Dual amperometric-potentiometric biosensor detection system for monitoring organophosphorus neurotoxins

A dual-transducer flow-injection biosensor detection system for monitoring organophosphorus (OP) neurotoxins is described. Such simultaneous use of different physical transducers in connection to the same (organophosphorous hydrolase (OPH)) enzyme enhances the information content and provides discrimination between various subclasses of OP compounds. While the potentiometric biosensor responds favorably to all OP compounds, reflecting the pH changes associated with the OPH activity, the amperometric device displays well-defined signals only towards OP substrates (pesticides) liberating the oxidizable p-nitrophenol product. The potentiometric detection has been accomplished with a silicon-based pH-sensitive electrolyte-insulator-semiconductor (EIS) transducer, operated in the constant-capacitance (ConCap) mode. Both transducers are prepared by a thin-film fabrication technology, and respond rapidly and independently to sudden changes in the level of the corresponding OP compound, with no apparent cross reactivity. Relevant experimental variables were evaluated and optimized. Such development holds great promise for field screening of OP neurotoxins in connection to various defense and environmental scenarios. The multiple-transduction concept could be extended for increasing the information content of other ‘class-enzyme’ biosensor systems.     

Environmental Monitoring System for Smart City Based on Secure Internet of Things (IoT) Architecture

Wireless Personal Communications - With increasing population, urbanization, energy, transportation, and agricultural developments, pollution is degrading the environment with ever-increasing pace....     

A mathematical model for beams on geosynthetic reinforced earth beds under strip loading

In this study, an attempt has been made to analyze a beam on geosynthetic reinforced earth beds subjected to strip loading. Geosynthetic layer has been assumed to have finite bending stiffness and therefore idealized as a beam. The foundation beam has been placed on compacted granular soil layer overlying the geosynthetic layer below which lies on the original weak/loose soil deposit. The upper dense and lower loose soil layers have been idealized as Winkler springs of different stiffnesses. Governing differential equations for the flexural response of the system have been derived and presented in non-dimensional form. These equations have been solved using appropriate boundary and continuity conditions. It was possible to obtain a closed form analytical solution for such a foundation system.     

Synthetic applications of rongalite: A green tool in the service of Diels–Alder chemistry and beyond

Rongalite or sodium hydroxymethanesulfinate dihydrate acts as a bleaching agent and it is used in printing and dying industry. Due to its ability to deliver SO₂ dianion, rongalite is useful to prepare sultines and sulfones. We have been exploiting its potential towards the construction of diverse polycylic frameworks. This account describes the utility of rongalite to expand the Diels–Alder chemistry via sultine or sulfone derivatives. In this context, rongalite played a critical role to increase the chemical space of unnatural amino acids, spirocycles, polycycles, sulfones and crown ethers.     

Relative Study of Luminescent Properties with Judd-Ofelt Characterization in Trivalent Europium Complexes Comprising ethyl-(4-fluorobenzoyl) Acetate

Five new europium(III) complexes Eu(p-EFBA)₃.(H₂O)₂ (C1), Eu(p-EFBA)₃.neo (C2), Eu(p-EFBA)₃.batho (C3), Eu(p-EFBA)₃.phen (C4), Eu(p-EFBA)₃.bipy (C5) have been synthesized by using ethyl-(4-fluorobenzoyl) acetate (p-EFBA) as β-ketoester ligand and neocuproine (neo), bathophenanthroline (batho), 1,10-phenanthroline (phen) and 2,2-bipyridyl (bipy) as ancillary ligands. The synthesized complexes C1-C5 were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (¹H-NMR), infrared (IR) spectroscopy, thermogravimetric analysis (TG/DTG), UV-visible and photoluminescence (PL) spectroscopy. The relative study of luminescence spectra of complexes with the previously reported complexes of isomeric ligand (ortho and meta substituted ligand) indicate the higher luminescence properties of complexes as an effect of fluorine position on β-ketoester ligand. The para substituted ligand shows a remarkable effect on quantum efficiencies and Judd-Ofelt intensity parameters (Ω_2, Ω₄) of the complexes. The higher value of intensity parameter Ω₂ associated with hypersensitive ⁵D₀ → ⁷F₂ transition of europium(III) ion revealing highly polarizable ligand field. The purposed energy transfer mechanism of complexes indicates the efficient energy transfer in complexes.     

Microwave-assisted regioselective addition of P(O)-H bonds to alkenes without added solvent or catalyst

The addition of P(O)-H bonds to alkenes has been accomplished using microwave irradiation in the absence of added solvent and catalyst. In addition to single addition reactions, tandem hydrophosphinylation reactions with alkynes afforded unsymmetrical species such as phosphine oxide-phosphinates. [reaction: see text]     

Design-of-Experiment Approach for the Development and Validation of a High-Performance Thin-Layer Chromatography Method for the Simultaneous Estimation of Berberine Chloride and Galangin in Tinospora cordifolia M. and Alpinia galanga L. and Their Herbal Formulations

JPC – Journal of Planar Chromatography – Modern TLC - In the present study, a design-of-experiment (DoE) approach Was used to determine optimized mobile-phase compositions for the...     

Spectroelectrochemistry and DFT analysis of a new {RuNO}n redox system with multifrequency EPR suggesting conformational isomerism in the {RuNO}7 state

The compound [Ru(NO)(bpym)(terpy)](PF6)3, bpym = 2,2'-bipyrimidine and terpy = 2,2':6',2"-terpyridine, with a {RuNO}6 configuration (angle Ru-N-O 175.2(4) degrees ) was obtained from the structurally characterized precursor [Ru(NO2)(bpym)(terpy)](PF6), which shows bpym-centered reduction and metal-centered oxidation, as evident from EPR spectroscopy. The relatively labile [Ru(NO)(bpym)(terpy)](3+), which forms a structurally characterized acetonitrile substitution product [Ru(CH3CN)(bpym)(terpy)](PF6)2 upon treatment with CH3OH/CH3CN, is electrochemically reduced in three one-electron steps of which the third, leading to neutral [Ru(NO)(bpym)(terpy)], involves electrode adsorption. The first-two reduction processes cause shifts of nu(NO) from 1957 via 1665 to 1388 cm(-1), implying a predominantly NO-centered electron addition. UV-vis-NIR Spectroscopy shows long-wavelength ligand-to-ligand charge transfer absorptions for [Ru(II)(NO(-I))(bpym)(terpy)]+ in the visible region, whereas the paramagnetic intermediate [Ru(NO)(bpym)(terpy)](2+) exhibits no distinct absorption maximum above 309 nm. EPR spectroscopy of the latter at 9.5, 95, and 190 GHz shows the typical invariant pattern of the {RuNO}7 configuration; however, the high-frequency measurements at 4 and 10 K reveal a splitting of the g1 and g2 components, which is tentatively attributed to conformers resulting from the bending of RuNO. DFT calculations support the assignments of oxidation states and the general interpretation of the electronic structure.     

Effect of silver nanoparticles on frequency and temperature-dependent electrical parameters of a discotic liquid crystalline material

The effect of silver nanoparticles (AgNPs) of diameters 6 and 100 nm on a discotic liquid crystalline material, namely 2,3,6,7,10,11-hexabutyloxytriphenylene (in short HAT4), has been observed in thermodynamic, electrical and optical texture studies. Silver nanoparticles (0.6 wt%) of diameter ~6 nm demonstrate a negligible (but ~100 nm shows appreciable) effect on the broad temperature range plastic columnar hexagonal (Col_hex) phase (~65.0°C) of pure HAT4. The dielectric studies have been carried out in the frequency range of 10 Hz–35 MHz under homeotropic anchoring conditions of the molecules. In the low frequency region of pure HAT4 and its AgNP composites, a relaxation mode has been observed. AgNPs of 6 nm elevate the value of dielectric permittivity of the plastic columnar hexagonal phase of pure HAT4. The dc conductivity of pure HAT4 and its AgNP composite (6 and 100 nm) material has been determined. The optical band gap for pure and AgNP composites of HAT4 has been determined by the ultraviolet-visible study. Due to insertion of AgNPs, the optical band gap of HAT4 has reduced.     

Reaction of Quinoline-5,8-Diones with Selected Charged Phosphorus Nucleophiles

Abstract

The redox reactivity of the two quinoline-5,8-dione derivatives—2-methyl-5,8-dioxo-5,8-dihydroquinoline-7-amine (2a) and N-(2-methyl-5,8-dioxo-5,8-dihydroquinolin-7-yl)acet-amide (2b)—has been demonstrated by their reaction with negatively charged three-coordinated phosphorus nucleophiles, such as R₂P-YM (1a–d, Y = O or lone pair; R = Ph, tBu, OCH₂CMe₂CH₂O, or EtO; M = Li or Na). 1a–d participated in single-electron transfer (SET) to 2a and 2b, generating the radical anions 3 and 4, respectively, together with short-lived phosphorus-centered radical intermediates of type R₂P(= Y)· (5). The radicals 5 dimerize to give R₂P(Y)–(Y)PR₂ (6). Both 3 and 4 are remarkably persistent with half-lives of more than 1 month in THF (tetrahydrofuran) at 300 K.