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5-Amino-1,3,4-thiadiazole-2-thiol was used to synthesize a novel fluorescent functionalizing group on a Fe 3 O 4 @SiO 2 magnetic nanocomposite surface for detection of heavy metal ions in water samples. The prepared probe was characterized by using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and a vibrating sample magnetometer. Among various tested ions, the new nanocomposite responded to Hg 2+ ions with an intense fluorescence “turn-off”. The limit of detection of the probe shows that it is sensitive to the minimum Hg 2+ concentration of 48.7 nM. Theoretical calculations were done for estimating binding energies of the three possible bonding modes.
In this work, a new method based on homogeneous liquid-phase microextraction was developed for the determination of methadone and tramadol. Dipropylamine was used as extraction solvent with switchable hydrophilicity that can be miscible/ immiscible upon the addition or removal of CO2 as a reagent. The effects of operational parameters of the extraction such as volume of acceptor phase, volume of donor phase, pH of donor phase, and ionic strength of solution were investigated. Under optimal conditions, the preconcentration factors, the detection limits and the linearity of the method were achieved in the ranges of 135–138, 1.2 and 4–1000 μg L−1, respectively. Finally, the proposed method has been successfully applied to the analysis of methadone and tramadol in urine samples. In urine sample, the preconcentration factors were 118 and 122 for methadone and tramadol, respectively. Additionally, calibration curves were found to be linear in the concentration range of 8–1000 μg L−1 with the r2 values better than 0.998. In addition, limits of detection and quantification were 2.4 and 8 μg L−1, respectively, for both analytes.
In this article, a simple and efficient kind of homogeneous liquid-liquid microextraction based on an acid–base reaction using switchable-hydrophilicity solvents was proposed for the quantification of nitrazepam. Analyte is extracted into the N,N‑dipropylamine as an extraction solvent with the assistance of HCl and NaOH as pH adjustment reagents. Initially, a switchable solvent is added to the aqueous sample spiked with the analyte, which leads to the formation of a two phase mixture. Then, HCl is added drop by drop, until a clear and monophasic solution is obtained because of the switching of N,N‑dipropylamine into the hydrophilic form. Afterward, the separation of phases is achieved by addition of NaOH which results in switching back N,N‑dipropylamine to its primary hydrophobic form. Finally, after the evaporation of solvent, the extracted nitrazepam was analyzed by voltammetric methods. The influences of experimental factors on the extraction efficiency (organic solvent volume, pH of sample solution, extraction time, and salt addition) were investigated and optimized. Two linear ranges of 0.03–20 ng mL−1 and 20–450 ng mL−1 with the correlation coefficients of 0.996 and 0.998 were obtained from voltammetry measurements. The Limits of detection and quantification were obtained 9 ng L−1 and 0.03 ng mL−1 respectively. Also, the RSD% value of the method was calculated to be 7.4%. Finally, the proposed method was successfully applied for the determination of nitrazepam in human urine samples.
Glycogen synthase kinase-3 (GSK3) is a potential therapeutic target in bipolar disorder. Here, a three-dimensional quantitative structure–activity relationship (3D-QSAR) namely CoMFA, CoMFA-RF (region focusing), and CoMSIA has been carried out on a series (44 compounds) of GSK3 inhibitors on maleimide-based. The data set was divided into training set (32 compounds) and test set (12 compounds) using Kennard and Stone algorithm. An alignment rule for the training set was defined on the basis of common substructure-based alignment. The all-orientation search (AOS) was used to achieve the best orientation and minimize the effect of initial orientation of the structures. The statistical parameters from the models (CoMFA: q2 = 0.56, , CoMFA-RF: q2 = 0.70, , and CoMSIA: q2 = 0.60, ) indicate that the data are well fitted and have high predictive ability. Molecular docking was employed to explore the binding mode between these compounds and the receptor, as well as help understand the structure–activity relationship revealed by CoMFA and CoMSIA. The computer-aided design of new compounds as potential GSK-3 inhibitors with the application of defined structural alerts was presented
Pathogenic Gram-negative bacteria are responsible for nearly half of the serious human infections. Hologram quantitative structure–activity relationships (HQSAR), comparative molecular field analysis (CoMFA), and comparative molecular similarity index analysis (CoMSIA) were implemented on a group of 32 of potent Gram-negative LpxC inhibitors. The most effective HQSAR model was obtained using atoms, bonds, donor, and acceptor as fragment distinction. The cross-validated correlation coefficient (q2), non-cross-validated correlation coefficient (r2), and predictive correlation coefficient (r2Pred) for test set of HQSAR model were 0.937, 0.993, and 0.892, respectively. The generated models were found to be statistically significant as the CoMFA model had (r2¼0.967, q2¼0.804, r2Pred¼0.827); the CoMSIA model had (r2¼0.963, q2¼0.752, r2Pred¼0.857). Molecular docking was employed to validate the results of the HQSAR, CoMFA, and CoMSIA models. Based on the obtained information, six new LpxC inhibitors have been designed.
روش ساده، سریع و ارزان میکرواستخراج مایع-مایع پخشی براساس جامدکردن قطره شناور با استفاده از سوانگاری مایع با عملکرد بالا (HPLC) برای استخراج و تعیین مقادیر آتورواستاتین در نمونههای قرص بهکار برده شده است. اثر عاملهایی مانند حجم حلال استخراجکننده، حجم حلال پخش کننده و pH با استفاده از طراحی آزمایش بهینه شدند. تحت شرایط بهینه، منحنی واسنجی با دامنه خطی ا تا 200 میکروگرم بر لیتر با حد تشخیص 3/0 میکروگرم بر لیتر بهدست آمد. روش بهینه شده دقت و انحراف استاندارد نسبی خوبی را با مقدار 2/2 % نشان داد. توانایی روش معرفیشده برای اندازهگیری آتورواستاتین در نمونههای قرص نیز مورد آزمون قرارگرفت. نتایج این کار نشان داد که روش معرفیشده کارایی استخراج بالا و حد تشخیص پایین دارد. مهمترین مزیت این روش استفاده از حجم بالای نمونه و حذف حلالهای آلی سمی است.
5-Amino-1,3,4-thiadiazole-2-thiol was used to synthesize a novel fluorescent functionalizing group on a Fe3O4@SiO2 magnetic nanocomposite surface for detection of heavy metal ions in water samples. The prepared probe was characterized by using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and a vibrating sample magnetometer. Among various tested ions, the new nanocomposite responded to Hg2+ ions with an intense fluorescence “turn-off”. The limit of detection of the probe shows that it is sensitive to the minimum Hg2+ concentration of 48.7 nM. Theoretical calculations were done for estimating binding energies of the three possible bonding modes and the visualized molecular orbitals were presented.
Polychlorinated biphenyls (PCBs) are a class of synthetic organic compounds that are hazardous due to their chemical and thermal stability, hydrophobicity and toxic properties [1-2]. PCBs often exist at trace levels of concentration in the environment, so an effective pretreatment step is necessary for their preconcentration before quantification. In this study, a new method was successfully developed for the simultaneous determination of seven polychlorinated biphenyls in aqueous samples with switchable hydrophilicity solvent based liquid phase microextraction coupled to GC-MS detection. Triethylamine (TEA) was used as extraction solvent with switchable polarity, which can be miscible/immiscible upon the changes of pH of sample solution. The factors influencing the extraction efficiency, including type and volume of extraction solvent, pH and volume of aqueous sample, extraction time, and salt addition were investigated and optimized. Under the optimized conditions, good linearity (0.5-150 μg/L) and limits of detection (0.15 μg/L) were obtained for the PCBs by the proposed method. Also, the relative standard deviations (RSDs) were calculated between 5.2 and 6.4 %. In addition, enrichment factors (EFs) and extraction recoveries (ERs) were obtained in the ranges of 30.46-32.10 and 76.15-80.25 respectively. Finally, the proposed method was successfully applied for the analysis of PCBs in various water samples with excellent relative recoveries (RRs, 96.30-102.60).