Turkish Journal of Chemistry最新文献

The cofactor of a class A monooxygenase is reduced at an external location of the enzyme and is subsequently pulled back into the active site after the reduction. This observation brings the question; is there any defense mechanism of the active site of a monooxygenase against the formation of the harmful hydrogen peroxide from the reactive C(4a)-(hydro)peroxide intermediate? In this study, the barrier energies of one to three water molecule-mediated uncoupling reaction mechanisms in water exposed reaction conditions were determined. These were found to be facile barriers. Secondly, uncoupling was modeled in the active site of kynurenine 3-monooxygenase complex which was represented with 258 atoms utilizing cluster approach. Comparison of the barrier energy of the cluster model to the models that represent the water exposed conditions revealed that the enzyme does not have an inhibitory reaction site architecture as the compared barrier energies are roughly the same. The main defense mechanism of KMO against the formation of the hydrogen peroxide is deduced to be the insulation, and without this insulation, the monooxygenation would not take place as the barrier height of the hydrogen peroxide formation within the active site is almost half of that of the monooxygenation.

Both environmental and economic disadvantages of using petroleum-based products have been forcing researchers to work on environmentally friendly, sustainable, and economical alternatives. The purpose of this study is to optimize the solvothermal liquefaction process of grape pomace using response surface methodology coupled with a central composite design. After investigating the physicochemical properties of the liquified products (biopolyol) in detail, a bio-based rigid polyurethane foam (RPUF) was synthesized and characterized. The hydroxyl and acid numbers and viscosity values of all the biopolyols were analyzed. According to variance analysis results (%95 confidence range), both the reaction temperature and catalyst loading were determined as significant parameters on the liquefaction yield (LY). The model was validated experimentally in the following reaction conditions: 4.25% catalyst loading, 50 min reaction time, and 165 °C reaction temperature, which yields an LY of 81.3%. The biopolyols produced by the validation experiment display similar characteristics (hydroxyl number: 470.5 mg KOH/g; acid number: 2.31 mg KOH/g; viscosity: 1785 cP at 25 °C) to those of commercial polyols widely preferred in the production of polyurethane foam. The physicochemical properties of bio-based foam obtained from the biopolyol were determined and the thermal conductivity, closed-cell content, apparent density, and compressive strength values of bio-based RPUF were 31.3 mW/m·K, 71.1%, 33.4 kg/m³, and 105.3 kPa, respectively.

The usability of polyvinyl chloride-based quaternary triethanol ammonium chloride anionite (PVC-TEAC) as a potential extractant for tungstate was investigated to recover tungstate from Gabal Qash Amir, Egypt, assaying 70.91% WO₃. Structure elucidation for PVC-TEAC anionite was successfully carried out using several techniques. Experimental measurements, such as pH, agitation time, initial tungsten concentration, anionite dose, co-ions, temperature, and eluting agents, have been optimized. It was found that PVC-TEAC anionite has a maximum capacity of 63 mg per gram. From the distribution isotherm modeling, Langmuir's model fits the experimental results better than Freundlich's, with a theoretical value of 61.728 mg g^-1. According to kinetic modeling, the first- and second-order modeling may be regarded as a mixed modeling for a successful adsorption system. Thermodynamic prospects reveal that the adsorption process was predicted as an exothermic, spontaneous, and preferable adsorption at low temperatures. Tungsten ions can be eluted from the loaded anionite, by 1M H₂SO₄ with a 97% efficiency rate. It was found that PVC-TEAC anionite reveals good separation factor (S.F.) towards most of co-ions. A successful Alkali fusion with NaOH flux followed by tungstate recovery by PVC-TEAC anionite is used to obtain a high-purity tungsten oxide concentrate (WO₃), with a tungsten content of 78.3% and a purity of 98.75%.

This research aims to examine the transdermal release of water-soluble indium and zinc metallo phthalocyanine (InPc and ZnPc) compounds from the poly(vinyl alcohol) (PVA) membrane and the cytotoxicity effect of these Pcs on normal mouse fibroblasts (L929 fibroblast) and human melanoma (SK-MEL-30) cells. For this purpose, the effects of temperature, pH, drug concentration and membrane thickness on transdermal release were investigated in order to obtain the optimum transdermal release profile by preparing PVA membranes with different thicknesses and crosslinked by heat treatment. Optimum drug release was found to be 85.36% using 6 μm thick PVA membrane at 37 ± 0.5 °C, when upper cell pH 1.2 and lower cell pH 5.5, for 3 mg/mL InPc drug concentration. Under the same conditions, the drug release value for ZnPc was found to be 69.78%. In addition, in vitro studies were performed on L929 and SK-MEL-30 cells. under optimized drug (InPc and ZnPc) and membrane conditions. It was found that no significant cytotoxic effect was observed in L929 and SK-MEL-30 cells in the dark. Photodynamic tests were also carried out with InPc and ZnPc. The results show that cell viability decreases in SK-MEL-30 cells at concentrations of 10 μg/mL and above. In addition, while the InPc IC50 value was determined as 4.058 μg/mL, this value was determined as 11.574 μg/mL for ZnPc.

In this study, we developed a heterojunction photocatalyst, namely nitrogen-doped carbon quantum dots/titanium dioxide (N-CQDs/TiO₂), for the effective and sustainable treatment of ciprofloxacin (CIP) antibiotic in aqueous solution. First, N-CQDs were prepared from a chitosan biopolymer with a green, facile, and effective hydrothermal carbonization technique and then anchored on the TiO₂ surface via a hydrothermal process. The morphological, structural, and optical properties of the as-prepared materials were characterized by using advanced analytical techniques. The impacts of the mass percentage of N-CQDs, catalyst and CIP concentration, and pH on photocatalytic CIP degradation were investigated in depth. Comparative analyses were performed to evaluate different processes including adsorption, photolysis, and photocatalysis for the removal of CIP with TiO₂ and N-CQDs/TiO₂. The results revealed that N-CQDs/TiO₂ exhibited the highest CIP removal efficiency of up to 83.91% within 120 min using UVA irradiation under optimized conditions (10 mg/L CIP, 0.4 g/L catalyst, and pH 5). Moreover, the carbon source used in the fabrication of N-CQDs was also considered, and lower removal efficiency was obtained when glucose was used as a carbon source instead of chitosan. This excellent improvement in CIP degradation was attributed to the ideal separation and migration of photogenerated carriers, strong redox capability, and high generation of reactive oxygen species provided by the successful construction of the N-CQDs/TiO₂ S-scheme heterojunction. Scavenger experiments indicated that h⁺ and •OH reactive oxygen species were the predominant factors for CIP elimination in water. Overall, this study presents a green synthesis approach for N-CQDs/TiO₂ heterojunction photocatalysts using natural materials, demonstrating potential as a cost-effective and efficient method for pharmaceutical degradation in water treatment applications.

Abies is an important genus of the family Pinaceae, with about 50 species found in the highlands of Asia, Europe, North Africa, and North and Central America. The principal aim of the present work was to investigate the chemical content and biological potential of the resin and cone from Abies nordmanniana subsp. bornmulleriana and Abies nordmanniana subsp. equi-trojani, respectively. The flavonoid and phenolic contents of the resin and cones were evaluated using liquid chromatography-high resolution mass spectrometry (LC-HRMS). Additionally, the essential oil and fatty acid compositions were analyzed using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID), respectively. Cytotoxicity of the extracts and essential oils were screened against certain cancer cell lines, namely, human prostate adenocarcinoma cell line (PC3), human lung adenocarcinoma cell line (A549), human pancreatic cancer cell line (PANC-1), human hepatocellular carcinoma cell line (HepG2), human breast cancer cell line (MDA-MB231), and normal human lung fibroblast cell line (CCD-34-LU), with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay. According to the MTT results, hexane extracts of both cone (CH) and resin (RH), ethanol-water (CEW), dichloromethane (CD), and acetone (CA) extracts of the cone mostly inflict cytotoxicity in HepG2 cell line. Antiviral activities of Abies nordmanniana subsp. extracts at doses of 5 μg/g and 10 μg/g were also evaluated in ovo for their virucidal activity against avian coronavirus. Abies nordmanniana subsp. extracts exhibited concentration-dependent antiviral activity on specific pathogen-free embryonated chicken eggs. Significantly, cone acetone extract (CA), cone ethanol extract (CE), and cone dichloromethane extract (CD) of Abies nordmanniana subsp. exhibited strong inhibition of the virus at a concentration of 10 μg/g. The most potent virucidal activity was observed with ethanol-water extract of conifer form (CEW). According to these results, it was proved that Abies nordmanniana species could be a potential, sustainable, and renewable drug source, especially considering the impressive antiviral and significant cytotoxic activity potentials.

A practical, rapid, and efficient method for the synthesis of azoindolizine derivatives via aryldiazonium salts with excellent yields was reported. Firstly, the corresponding aniline derivatives were synthesized via a simple and rapid method. Then, the optimal reaction conditions were investigated using a variety of protic and aprotic solvents that demonstrating the robustness of the approach. Finally, the applicability of this method to various sources of indolizine and phenyldiazonium tetrafluoroborate salts was expanded.

Garlic is in the family Liliaceae and has many different constituents such as organic sulfur compounds, amino acids, carbohydrates, minerals, and vitamins. In this work, a simple, sensitive, and accurate analytical method was developed for the determination of selected organosulfur compounds (OSCs) in garlic bulbs using reversed phase-high performance liquid chromatography (RP-HPLC). Oil-soluble and water-soluble OSCs were extracted from the garlic samples via acetonitrile and deionized water, respectively. The OSCs were separated on a Phenomenex C18 (250 mm, 4 mm, 5mm) column and the monitoring was performed with a UV detector at 220 nm. An isocratic mobile phase comprising of 0.10 M trifluoroacetic acid (TFA) in 85% acetonitrile (ACN) and 0.10 M TFA in distilled water (DW) (90: 10% v/v) was used to elute the analytes. Under optimum experimental conditions, the limits of detection (LOD) for the analytes were calculated in the range of 0.09 to 0.17 mg/kg. For the garlic sample extracts analyzed under optimal instrumental conditions, DAS (diallyl sulfide), DADS (diallyl disulfide), and DATS (diallyl trisulfide) were detected in the ranges of 8.0 to 32.5 mg/kg, 20.4 to 67.3 mg/kg, and 60.7 to 356.6 mg/kg, respectively. Spiked recovery experiments were conducted on the garlic samples to confirm the method's applicability and accuracy. The recovery results ranged between 39.0% and 90.9% for the garlic samples extracted with deionized water. The developed method is simple, precise, accurate, reliable, and time-effective for the determination of OSCs. Additionally, the green profile of the developed method was investigated by using AGREEprep software and the greenness score was recorded as 0.65, indicating that the method developed is environmentally friendly.

The fabrication of few-layer borophene (BP) from bulk boron (b-B) is of great importance and still a scientific challenge due to the complex structure and crystallinity of b-B. Herein, we propose a novel technique to prepare a few-layer BP on a large scale with a large lateral size in a well-controlled manner. For this, we employed the Hummers' method-assisted liquid-phase exfoliation. In the first step, the chemical exfoliation of the b-B as a precursor was performed by the modified Hummers' method. After chemical exfoliation, mechanical delamination was employed by using an immersion sonicator. Finally, BP sheets were collected with dimensions ranging from several hundred nanometers to a few micrometers and an average thickness of 4.2 nm. We envision that the proposed low-cost, flexible, and large-scale production method will provide unique advantages for the application of few-layer BP in the realization of high-performance electronics, optoelectronics, flexible devices, sensing systems, energy conversion, and storage devices.

A hyperbranched ion-imprinted polymer (IIP) material containing multiple selective adsorption sites was synthesized using halloysite nanotubes, methyl acrylate, and ethylenediamine in the presence of a template ion [i.e. Cd (II) heavy metal]. The successful preparation of the Cd-IIP composition was confirmed by FT-IR, XRD, TEM, TGA, and elemental analysis. The polymers exhibited good adsorption of Cd (II) with a maximum adsorption capacity of 64.37 mg·g^-1. The imprinting factor (α) for Cd (II) was 2.62 and the selection factor (β) was 1.78, indicating a specific adsorption of Cd (II) ion. The selection coefficients of Cd-IIP for Cd (II)/Pb (II), Cd (II)/Cu (II), Cd (II)/Ni (II), Cd (II)/Cr (III), and Cd (II)/Na (I) also indicated an excellent selectivity of the hyperbranched polymers for Cd (II) in the presence of competitive ions. The removal efficiency remained more than 75% after five cycles of desorption/adsorption. We envision that the HNTs based Cd-IIP has promising applications in the removal of Cd (II) from wastewater.