Tài liệu miễn phí Hoá học

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A water-soluble perylene derivative for live-cell imaging

Glutamic functionalized water-soluble perylene diimide, N, N’-di (l-glutamic amine)-perylene-3,4,9,10- tetracarboxylic diimide (GAPTCD) has three absorbance maxima at 469, 498, and 534 nm and two emission peaks at 550 and 587 nm. Owing to the highly negative electrostatic potential of the perylene plane, the perylene derivative showed good water solubility and strong fluorescence in alkali and neutral solutions. Both the absorbance and emission intensities decreased with the decreasing of pH from 9.66 to 5.92.

4/5/2023 5:25:48 AM +00:00

Conversion of racemic allylic hydroperoxides into corresponding chiral 1/2,3-triols by using catalytic OsO4 and chiral cinchona ligands in the absence of co-oxidant

For the first time, removal of oxygen atoms from allylic hydroperoxide functionality and reintroduction to the double bond was achieved using catalytic OsO4 and chiral cinchona alkaloid derivatives in an acetone–water mixture to give corresponding chiral 1/2,3-triol with an enantioselectivity up to 99% ee. The hydroperoxide group was used as both a co-oxidant and a source of hydroxyl groups. This protocol is thought to have potential to provide opportunities for chiral synthesis of 1/2,3-triols from corresponding allylic hydroperoxides in the absence of co-oxidant in one stage for the first time in the literature.

4/5/2023 5:25:40 AM +00:00

Enhanced electrocatalytic efficiency of C/MWNTs for methanol oxidation using Ni deposited on MWNTs

The power density of direct methanol fuel cells (DMFCs) can be changed by using different anode materials. Especially porous materials are preferred for the anode. In the present study, multiwall carbon nanotubes were first injected into graphite. Then, by depositing nickel, a catalyst was prepared for use as the anode material of the DMFC. This catalyst was named Ni@MWNTs. The oxidation of methanol and some kinetic parameters were investigated in KOH solution.

4/5/2023 5:25:31 AM +00:00

A case study on in vitro investigations of the potent biological activities of wheat germ and black cumin seed oil

The objectives of this study were to investigate the potential biological activities of black cumin seed oil (BCSO) and wheat germ oil (WGO) on different cell lines. Initially, commercially available BCSO and WGO obtained by supercritical carbon dioxide extraction were analyzed in terms of tocopherol, aliphatic alcohols, and thymoquinone content via HPLC and GC analysis. Cell free antioxidant activities and total phenolic content of both oils were detected by DPPH assay and Folin–Ciocalteu method, respectively.

4/5/2023 5:25:24 AM +00:00

Microwave-assisted regioselective [1,3]-dipolar cycloaddition of 3-methyl-2-(substitutedbenzylidene)-5-oxopyrazolidin-2-ium-1-ides to benzothiophene 1,1-dioxide

A series of pyrazolidinium ylides was reacted with benzothiophene 1,1-dioxide to afford (3R,5S,5aS,10bS)-3- methyl-5-substitutedphenyl-2,3,5,5a-tetrahydrobenzo[4,5]thieno[3,2-c]pyrazolo[1,2-a]pyrazol-1(10bH )-one 6,6-dioxides under microwave irradiation and their structures were identified by means of spectral/physical characteristics including X-ray diffraction data and HRMS measurements.

4/5/2023 5:25:16 AM +00:00

Synthesis and characterization of novel urea and thiourea substitute cyclotriphosphazene compounds as naked-eye sensors for F− and CN− anions

Novel hexakisurea and thiourea cyclotriphosphazene compounds (3–7) were synthesized. The structure of all compounds was identified using FT-IR 1H, 13C, and 31P NMR spectroscopy; MALDI-TOF MS; and elemental analysis. The optical sensor properties for anions of 3–7 were investigated using UV-Vis spectroscopy. It was determined that compounds 6 and 7 are spectrophotometric and naked eye sensors for F− and CN− anions, respectively. Sensor properties of these compounds for anions were investigated using UV-Vis spectroscopy. The stoichiometry of host–guest complexes was found to be 1:6.

4/5/2023 5:25:06 AM +00:00

Purification, refolding, and characterization of recombinant human paraoxonase-1

A high density lipoprotein (HDL)-linked enzyme with antioxidant and antiatherogenic properties, paraoxonase1(PON1), prevents the formation of atherosclerotic lesions in humans. In the present study, a recombinant hPON1 gene was produced using a small ubiquitin-related modifier (SUMO) fusion protein expression system. To that end, the hPON1 gene was amplified from human liver-ready cDNA, cloned into the expression vector pET SUMO, and expressed in Escherichia coli BL21 (DE3).

4/5/2023 5:24:59 AM +00:00

Synthesis of metal-free and metallophthalocyanines containing 18- and 21-membered macrocycles with mixed donor atoms and their metal-ion binding properties

This paper describes the synthesis of a series of metal-free phthalocyanines and metallophthalocyanines peripherally substituted by macrocycles of different ring sizes with the same donor atom sets. The effects of varying ring size of the macrocycle on the spectroscopic and metal ion binding properties of phthalocyanines were examined. For these purposes, electronic absorption properties for metal-free phthalocyanines and metallophthalocyanines were studied in dimethylformamide and tetrahydrofuran.

4/5/2023 5:24:52 AM +00:00

Optimization of the adsorption of a textile dye onto nanoclay using a central composite design

The main aim of this study was to evaluate the efficacy of montmorillonite clay for the adsorption of C.I. Basic Yellow 2 (BY2) dye from aqueous media. The experimental results were processed by response surface methodology based on a central composite design (CCD). The effect of four main variables, including initial BY2 concentration, adsorbent dosage, reaction time, and temperature on the removal of BY2 was evaluated by the model. The accuracy of the model and regression coefficients was appraised by employing analysis of variance.

4/5/2023 5:24:43 AM +00:00

Simultaneous analysis of losartan, its active metabolite, and hydrochlorothiazide in human plasma by a UPLC-MS/MS method

Quantitation was performed with multiple reaction monitoring in the negative ionization mode. The response of the method was linear over a dynamic range of 0.5–500, 1.0–750, and 0.25–150 ng/mL for LOS, EXP-3174, and HCTZ, respectively. Extent of signal suppression/enhancement was examined through postcolumn infusion. The effect of matrix components was evaluated by postextraction spiking and calculation of the slope of calibration lines. The method was successfully applied to a bioequivalence study of 50 mg losartan and 12.5 mg hydrochlorothiazide tablet formulation in 65 healthy human subjects. Reproducibility of the method was shown by reanalysis of 213 incurred samples.

4/5/2023 5:24:33 AM +00:00

Functional gold nanoparticle coated surfaces for CA 125 cancer biomarker detection

The immobilization method and atomic concentrations of Si 2p, Au 4f, S 2p, C 1s, N 1s, and O 1s of the resulting SA–biotin modified Si surface were determined by XPS. The CD spectrum and confocal microscopy imaging confirmed that step-by-step modification and bioconjugation can be monitored successfully. Such detailed and well-defined step-by-step characterization provides good information about the surface properties of biosensor platforms. In addition, the LSPR sensing ability of the Au Np based platforms was studied by using a model SA–biotin system.

4/5/2023 5:24:24 AM +00:00

Sustainable activity of hydrothermally synthesized mesoporous silicates in acetic acid esterification

Reaction experiments were also conducted in identical conditions in the presence of catalysts recovered after the reaction. The results indicated that sustainable activity could be achieved in the presence of these spent catalysts with activity losses around 10%. Evaluation of characterization analyses conducted with fresh and spent catalysts showed that the activity loss of SBA15-S catalysts had merely been due to STA leaching, whereas deformation of pore structure had occurred in MCM-41-S catalysts.

4/5/2023 5:24:17 AM +00:00

Acid-free synthesis of S-nitrosothiols at neutral pH by shock-freezing in liquid nitrogen

A laboratory method for the acid-free synthesis of S-nitrosothiols (RSNO) from NaNO2 and thiols in aqueous buffer of neutral pH is reported. Equimolar amounts of NaNO2 and thiol are added to a 100-µM Na 4EDTA-containing Na2HPO4 buffer (100 mM, pH 7.4). Samples are set into liquid nitrogen for 1 min and then thawed to room temperature or in an ice bath. Dependent upon the RSNO, repetition of the procedure may be required. This method may be of particular importance when the classical acid-based method fails or releases harmful gases such as H2S.

4/5/2023 5:24:10 AM +00:00

Green synthesis of 2-amino-7-hydroxy-4-aryl-4H-chromene-3-carbonitriles using ZnO nanoparticles prepared with mulberry leaf extract and ZnCl2

A highly efficient and environmentally benign protocol for the synthesis of 2-amino-7-hydroxy-4-aryl-4H-chromene-3-carbonitrile derivatives in good to high yields (77%–97%) by one-pot three-component coupling reaction of aromatic aldehydes, malononitrile, and resorcinol under reflux condition was developed in aqueous media using ZnO nanoparticles that were prepared in the presence of mulberry leaf extract under mild conditions.

4/5/2023 5:24:03 AM +00:00

Characterization of a Cu2+ -selective fluorescent probe derived from rhodamine B with 1,2,4-triazole as subunit and its application in cell imaging

A rhodamine B derivative containing 1,2,4-triazole as subunit was characterized as an “off–on” type Cu2+ - selective fluorescent probe. It exhibited high selectivity and sensitivity for Cu2+ in ethanol–water solution (9:1, v:v, pH 7.0, 20 mM HEPES) and underwent ring opening. A prominent fluorescence enhancement at 570 nm was observed in the presence of Cu2+ with the change in the absorption spectrum, and a 1:1 metal–ligand complex was formed.

4/5/2023 5:23:56 AM +00:00

Dinitrogen reduction on a polypyrrole coated Pt electrode under high-pressure conditions: electrochemical impedance spectroscopy studies

The electrochemical impedance spectroscopy (EIS) responses of a polypyrrole (PPy)-coated platinum electrode were investigated during N2 -reduction to ammonia in aqueous medium. Kinetic parameters such as film resistance, pore resistance, and double layer capacitance were analyzed as a function of applied potential and polymer film thickness. The relation between kinetic parameters was discussed by combining electrolysis results.

4/5/2023 5:23:47 AM +00:00

A new and simple procedure for the trace determination of mercury using differential pulse polarography and application to a salt lake sample

The procedure is simple: to a known amount of sulfite in the polarographic cell (HAc, pH 6 or 7) is added an unknown Hg(II) sample. The Hg(II) concentration is calculated simply from the decrease in the sulfite peak after reaction with Hg(II). The limit of detection was 1 × 10 −6 M (S/N = 3) in this medium, which could not be obtained with most other mercury determination methods. The proposed new method exhibits high selectivity, sensitivity, reproducibility, and accuracy.

4/5/2023 5:23:41 AM +00:00

Synthesis and characterization of halogen-containing aryl amide polymer-clay nanocomposites

Composites of BrPMAAm and FPMAAm monomers were obtained using 2%, 4%, 6%, and 10% organoclay by in situ polymerization. Molecular weights for poly(BrPMAAm), poly(BrPMAAm)-10%OSMT, poly(FPMAAm), and poly(FPMAAm)-10%OSTM were 91,300, 31,300, 17,400, and 23,700, respectively. Thermal properties of the nanocomposite were also developed when compared to the pure homopolymer. The beginning thermal decomposition temperature of nanocomposites was shifted to higher temperature. An exfoliated structure was found for the nanocomposites.

4/5/2023 5:23:33 AM +00:00

One-pot and solvent-free synthesis of 3-(9-hydroxy-3-methoxy-7-aryl-6,7,9,10- tetrahydro-5H-benzo[h]thiazolo[2,3-b]quinazolin-9-yl)-2H-chromen-2-ones and their antibacterial evaluation

All the synthesized compounds were characterized by spectral studies and screened for their in vitro antibacterial activity against S. aureus and B. thuringiensis (gram positive), and E. coli and K. pneumoniae (gram negative) bacterial strains. On comparing with the standard drug gentamicin, compounds derived from 4-methoxy and 3,4,5-trimethoxy benzaldehyde, i.e. 5g and 5h, showed broad spectrum antibacterial activity and the remaining compounds showed weak to moderate activity.

4/5/2023 5:23:27 AM +00:00

Kinetics study and influence of water-soluble polymer on the electrodeposition of iron from a citrate-chloride electrolyte on the basis of Fe(III)

The kinetics of the iron electrodeposition reaction from a plating bath containing trivalent iron ions is investigated in the present work. The electrochemical reaction is stated to proceed via the formation of relatively stable intermediates: Fe(II) ions. Only a part of the total amount of Fe(II) ions formed at the first stage of Fe(III) discharge is reduced further, producing metal iron. The effect of polyhexamethyleneguanidine hydrochloride (with an average molecular weight of 1000) on the iron deposition is ascertained.

4/5/2023 5:23:19 AM +00:00

Synthesis of bis-thiazoles, bis-pyrazoles, bis-hydrazonates, and bis-triazolothiadiazoles based on bis-hydrazonoyl and bis-hydrazones

A facile synthesis of bis-thiazoles, bis-pyrazoles, and bis-hydrazonates from the reaction of bis-hydrazonoyl dichlorides with different moieties is described. Bis-triazolothiadiazoles were synthesized via oxidative cyclization of bis-hydrazones. Structures of the final product were elucidated by elemental analyses and spectral data.

4/5/2023 5:23:12 AM +00:00

Preparation and characterization of polyaniline microrods synthesized by using dodecylbenzene sulfonic acid and periodic acid

The preparation of polyaniline (PANI) microrod arrays in the presence of dodecylbenzene sulfonic acid (DBSAH), a structure-directing agent, and in the presence of periodic acid (H5 IO6), an oxidant in aqua-acidic media, was investigated. DBSAH was performed to distinguish the roles of both surfactant and dopant. The method of preparation of DBSAH and H5 IO6 doped PANI (DBSAH–PANI) microrods in a reversed micelle had previously not been reported. The characterizations of the PANI microrods were determined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, (EDX) and X-ray diffraction (XRD).

4/5/2023 5:23:05 AM +00:00

Fabrication of silver nanoparticles in poly (N-isopropylacrylamide-co-allylacetic acid) microgels for catalytic reduction of nitroarenes

Poly(N-isopropylacrylamide-co-allyl acetic acid) [p(NIPAM-co-AAAc)] microgels were synthesized in aqueous medium by free radical emulsion polymerization using N-isopropylacrylamide as monomer, allylacetic acid as comonomer, and N,N-methylene-bis-acrylamide as cross-linker. Silver nanoparticles were fabricated inside the microgels by in situ reduction of silver ions. Microgels were analyzed by UV-visible spectroscopy, FTIR, XRD, TEM, and DLS. The formation of silver nanoparticles was confirmed by UV-visible spectroscopy. UV-visible spectra of the Ag-poly(Nisopropylacrylamide-co-allyl acetic acid) hybrid microgels showed a prominent absorption peak at about 411 nm.

4/5/2023 5:22:57 AM +00:00

The effect of temperature and concentration for methanol electrooxidation on Pt-Ru catalyst synthesized by microwave assisted route

At present, the methanol electrooxidation reaction (MOR) activities of carbon supported bimetallic Pt-Ru (M-PtRu@C) catalyst and monometallic Pt (M-Pt@C) catalysts prepared via microwave assisted polyol method and carbon supported Pt-Ru (P-PtRu@C) catalysts prepared by conventional polyol were examined to investigate the effect of the preparation method. These catalysts were characterized by X-ray diffraction, X-ray photo electron spectroscopy, and transmission electron microscopy (TEM).

4/5/2023 5:22:50 AM +00:00

Encapsulation of copper(II) complexes with three dentate NO2 ligands derived from 2,6-pyridinedicarboxylic acid in NaY zeolite

2,6-Pyridinedicarboxylic acid (H2 dipic) reacts with copper-exchanged zeolite NaY to form [Cu(dipic)(H2 O) 2 ] n , which is encapsulated in the pores of the zeolite. In this zeolite-encapsulated form, the copper derivative functions as an efficient catalyst for the oxidation of cyclohexene, toluene, cyclohexane, and ethyl benzene in the presence of hydrogen peroxide (as an oxidant). The catalyst was readily recovered from the reaction mixture, and it could be reused for an additional three runs without perceptible loss of activity.

4/5/2023 5:22:44 AM +00:00

Two new coordination polymers containing dicyanidoargentate(I) and dicyanidoaurate(I): synthesis and characterization, and a detailed in vitro investigation of their anticancer activities on some cancer cell lines

The antiproliferative and cytotoxic activities of C1 and C2 were significantly lower than those of free anions, indicating that the extreme cytotoxicity of free anions decreased to safe levels in C1 and C2. In conclusion, the results show that these novel compounds possess anticancer activities. The use of metals in medicine dates back to antiquity, with various complexes being used to treat different ailments. Even today, metal complexes and their application in medicine have been studied extensively.

4/5/2023 5:22:30 AM +00:00

Synthesis and biological evaluation of novel fused triazolo[4,3-a] pyrimidinones

The antimicrobial activity of the products was evaluated and the results revealed that compounds 8f and 15f showed strong activity against gram-positive bacteria while compound 15d showed the highest activity against gramnegative bacteria. Moreover, compounds 15b, 8d, 8e, 8c, 8l, and 8j exhibited significant antifungal activity. In addition, the antitumoral activity of the synthesized products against different cancer cell lines was determined and the results revealed that compound 12c was the most active against MCF-7, HepG-2, HCT-116, and HeLa with IC50 values of 0.51, 0.72, 0.95, and 0.95, respectively, as compared with doxorubicin as positive control.

4/5/2023 5:22:23 AM +00:00

Synthesis, characterization, biological studies, and molecular modeling of mixed ligand bivalent metal complexes of Schiff bases based on N -aminopyrimidine-2-one/2-thione

All the complexes showed nonelectrolytic behavior. Moreover, the newly synthesized mixed ligand complexes were evaluated for their in vitro antimicrobial efficiency against bacteria and yeast. The compound named Co(L1 L) had good antifungal activity against Candida species, but no profound antibacterial effect against bacterial strains. In addition, the ground state geometries of the complexes were optimized using a semi-empirical method at PM6 level, which is a suitable and effective basis set for organometallic and large structures to obtain information about their 3D geometries and electronic structures.

4/5/2023 5:22:16 AM +00:00

Kojic acid in organic synthesis

The reactions of kojic acid in organic synthesis are reviewed. The aim of this review is to cover the literature up to the end of 2014, showing the distribution of publications involving kojic acid chemistry in the synthesis of various pyrone containing compounds, pyridine and pyridone heterocycles, and also other organic compounds. First, introductory text about the preparation, biological, and industrial applications, and the chemical properties of kojic acid is given. Then its uses in organic synthesis are presented considering the reaction type.

4/5/2023 5:22:05 AM +00:00

Synthesis, characterization, and metal extraction studies of a new macrobicyclic ligand

This article describes the synthesis, characterization, and metal ion binding properties of a new macrobicyclic ligand. Solvent extraction experiments were performed in order to determine the extraction behavior of new macrobicyclic ligand towards selected metal cations. Selective extraction of heavy metals and precious metals is highly demanded due to their toxicity and commercial importance.

4/5/2023 5:21:58 AM +00:00