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71.
A simple spectrophotometric method is presented for the rapid determination of copper at a trace level using 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as a new spectrophotometric reagent. The method is based on the reaction of non-absorbent DMTD in a slightly acidic (0.002-0.014 mol dm(-3) sulfuric acid) aqueous solution with copper(II) to produce a highly absorbent greenish-yellow chelate product that has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.65 x 10(4) dm3 mol(-1) cm(-1) and 10 ng cm(-2) of CuII, respectively. Linear calibration graphs were obtained for 0.1-20 microg cm(-3) of CuII; the stoichiometric composition of the chelate is 1:2 (Cu:DMTD). A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere in the determination. The method was successfully used for the determination of copper in several Standard Reference Materials as well as in some environmental water samples, biological samples, soil samples and solutions containing both copper(I) and copper(II) and complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.5 microg cm(-1)). 相似文献
72.
A carbon paste electrode spiked with 1‐[4‐ferrocenyl ethynyl) phenyl]‐1‐ethanone (4FEPE) was constructed by incorporation of 4FEPE in graphite powder‐paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that this electrode can catalyze the oxidation of tryptophan (Trp) in aqueous buffered solution. It has been found that under optimum condition (pH 7.00), the oxidation of Trp at the surface of such an electrode occurs at a potential about 200 mV less positive than at an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and rate constant for the chemical reaction between Trp and redox sites in 4FEPE modified carbon paste electrode (4FEPEMCPE) were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of Trp showed a linear dependent on the Trp concentrations and linear calibration curves were obtained in the ranges of 6.00×10?6 M–3.35×10?3 M and 8.50×10?7 M–6.34×10?5 M of Trp concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined as 1.80×10?6 M and 5.60×10?7 M by CV and DPV methods. This method was also examined as a selective, simple and precise new method for voltammetric determination of tryptophan in real sample. 相似文献
73.
Ali A. Ensafi E. Heydari-Soureshjani M. Jafari-Asl B. Rezaei Jahan B. Ghasemi Elham Aghaee 《Analytica chimica acta》2015
A new electrochemical biosensor was developed to demonstrate the effect of Acridine Orange (AO) on DNA damage. Then, the biosensor was used to check the inhibitors effect of three flavonols antioxidants (myricetin, fisetin and kaempferol) on DNA damage. Acridine Orange (AO) was used as a damaging agent because it shows a high affinity to nucleic acid and stretch of the double helical structure of DNA. Decreasing on the oxidation signals of adenine and guanine (in the DNA) in the presence of AO were used as probes to study the antioxidants power, using DNA-modified screen printed graphene electrode (DNA/SPGE). The results of our study showed that the DNA-biosensor could be suitable biosensor to investigate the inhibitors ability of the flavonols antioxidants on the DNA damage. The linear dependency was detected in the two regions in the ranges of 1.0–15.0 and 15.0–500.0 pmol L−1. The detection limit was found 0.5 pmol L−1 and 0.6 pmol L−1 for guanine and adenine, respectively. To confirm the electrochemical results, Uv–Vis and fluorescence spectroscopic methods were used too. Finally molecular dynamic (MD) simulation was performed on the structure of DNA in a water box to study any interaction between the antioxidant, AO and DNA. 相似文献
74.
A Genosensor for Point Mutation Detection of P53 Gene PCR Product Using Magnetic Particles 下载免费PDF全文
Ezat Hamidi‐Asl Jahan Bakhsh Raoof Mohammad Saeid Hejazi Simin Sharifi Seyed Mahdi Golabi Ilaria Palchetti Marco Mascini 《Electroanalysis》2015,27(6):1378-1386
The development of an electrochemical genosensor involving DNA biotinylated capture probe immobilized on streptavidin coated paramagnetic beads and microfluidic based platform for the detection of P53 gene PCR product is reported. The novelty of this work is the combination of a sensitive electrochemical platform and a proper microfluidic system with a simple and effective enzyme signal amplification technology, ELISA, for detection of target DNA sequence and single nucleotide mutation in p53 tumor suppressor gene sequence. The biosensor has been applied to detect the PCR amplified samples and the results shows that it can discriminate successfully perfect matched DNA from mutant form. 相似文献
75.
Khan IA Khanam AJ Sheikh MS Kabir-ud-Din 《Journal of colloid and interface science》2011,359(2):467-473
Micellization of binary systems of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide) (16-4-16) and cationic/nonionic hydrotropes (aniline-hydrochloride, 2-methylanilinehydrochloride, 4-methylanilinehydrochloride, hydroxybenzene, 1,3-benzenediol, benzene-1,2,3-triol) have been studied using a conductometric technique. The critical micelle concentrations (cmc) for different mixing mole fractions at different temperatures have been calculated. To explain and compare the results, theoretical models of Clint, Rubingh and Motomura have been used to obtain the ideal cmc, mixed micelle composition, interaction parameters (β(m)), free energies of micellization, and activity coefficients. The mixtures show nonideal behavior and the interactions between the surfactants and the hydrotropes are synergistic in nature which is confirmed by high negative β(m) values and low values of the activity coefficients. Thermodynamic parameters were also obtained from the temperature dependence of the cmc values. 相似文献
76.
Asadollahi T Dadfarnia S Shabani AM Ghasemi JB Sarkhosh M 《Molecules (Basel, Switzerland)》2011,16(3):1928-1955
77.
78.
Malik Sajjad Mehmood Tariq Yasin Muhammad Shah Jahan Benjamin Michael Walters Manzoor Ahmad Masroor Ikram 《Applied magnetic resonance》2013,44(4):531-542
Thermal effects on ultra-high-molecular-weight polyethylene (UHMWPE) residual radicals during the vitamin E diffusion process were studied in detail. Electron paramagnetic resonance (EPR) technique showed a significant reduction in concentrations of radiation-induced primary (alkyl (–CH2– ?CH–CH2–), allyl (–CH2–?CH=CH–CH–CH2–) and polyenyl (–?CH–[CH=CH–] m –) with m > 3) radicals for both control and vitamin E-doped samples. The concentrations of radiation-induced primary radicals (RIPRs) were found to decrease proportionally with the heat/diffusion time. While the EPR spectra of the control samples showed only polyethylene (PE) radicals, the spectra of vitamin E-doped samples were found to exhibit vitamin E radicals in addition to PE radicals. Of particular interest, the heat involved during vitamin E diffusion plays a significant role in reducing the radiation-induced primary radicals of UHMWPE. For 120 min of heat/diffusion time, the available quantity of primary radicals in control samples were found to be ~7.5 % of initial radicals. The leftover amounts of these primary radicals for vitamin E-doped samples were approximately ~10.0 %. In addition to this, EPR power saturation techniques were also used to assess the effects of initial heat/diffusion treatment on the oxygen-induced residual radicals (OIRRs): R1 (–?CH–[CH=CH–] m –) with m > 3 and R2 (?OCH–[CH=CH–] m –) with m = 2 or 3. It was found that the concentration of OIRRs also decreases proportionally with initial heat/diffusion time. The remaining amount of OIRRs relative to leftover RIPRs after heat/diffusion was found to be approximately 4.0 % in controls and was still found to be 10.0 % in vitamin E-doped UHMWPE. This may indicate that vitamin E slows down the oxidation processes, which may contribute to the strong oxidation resistance of vitamin E-doped UHMWPE. 相似文献
79.
Kun Wang Chengcheng Zhu Yafeng He Zhenqin Zhang Wen Zhou Nafees Muhammad Yan Guo Xiaoyong Wang Zijian Guo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(14):4686-4691
Cancer cells usually adapt metabolic phenotypes to chemotherapeutics. A defensive strategy against this flexibility is to modulate signaling pathways relevant to cancer bioenergetics. A triphenylphosphonium‐modified terpyridine platinum(II) complex (TTP) was designed to inhibit thioredoxin reductase (TrxR) and multiple metabolisms of cancer cells. TTP exhibited enhanced cytotoxicity against cisplatin‐insensitive human ovarian cancer cells in a caspase‐3‐independent manner and showed preferential inhibition to mitochondrial TrxR. The morphology and function of mitochondria were severely damaged, and the levels of mitochondrial and cellular reactive oxygen species were decreased. As a result, TTP exerted strong inhibition to both mitochondrial and glycolytic bioenergetics, thus inducing cancer cells to enter a hypometabolic state. 相似文献
80.
Eskandarpour Maryam Jamshidi Parastoo Moghaddam Mohammad Reza Ghasmei Jahan B. Shemirani Farzaneh 《Research on Chemical Intermediates》2019,45(5):3141-3153
Research on Chemical Intermediates - In this work, a highly selective method is presented for the preconcentration of cadmium. The developed magnetic solid-phase extraction is based on the... 相似文献