Tài liệu miễn phí Hoá học
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Multiwall carbon nanotube paste electrode as a sensor for sensitive determination of deferasirox in the presence of uric acid: Application for the analysis of pharmaceutical and biological samples
In this work, the electrochemical oxidation of deferasirox at a multiwall carbon nanotube paste electrode (MWCNTPE) was described. The electrochemical behavior of deferasirox was studied using cyclic voltammetry and chronoamperometry techniques and parameters such as charge transfer coefficient (α), the number of electrons involved in the rate-determining step (na), and diffusion coefficient (D) were calculated.
4/3/2023 10:11:00 PM +00:00
Synthesis and biological evaluation of novel chalcones bearing morpholine moiety as antiproliferative agents
In this research, a new series of (E) -3-(4-substitutedphenyl)-1-(4’-morpholinophenyl)prop-2-en-1-one derivatives 1–7 was synthesized, aiming to develop effective antiproliferative agents. The antiproliferative activities of compounds 1–7 were examined against HeLa and C6 cell lines at eight different concentrations using the BrdU ELISA assay. The activity results were compared with reference anticancer drug 5-fluorouracil (5-FU). Compound 1 had almost the same antiproliferative activity as 5-FU. Compounds 1–7 were found to have greater effects against the C6 cell line than the HeLa cell line.
4/3/2023 10:10:52 PM +00:00
Influence of manganese content on the supercapacitive performance of PbO2–MnO2 electrodes
PbO2–MnO2 electrodes were prepared by electrochemical codeposition methods. The electrodes were characterized by scanning electron microscope, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The content of manganese in the electrodes increased with the increase in manganese ion concentration in the solution, which can reach 48.4%. The codeposition of manganese decreased the grain sizes and formed the porous structure. Cyclic voltammetry and galvanostatic charge–discharge measurements were used to evaluate the influence of manganese content in the electrodes on the specific capacitive performance of PbO2–MnO2 electrodes.
4/3/2023 10:10:43 PM +00:00
Application of a pencil graphite electrode for voltammetric simultaneous determination of ascorbic acid, norepinephrine, and uric acid in real samples
A pencil graphite electrode (PGE) was used for the simultaneous detection of ascorbic acid (AA), norepinephrine (NE), and uric acid (UA) by differential pulse voltammetry and cyclic voltammetry. The anodic peaks of AA, NE, and UA in their mixture can be well separated in 0.1 M Britton–Robinson buffer solution at pH 4.0. The effects of various experimental parameters such as pH, scan rate, and voltammetric parameters on the voltammetric response of these compounds were investigated. Under optimum conditions, linear calibration graphs were obtained from the AA, NE, and UA concentration ranges, which were 100–800 nM, 20–170 nM, and 40–175 nM, respectively.
4/3/2023 10:10:36 PM +00:00
Application of the Taguchi approach to optimize ZnO synthesis via hydrothermally assisted sol-gel method
ZnO powder was synthesized via a hydrothermally assisted sol-gel method. Synthesis variables including Znprecursor type, pH value, time, and temperature of hydrothermal treatment were analyzed using the Taguchi approach. The experimental procedures were defined based on the L9 array for four variables in three levels. The influences of those variables on the response parameters, i.e. crystallite size, crystallinity, band gap energy (Eg), and degradation constants (k), were evaluated. XRD results and Eg values showed that ZnO wurtzite appeared to be the only crystalline phase in the samples.
4/3/2023 10:10:25 PM +00:00
Electrochemical polymerization of a new alkoxy-bridged dithieno (3,2-B:2’,3’-D) pyrrole derivative
A novel alkoxy-bridged dithieno (3, 2-B:2’,3’-D) pyrrole (DTP) derivative was synthesized and its corresponding polymer poly(1,2-bis(2-(4H-dithieno[3,2-b:2’,3’-d]pyrrol-4-yl)ethoxy)ethane) (P(DTP-alkoxy-DTP)) was successfully obtained electrochemically. The effects of alkoxy bridge in the structure on the electrochemical and spectroelectrochemical properties of the polymer were also investigated in detail. The results showed that the polymer film exhibits multielectrochromic behavior and a low band gap of 1.82 eV.
4/3/2023 10:10:18 PM +00:00
A novel hypobromous acid scavenging activity assay using p-cresol as a spectrofluorometric probe
In this study, a novel spectrofluorometric assay based on p-cresol (4-methyl phenol) probe is developed for the measurement of HOBr scavenging activity. It is the first study involving the use of a p-cresol probe for the determination of the HOBr scavenging activity of biothiols. While the p-cresol probe (λex = 260 nm, λem = 305 nm) has fluorescence characteristics, its brominated derivatives emerging at the end of the oxidation reaction with HOBr do not show fluorescence. The initial fluorescence intensity of the p-cresol probe is decreased in the presence of the brominating agent, HOBr, and this decrease is lower in the presence of HOBr scavenging antioxidants.
4/3/2023 10:10:11 PM +00:00
Oxime-containing acetylcholinesterase reactivators and their complexes with Pd(II) and Pt(II) ions: Recent developments
The ability of oxime-containing acetylcholinesterase reactivators BT-07 (K005), BT-08 (K033), BT-07-4M (K074), and obidoxime (H2LX2, X = Cl−, Br−) to bind palladium(II) or platinum(II) cations was evaluated in aqueous solutions (pH 7.4) at metal-to-ligand molar ratio varying from 1:10 to 10:1. Spectral changes were monitored within a week after mixing the reagents in the range from 220 nm to 500 nm. Results showed that depending on chemical structure and reaction time, oximes form two complex species of composition, [MHL]3+ or [M2L]4+ (M = Pd(II), Pt(II)). It was also found that complexation of platinum(II) ions proceeds slower as compared to palladium(II).
4/3/2023 10:10:04 PM +00:00
Synthesis, biological evaluation, and in silico study of some unique multifunctional 1,2,4-triazole acetamides
The imperative demand for antibacterial agents and enzyme inhibitors prompted us to synthesize some new compounds, 6a–6k, bearing multifunctional moieties. The target acetamides were derived from 4-phenyl-5-(1- tosylpiperidin-4-yl)-4H-1,2,4-triazole-3-thiol (3). The structural analysis was carried out using modern spectroscopic techniques including IR, NMR, and EIMS spectral analysis. The antibacterial activity was screened against five bacterial strains including three gram-negative and two gram-positive ones. Enzyme inhibition was carried out against lipoxygenase enzyme and results were supported by in silico study. The synthesized compounds were proved to be potent antibacterial agents and enzyme inhibitors.
4/3/2023 10:09:54 PM +00:00
PEG-peptide conjugate containing cathepsin B degradation unit as a doxorubicin carrier system
A drug delivery system (DDS) containing a cathepsin B degradable sequence and pH-responsive histidines was prepared by methoxypolyethylene glycol and peptide conjugation. Doxorubicin was attached to the carrier system using amide linkage to give the final form of the DDS, denoted as mPEG-AT3-DOX. mPEG-AT3-DOX exhibited a bimodal size distribution at about 15 and 30 nm independent of pH, whereas the size of the control DDS containing no peptide sequence, mPEG-DOX, was measured as ∼ 15–20 nm. At the end of 72 h, % doxorubicin release from both of the DDSs was observed to be below 8.5 ± 3% in the absence of cathepsin B, and it increased to 17 ± 2% in the presence of cathepsin B for mPEG-AT3-DOX.
4/3/2023 10:09:46 PM +00:00
Nickel(II)-PPh3 complexes with ONS and ONN chelating thiosemicarbazones: Synthesis and inhibition potential on influenza A viruses
Tetra-coordinated nickel(II) complexes of two ONS (1, 2) and seven ONN (3a–3g) chelating 2-hydroxy3-methoxy-benzaldehyde thiosemicarbazones were synthesized. The dibasic ligands and complexes bearing PPh 3 as a coligand were characterized by means of analytical and spectroscopic data. Cytotoxic activities of the ligands and nickel(II) complexes were determined using the MTT assay in vitro against MDCK cells, and then all the compounds were tested on influenza virus replication by plaque assays. The compounds showed GI 50 values varying from concentrations of 15.9 up to 161.8 µ g/mL for MDCK cells.
4/3/2023 10:09:36 PM +00:00
Protein ion-exchange chromatography on a biomacromolecule-immobilized monolithic cryogel
An efficient and inexpensive monolithic stationary phase (PHEMA-HA) has been prepared through an easy process comprising addition of humic acid (HA) to a mixture of 2-hydroxyethyl methacrylate (HEMA) and N,N’- methylenebisacrylamide (MBAAm) and subsequent radical-polymerization at –20 ◦ C. The prepared monolithic material was characterized in terms of various techniques and methods such as elemental analysis, FTIR spectroscopy, scanning electron microscopy, mercury porosimetry, hydrolytic stability tests, pHpzc measurements, water-holding capacity, and water permeability. The amount of HA incorporated into the structure was calculated as 45 mg/g from the elemental analysis results.
4/3/2023 10:09:26 PM +00:00
Development of a molecularly imprinted polymer-based electrochemical sensor for tyrosinase
For the first time a molecularly imprinted polymer (MIP)-based sensor for tyrosinase is described. This sensor is based on the electropolymerization of scopoletin or o-phenylenediamine in the presence of tyrosinase from mushrooms, which has a high homology to the human enzyme. The template was removed either by treatment with proteinase K or by alkaline treatment. The measuring signal was generated either by measuring the formation of a product by the target enzyme or by evaluation of the permeability of the redox marker ferricyanide. The o-phenylenediamine-based MIP sensor has a linear measuring range up to 50 nM of tyrosinase with a limit of detection of 3.97nM (R2 = 0.994) and shows good discrimination towards other proteins, e.g., bovine serum albumin and cytochrome c.
4/3/2023 10:09:18 PM +00:00
The synthesis of new oxindoles as analogs of natural product 3,3′ -bis(indolyl)oxindole and in vitro evaluation of the enzyme activity of G6PD and 6PGD
Natural and synthetic derivatives that contain an indole core are being used in medical treatments and technological processes. Therefore, the development of new synthetic methods for the synthesis of indole derivatives is very popular. In this study, new oxindoles with reaction of 4,7-dihydro-1H -indole (2) and isatin (4) were synthesized as analogs of natural product 3,3′ -bis(indolyl)oxindole. The biological properties of the compounds obtained during this study were also studied, showing that compounds 5, 7, and 12 inhibited the activity of G6PD with an IC50 of 99 µM, 231 µM, and 304 µM respectively.
4/3/2023 10:09:07 PM +00:00
A new member of Mo36- polyoxoanion’s family: Synthesis, crystal structure, and physico-chemical properties of K10[Mo36O110(OH)6(H2O)12].38H2O
The new giant Mo 36 polyoxomolybdate formulated as K10[Mo36O110(OH)6(H2O)12].38H2O (1) was isolated by conventional solution method by the reaction of K2 MoO4 and KNO3 in aqueous solution (pH = 1.8), at room temperature, and structurally characterized by single-crystal X-ray diffraction methods. The title compound crystallized in the monoclinic system, space group P21/n with unit a = 16.5180 (0)˚A, b = 18.4485 (0)˚A, c = 24.2424 (0)˚A, α = 90.00◦, β = 99.51◦, γ = 90.00◦, V = 7285.79 (0)˚A3, and Z = 2. The refinement of the structure led to a residual factor R = 0.061 for 15,676 reflections.
4/3/2023 10:09:00 PM +00:00
Synthesis and biological properties of novel 1-methyl-2-(2-(prop-2-yn-1-yloxy)benzylidene) hydrazine analogues
1-Methyl-2-(2-(prop-2-yn-1-yloxy)benzylidene)hydrazine analogues were readily prepared in good yields by the reaction of 2-(prop-2-yn-1-yloxy)benzaldehydes and methyl hydrazine. The reaction tolerates a variety of substituents on the 2-hydroxybenzaldehyde to form nitro-, halo-, methoxy-, and naphthyl-substituted 1-methyl-2-(2-(prop-2-yn-1- yloxy)benzylidene)hydrazines. The in vitro antioxidant capacity measurements revealed that among all the analyzed hydrazine analogues that surpassed the Trolox standard, 1-(2-(but-3-ynyl)-5-nitrobenzylidene)-2-methylhydrazine had the maximum value, which was approximately 1.7 times that of Trolox.
4/3/2023 10:08:51 PM +00:00
Voltammetric determination of vanillin in commercial food products using overoxidized poly(pyrrole) film-modified glassy carbon electrodes
In this work, a very simple, rapid, cheap, sensitive, and selective polymer film-modified electrode for vanillin determination in commercial food products was developed via electrochemical polymerization and overoxidation of pyrrole. The formation of both poly(pyrrole) and overoxidized poly(pyrrole) films on a glassy carbon electrode surface was characterized by electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Under optimized conditions, the calibration graph comprises two linear segments of 0.032–1.500 µmol L−1 and 3.00–150.00 µmol L−1 with a detection limit of 0.012 µmol L−1 . The selectivity of the modified electrode was examined in the presence of metals, inorganic ions, and organic substances.
4/3/2023 10:08:41 PM +00:00
Spectroscopic and thermodynamic approach to the interaction of nonperipherally substituted cationic phthalocyanines with calf thymus (CT)-DNA
Novel, nonperipherally tetrasubstituted cationic metal-free and metallophthalocyanines (Zn, In) were synthesized in the present study. The binding constants, the disappearance of quenching effect of all cationic phthalocyanines on the fluorescence intensity of SYBR Green–disodium salt of deoxyribonucleic acid (DNA) from calf thymus complex, and the changes in Tm of double helix DNA with thermal denaturation profile were investigated by UV-Vis and fluorescence spectrophotometric methods. To investigate the spontaneity of the reactions between DNA and novel quaternized phthalocyanines in buffer, thermodynamic parameters were employed.
4/3/2023 10:08:30 PM +00:00
Transfer of the protonable surfactant dipalmitoyl-phosphatidylcholine across a large liquid/liquid interface: A voltammetric study
Adsorption behavior of the zwitterionic phospholipid dipalmitoyl-phosphatidylcholine (DPPC) at the polarizable liquid/liquid interface formed between water and 1,2-dichloroethane electrolyte solutions is studied taking into account both the pH of the aqueous phase and the concentration of the phospholipid in the organic phase by cyclic voltammetry. Experimental results showed that the adsorption of the phospholipid strongly depends on the pH of the aqueous phase, which determines the surface ionization of the polar head of the phospholipid molecule and hence the stability of the adsorbed layer of phospholipids.
4/3/2023 10:08:23 PM +00:00
Simultaneous determination of copper(II) and zinc(II) via simple acid-base titrimetry using glass pH electrode
The combination of potentiometric methods with multivariate calibration techniques allows complex mixtures to be analyzed. In this study, a new method was developed and reported for simultaneous determination of copper(II) and zinc(II) cations in a mixture by titrimetric methods. The developed method permits simultaneous cation analysis with low detection limits, just by using a pH electrode. This work has achieved the challenging goal of developing a cost-effective and applicable method that can be applied in most laboratories due to independence of any chemical instruments. Partial least squares 1, one of the multivariate calibration techniques, was used in the analysis of titrimetric data.
4/3/2023 10:08:14 PM +00:00
Effect of pH and β -cyclodextrin on the photophysical properties of lamotrigine
Photophysical properties of lamotrigine (LMT) were investigated at different pH values. Lamotrigine exhibited a broad absorption band at 308 nm that was shifted to 268 nm at pH 2.0 due to protonation (HLMT+). Emission spectra of LMT at different pH values showed a single band at 483 nm except for at pH 2.0, where a second band at 502 nm was observed due to the deprotonation from the singlet excited state. LMT pH profile was used to calculate pK a of LMT in excited and ground states (pK a* = 4.50 and pK a = 5.90). Absorption spectra of LMT at different pH values for LMT in the presence of β-CD showed an isosbestic point at 290 nm. A significant enhancement in the emission intensity of LMT upon increasing β-CD (0–7 mmol L−1 ) was reported.
4/3/2023 10:08:06 PM +00:00
Tetrahydronaphthalene as a precursor of new series of chalcones, flavanones, and flavones
An efficient synthetic route for a novel series of chalcones 2a–2d as well as for the corresponding flavanones 3a–3d and flavones 4a–4d, using functionalized tetrahydronaphthalene (THN), is described herein. The Claisen– Schmidt condensation of such THN and aromatic aldehydes, in the presence of an aqueous solution of KOH (40%), selectively gives the expected chalcones 2a–2d, which may further undergo an intramolecular oxa-Michael addition using piperidine, affording the corresponding flavanones 3a–3d in high yields.
4/3/2023 10:07:52 PM +00:00
Experimental and theoretical studies of carbazole-based Schiff base as a fluorescent Fe3+ probe
Synthesis of a new (E)-N1-((9-ethyl-9H-carbazol-3-yl)methylene)-5-nitrobenzene-1,2-diamine as a fluorescent chemosensor for selective detection of Fe3+ ion over a number of other metal ions is described. The method for the synthesis of the carbazole Schiff base was based on the condensation of carbazole-3-carbaldehyde with 4-nitro-ophenyldiamine in dimethylformamide in a moderate yield. The structure of the final compound was characterized by 1H NMR, 13C NMR, IR, mass spectrometry, and single crystal X-ray diffraction. The final compound exhibited exceptional selective and sensitive turn-on fluorescence response to the Fe3+ cation.
4/3/2023 10:07:44 PM +00:00
Sodium borohydride for the near-future energy: A “rough diamond” for Turkey
Boron-based materials are potential solutions in the field of energy. They have been regarded as hydrogen storage materials, liquid fuels of direct liquid-fed fuel cells (DLFCs), electrolytes of battery, and/or energetic substances. A typical example is sodium borohydride (NaBH4). In sodium hydroxide-stabilized aqueous solutions, it is seen as an efficient H2 generator or a performing fuel of DLFCs. Actually, it plays a wider role; it is also the precursor of several boron-based materials of interest in the field of energy. In other words, it is indirectly considered for other energy applications, i.e. solid electrolytes of all solid-state batteries and hypergolic fuel.
4/3/2023 10:07:23 PM +00:00
Cu(II) immobilized on Fe 3O4@Agarose nanomagnetic catalyst functionalized with ethanolamine phosphate–salicylaldehyde Schiff base: A magnetically reusable nanocatalyst for preparation of 2-substituted imidazolines, oxazolines, and thiazolines
Herein we synthesized Cu(II) immobilized on Fe 3 O4 @Agarose functionalized with ethanolamine phosphate– salicylaldehyde Schiff base (Fe 3 O4 @Agarose/SAEPH2 /Cu(II)) as a new and cost-effective nanomagnetic catalyst. The nanomagnetic catalyst was characterized by FT-IR, XRD, VSM, SEM-EDX, TEM, TGA, and ICP techniques and it was found that the particles were about 9–25 nm in size and spherical with entrapment of the Fe 3 O4 particles in the hollow pore structure of the agarose. The prepared nanomagnetic catalyst showed excellent activity for preparation of 2-substituted imidazolines, oxazolines, and thiazolines.
4/3/2023 10:07:06 PM +00:00
Kinetics of silver(I)-catalyzed oxidation of allyl alcohol by peroxodiphosphate in acetate buffers
The kinetics and mechanism of silver(I)-catalyzed oxidation of allyl alcohol with peroxodiphosphate in acetate buffers have been studied. The rate is independent of allyl alcohol concentration. The effect of other reaction parameters such as hydrogen and acetate ions has also been studied. The rate law accounting for all experimental observations corresponds to the proposed mechanism. The energy and entropy of activation have also been evaluated by employing Eyring plots.
4/3/2023 10:06:58 PM +00:00
Biological study on novel coumarinyl 1,3,4-oxadiazoles
Coumarinyl 1,3,4-oxadiazoles were synthesized from Schiff bases and acetic anhydride. All compounds were characterized by melting points and their structures confirmed by mass and 1H and 13C NMR spectrometry. These novel coumarinyl derivatives were subjected to antibacterial, antifungal, antaflatoxigenic, and antioxidant activity. Their activity varied depending on their structure, where 2-(3-acetyl-5-(((4-methyl-2-oxo-2 H -chromen-7-yl)oxy)methyl)- 2,3-dihydro-1,3,4-oxadiazol-2-yl)-1,4-phenylene diacetate showed significant antioxidant and antibacterial activity on B. subtilis. 4-(3-Acetyl-5-(((4-methyl-2-oxo-2H -chromen-7-yl)oxy)methyl)-2,3-dihydro-1,3,4-oxadiazol-2-yl)-1,2-phenylene diacetate was found to possess excellent antifungal and antiaflatoxigenic activity.
4/3/2023 10:06:46 PM +00:00
Nanocapsulation of herbicide Haloxyfop-R-methyl in poly(methyl methacrylate): Phytotoxicological effects of pure herbicide and its nanocapsulated form on duckweed as a model macrophyte
In the present study the nanocapsulation of Haloxyfop-R-methyl in poly(methyl methacrylate) was successfully performed. Poly(methyl methacrylate)/Haloxyfop-R-methyl nanocapsules were synthesized using a miniemulsion method and their surface morphology was studied by scanning electron microscopy and transition electron microscopy. The chemical characterization of nanocapsules was done by FT-IR spectroscopy. The herbicide loading and encapsulation efficiency were also analyzed for the herbicide-loaded nanocapsules. In order to evaluate the toxic effects of nanocapsulated herbicide and pure herbicide on Lemna minor L., some physiological effects of these two compounds were investigated.
4/3/2023 10:06:36 PM +00:00
Physicochemical characterization of a polymeric conductor: Application to defluoridation of industrial effluent by electrodialysis
In many places around the world, the fluoride concentration in ground water as raw water is higher than the threshold standard for healthy drinking water. The aim of this work is to study the characteristics of an anionic membrane that will be the subject of an application for defluoridation by electrodialysis. The first objective of this work is to evaluate the physicochemical characteristics of the membrane used in experiments by determination of the exchange capacity, water uptake, ionic conductivity, and transport number (Hittorf method). The second part consists of studying the effect of different parameters such as electrodialysis time.
4/3/2023 10:06:28 PM +00:00
Gas permeability of polydimethylsiloxane membranes filled with clinoptilolite in different cationic forms
Zeolite-polymer mixed matrix membranes were prepared by filling polydimethylsiloxane (PDMS) with clinoptilolite in various cationic forms of K, Mg, H, and Na. The membranes were characterized by scanning electron microscopy as well as measurements of O2, N2, and CO2 gas permeabilities. The results indicated the presence of an optimum zeolite loading in the mixed matrix membranes maximizing permeability. The type of the cationic form of clinoptilolite used affected the permeabilities and ideal selectivities of the zeolite-polymer mixed matrix membranes investigated to some degree and some improvements were obtained when compared to the ideal selectivities of the original polymeric membranes.
4/3/2023 10:06:20 PM +00:00