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991.
Nidhi Rani Gupta S. K. Ashok Kumar Susheel K. Mittal Prabhpreet Singh Subodh Kumar 《Journal of Analytical Chemistry》2017,72(2):191-202
New poly(vinylchloride) (PVC) based liquid membrane sensors are reported containing neutral macrocyclic carrier as potential ionophores for sensing silver ions. Three macrocycles (L1, L2 and L3) possessing two thioether, two amide and one secondary amine unit have been used in new PVC membrane-based sensor. At wide pH range of 4.5 to 8.0, these sensors exhibit linear responses in the concentration range of 1 × 10–4 to 0.1 M and detection limit 6 × 10–5 M for L1 and 1 × 10–4 M for L2 and L3 respectively with pseudo-Nernstian slopes between 43?46 mV/decade for all the three sensors. These sensors have short response time (<15 s) and long life time as these sensors do not show any considerable divergence in their performance over a period of four months. These sensors exhibit good selectivity for Ag+ over wide variety of interfering ions like alkali, alkaline earth, transition and some heavy metal ions. These proposed sensors could be used successfully as indicator electrodes in the potentiometric determination of Ag+ ions and also to determine anions like Cl–, Br–, I–, S2–, SCN– and CN–. Potentiometric titrations for halide ions in a mixture using these sensors and new titration method for the determination of detection limits are reported. 相似文献
992.
A carpet-like nanostructure of polyaniline (PANI) nanothin film functionalized with poly(ethyleneimine), PEI, was used as a miniature chemiresistor sensor for detection of CO2 at room temperature. Good sensing performance was observed upon exposing the PEI–PANI device to 50–5000 ppm CO2 in presence of humidity with negligible interference from ammonia, carbon monoxide, methane and nitrogen dioxide. The sensing mechanism relied on acid–base reaction, CO2 dissolution and amine-catalyzed hydration that yielded carbamates and carbonic acid for a subsequent pH detection. The sensing device showed reliable results in detecting an unknown concentration of CO2 in air. 相似文献
993.
Synthesis of Amphiphilic RuII Heteroleptic Complexes Based on Benzo[1,2‐b:4,5‐b′]dithiophene: Relevance of the Half‐Sandwich Complex Intermediate and Solvent Compatibility 下载免费PDF全文
Dr. Maxence Urbani María Medel Dr. Sangeeta Amit Kumar Dr. Mine Ince Prof. Ashok N. Bhaskarwar Dr. David González‐Rodríguez Michael Grätzel Prof. Mohammad Khaja Nazeeruddin Prof. Tomás Torres 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16252-16265
The detailed synthesis and characterization of four ruthenium(II) complexes [RuLL′(NCS)2] is reported, in which L represents a 2,2′‐bipyridine ligand functionalized at the 4,4′ positions with benzo[1,2‐b:4,5‐b′]dithiophene derivatives (BDT) and L′ is 2,2′‐bipyridine‐4,4′‐dicarboxylic acid unit (dcbpy) (NCS=isothiocyanate). The reaction conditions were adapted and optimized for the preparation of these amphiphilic complexes with a strong lipophilic character. The photovoltaic performances of these complexes were tested in TiO2 dye‐sensitized solar cell (DSSC) achieving efficiencies in the range of 3–4.5 % under simulated one sun illumination (AM1.5G). 相似文献
994.
Double Strain‐Promoted Macrocyclization for the Rapid Selection of Cell‐Active Stapled Peptides 下载免费PDF全文
Dr. Maxim Rossmann Dr. Ban Xiong Tan Dr. Peterson de Andrade Dr. Yaw Sing Tan Dr. Chandra Verma Dr. Grahame J. McKenzie Prof. Ashok R. Venkitaraman Dr. Marko Hyvönen Prof. David R. Spring 《Angewandte Chemie (International ed. in English)》2015,54(51):15410-15413
Peptide stapling is a method for designing macrocyclic alpha‐helical inhibitors of protein–protein interactions. However, obtaining a cell‐active inhibitor can require significant optimization. We report a novel stapling technique based on a double strain‐promoted azide–alkyne reaction, and exploit its biocompatibility to accelerate the discovery of cell‐active stapled peptides. As a proof of concept, MDM2‐binding peptides were stapled in parallel, directly in cell culture medium in 96‐well plates, and simultaneously evaluated in a p53 reporter assay. This in situ stapling/screening process gave an optimal candidate that showed improved proteolytic stability and nanomolar binding to MDM2 in subsequent biophysical assays. α‐Helicity was confirmed by a crystal structure of the MDM2‐peptide complex. This work introduces in situ stapling as a versatile biocompatible technique with many other potential high‐throughput biological applications. 相似文献
995.
Development of a fabric phase sorptive extraction with high‐performance liquid chromatography and ultraviolet detection method for the analysis of alkyl phenols in environmental samples 下载免费PDF全文
Rajesh Kumar Gaurav Kenneth G. Furton Ashok Kumar Malik 《Journal of separation science》2015,38(18):3228-3238
A novel analytical method has been developed and validated for the quantification of alkyl phenols in aqueous and soil samples. Fabric phase sorptive extraction, a new sorptive microextraction technique, has been employed for the preconcentration of some endocrine‐disruptor alkylphenol molecules, namely, 4‐tert‐butylphenol, 4‐sec‐butylphenol, 4‐tert‐amylphenol, and 4‐cumylphenol, followed by high‐performance liquid chromatography with ultraviolet detection. Various parameters influencing the fabric phase sorptive extraction performance, namely, extraction time, eluting solvent, elution time and pH of the sample matrix, were optimized. The chromatographic separation was carried out with a mobile phase of acetonitrile/water (60:40 v/v) at an isocratic flow rate of 1.0 mL/min using a reversed‐phase C18 column at λmax 225 nm. The calibration curves of target analytes were prepared in the concentration range 5–500 ng/mL with good coefficient of determination values (R2 > 0.992). Extraction efficiency values were 74.0, 75.6, 78.0, and 78.3 for 4‐tert‐butylphenol, 4‐sec‐butylphenol, 4‐tert‐amylphenol, and 4‐cumylphenol, respectively. The limits of detection range from 0.161 to 0.192 ng/mL. Subsequently, the new fabric phase sorptive extraction with high‐performance liquid chromatography and ultraviolet detection was successfully applied for the recovery of alkyl phenols from spiked ground water, river water, and treated water from a sewage treatment plant, and soil and sludge samples. 相似文献
996.
Esther Alza Luca Laraia Brett M. Ibbeson Súil Collins Warren R. J. D. Galloway Jamie E. Stokes Ashok R. Venkitaraman David R. Spring 《Chemical science》2015,6(1):390-396
The synthesis of a previously undescribed sp3-rich 6-5-5-6 tetracyclic ring scaffold using a palladium catalysed domino Heck–Suzuki reaction is reported. This reaction is high-yielding, selective for the domino process over the direct Suzuki reaction and tolerant towards a variety of boronic acids. The novel scaffold can also be accessed via domino Heck–Stille and radical cyclisations. Compounds based around this scaffold were found to be effective antimitotic agents in a human cancer cell line. Detailed phenotypic profiling showed that the compounds affected the congression of chromosomes to give mitotic arrest and apoptotic cell death. Thus, a novel structural class of antimitotic agents that does not disrupt the tubulin network has been identified. 相似文献
997.
Rajashri R. Naik Ashok K. Shakya Benedetta Ferri Ghaleb A. Oriquat Luisa Pistelli Nawfal A. M. Numan 《Molecules (Basel, Switzerland)》2021,26(18)
The present paper reports the GC-HS-SPME analysis of volatile emission and GC-MS analysis of chemical composition of essential oil of R. coriaria fruits of eight different samples of R. coriaria L. fruits (“sumac” folk name), collected from Jordanian agricultural field and the local market. The analyses show an important variability among the Sumac samples probably due to the origin, cultivation, harvesting period, drying, and conservation of the plant material. The main class of component present in all samples was monoterpenes (43.1 to 72.9%), except for one sample which evidenced a high percentage of sesquiterpene hydrocarbons (38.5%). The oxygenated monoterpenes provided a contribution to total class of monoterpenes ranging from 10.1 to 24.3%. A few samples were rich in monoterpene hydrocarbons. Regarding the single components present in all the volatile emissions, β-caryophyllene was the main compound in most of the analyzed samples, varying from 34.6% to 7.9%. Only two samples were characterized by α-pinene as the main constituent (42.2 and 40.8% respectively). Essential oils were collected using hydro-distillation method. Furfural was the main constituent in almost all the analyzed EOs (4.9 to 48.1%), except in one of them, where β-caryophyllene was the most abundant one. β-caryophyllene ranged from 1.2 to 10.6%. Oxygenated monoterpenes like carvone and carvacrol ranged from 3.2–9.1% and 1.0–7.7% respectively. Cembrene was present in good amount in EO samples EO-2 to EO-8. The antioxidant capacities of the fruit essential oils from R. coriaria were assessed using spectrophotometry to measure free radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and inhibition of β-carotene bleaching (BCB). The essential oils from the fruits of the different samples of R. coriaria exhibited the MIC value ranging from 32.8 to 131.25 µg/mL against S. aureus ATCC 6538 and 131.25 to 262.5 µg/mL against E. coli ATCC 8739. The MIC values of ciprofloxacin were 0.59 and 2.34 µg/mL against S. aureus ATCC 6538 and E. coli ATCC 8739, respectively. 相似文献
998.
Ashok Razdan 《Pramana》2000,54(6):871-878
We compare the anharmonic Lamb Mossbauer factor and the q-Lamb Mossbauer factor by studying the anharmonicity observed in the f-factor data of Nb3Sn. We also show that this anharmonicity does not arise due to the presence of potential. 相似文献
999.
1000.