-linking were assessed in terms of morphology, porosity, chemical structure, thermal behavior, mechanical properties, wettability, biodegradability, and in vitro cell culture study. Adding SWNTs-COOH decreased fiber diameter, water contact angle and degradation rate while increased tensile strength, hydrophilicity, stability and cell viability, due to their high intrinsic electrical conductivity, and mechanical properties and the presence of COOH functional groups in its structure. All the sample presented a porosity percentage of more than 80%, which is essential for tissue engineering scaffolds. The presence SWNTs-COOH did not have any adverse effect on cytocompatibility. The optimal cross-linking time increased the stability of the scaffolds in PBS. It can be concluded that the chitosan-gelatin/1wt% SWNTs-COOH scaffold can be appropriate for cartilage tissue engineering applications.     

Determining the effect of centrifugal and electrical forces on the jet behaviors,the nanofiber structure,and morphology

The increasing demand for nanofibers production has led to the rapid growth of the usage of electro‐centrifugal spinning (ECS) systems especially in recent years. Besides the rapid developments, fabrication of novel fibrous materials with novel techniques is still under investigation. Polyvinylepyrrolidone (PVP) is one of the multifunctional materials, which has attracted scientific interests to be employed in a variety of advanced applications. The main objective of the present study was therefore to explore the effects of essential parameters involved in fabrication of PVP nanofibers via an ECS system. The effects of rotational speed (197‐4051 r/min) and applied voltage (0‐14 kV) on the structural and morphological properties of nanofibers were also investigated. Analyses of the scanning electron microscope (SEM) images were performed with Digimizer and SPSS16.0 software to characterize the diameter distribution of the nanofibers. The degree of crystallinity was evaluated by the X‐ray diffraction method. In order to explain the unexpected results, further investigations were performed on the motion of the jet and flow rate. The results showed that instead of nanofibers, microparticles were formed at lower voltages and rotational speeds. The increase in the applied voltage resulted in a decrease in the minimum rotational speed that is required to form continuous fluid jet. The bending instabilities were changed from whipping to spiraling at the voltages above 10 kV. This resulted in the minimum fiber diameter at a voltage between 6 and 10 kV. Moreover, the applied voltage slightly affected the degree of crystallinity. No significant change was observed in the degree of crystallinity by varying the rotational speed.     

Molecular dynamics simulation of anticancer drug delivery from carbon nanotube using metal nanowires

In this study, we have investigated delivery of cisplatin as the anticancer drug molecules in different carbon nanotubes (CNTs) in the gas phase using molecular dynamics simulation. We examined the shape and composition of the releasing agent by using the different nanowires and nanoclusters. We also investigated the doping effect on the drug delivery process using N-, Si, B-, and Fe-doped CNTs. Different thermodynamics, structural, and dynamical properties have been studied by using the pure and different doped CNTs in this study. Our results show that the doping of the CNT has significant effect on the rate of the drug releasing process regardless of the composition of the releasing agent. © 2019 Wiley Periodicals, Inc.     

Synthesis of pyrrolo[2,3-d]pyrimidines (microreview)

Chemistry of Heterocyclic Compounds - Microreview summarizes recent methods for the synthesis of pyrrolo[2,3-d]pyrimidines, published since 2015. The methods are classified as Cu-catalyzed...     

原位生成的Ph3C+均相有机催化剂催化4,4’-芳亚甲基-二（3-甲基-1-苯基-1H-吡唑-5-醇）高效合成（英文）简

Trityl chloride (Ph₃CCl) efficiently catalyzes the condensation of 3-methyl-1-phenyl-1H-pyrazol- 5(4H)-one and aromatic aldehydes under mild and solvent-free conditions, affording 4,4''- (arylmethylene)-bis(3-methyl-1-phenyl-1H- pyrazol-5-ol)s in high to excellent yields and in short reaction time. The presence of the requisite organocatalytic trityl carbocation (Ph₃C⁺) species was confirmed by analysis of infrared, ¹H NMR, and ultra violet spectral data. A plausible mechanism was proposed for the reaction based on the observations and literature precedent.     

Nano-ferrous ferric oxide (nano-Fe3O4): Powerful,reusable, and stable catalyst for N-Boc protection of amines

Nano-ferrous ferric oxide (nano-Fe₃O₄) efficiently catalyzed N-boc protection of amines in high yields and acceptable reaction times. Nano-Fe₃O₄ was applied as an efficient, green, heterogeneous and reusable magnetite catalyst. Clean reaction, simple purification, short reaction time and high yield were some other advantages of this compound.     

Fluoroaziridines as novel substrates in the modified Petasis reaction: synthesis of monofluorinated propargyl amines

Reaction of 2-fluoroaziridines with potassium alkynyltrifluoroborates in the presence of BF₃·OEt₂ leads to fluorinated propargyl amines in moderate to good yields. The reaction proceeds as an in situ isomerization of 2-fluoroaziridines to α-fluorinated imines, followed by the reaction of the imine with alkynyldifluoroborane, which is generated in situ from the potassium alkynyltrifluoroborates and BF₃·OEt₂.