Synthesis of lariat ether carboxylic acids based on dibenzo‐16‐crown‐5

Synthetic routes to forty‐seven dibenzo‐16‐crown‐5 compounds with pendant carboxylic acid groups are reported. When taken together with previously described lariat ether carboxylic acids, these new compounds provide several series with systematic structural variations including changes in the identity and attachment site(s) of one or more lipophilic groups and the length of the spacer that connects the carboxylic acid group to the polyether framework.     

Enzyme-modulated cleavage of dsDNA for studying interfacial biomolecular interactions.

This work describes the chemistry and methodology for constructing multilayers of bis-biotinylated dsDNA on metal substrates after enzyme cleavage and demonstrates its use for amplified microgravimetric and impedimetric analyses of anticancer drug, cisplatin. Specific chemical modification of dsDNA prior to immobilization was achieved via a bisulfite-catalyzed transamination of cytosine after endonuclease cleavage of plasmid DNA. The specificity of the reaction of cytosine residues at ss- versus dsDNA loci after endonuclease cleavage was characterized using circular dichroism, mass spectrometry, and absorption spectrophotometry. The biotinylated dsDNA consisting of 2961 base pairs was then used as a ligand at avidin-modified gold electrodes. Ac impedance spectroscopy and quartz crystal microbalance measurements clearly showed that the response to cisplatin increased linearly with target concentrations. The impedance spectroscopy resulted in a detection limit of 1 nM and a surface density of 4.8 x 10(13) molecules/0.1 cm(2). The immobilization of dsDNA on surfaces is a significant improvement over existing approaches in that it enables the attachment of long pieces of unmodified double-stranded DNA via a simple biotinylation step. The immobilization technique provides a generic approach for dsDNA-based sensor development and for monitoring DNA-analyte interactions.     

Polyphenolics with Strong Antioxidant Activity from Acacia nilotica Ameliorate Some Biochemical Signs of Arsenic-Induced Neurotoxicity and Oxidative Stress in Mice

Neurotoxicity is a serious health problem of patients chronically exposed to arsenic. There is no specific treatment of this problem. Oxidative stress has been implicated in the pathological process of neurotoxicity. Polyphenolics have proven antioxidant activity, thereby offering protection against oxidative stress. In this study, we have isolated the polyphenolics from Acacia nilotica and investigated its effect against arsenic-induced neurotoxicity and oxidative stress in mice. Acacia nilotica polyphenolics prepared from column chromatography of the crude methanol extract using diaion resin contained a phenolic content of 452.185 ± 7.879 mg gallic acid equivalent/gm of sample and flavonoid content of 200.075 ± 0.755 mg catechin equivalent/gm of sample. The polyphenolics exhibited potent antioxidant activity with respect to free radical scavenging ability, total antioxidant activity and inhibition of lipid peroxidation. Administration of arsenic in mice showed a reduction of acetylcholinesterase activity in the brain which was counteracted by Acacia nilotica polyphenolics. Similarly, elevation of lipid peroxidation and depletion of glutathione in the brain of mice was effectively restored to normal level by Acacia nilotica polyphenolics. Gallic acid methyl ester, catechin and catechin-7-gallate were identified in the polyphenolics as the major active compounds. These results suggest that Acacia nilotica polyphenolics due to its strong antioxidant potential might be effective in the management of arsenic induced neurotoxicity.     

Metal-free multicomponent synthesis and in vitro antioxidant activity of indolylpyrazolopyrimidines

Multisubstituted indolylpyrazolopyrimidines were synthesized in good yields with base promoted one-pot multicomponent system from aldehyde, ketone, and indolylpyrazolamine. Milder and cost-effective conditions are the highlights of the present protocol. Among the synthesized compounds ( 4a-j ) 4b , 4c , 4e , and 4f have shown significant better in vitro antioxidant activity compared to standard ascorbic acid.     

Synthesis of macrocyclic polyethers with partially fluorinated side arms

Different types of macrocyclic polyethers with partially fluorinated side arms are prepared. These new macrocyclic ligands are based on sym‐dibenzo‐16‐crown‐5 and sym‐dicyclohexano‐16‐crown‐5 scaffolds.     

Detection and classification of organophosphate nerve agent simulants using support vector machines with multiarray sensors

The need for rapid and accurate detection systems is expanding and the utilization of cross-reactive sensor arrays to detect chemical warfare agents in conjunction with novel computational techniques may prove to be a potential solution to this challenge. We have investigated the detection, prediction, and classification of various organophosphate (OP) nerve agent simulants using sensor arrays with a novel learning scheme known as support vector machines (SVMs). The OPs tested include parathion, malathion, dichlorvos, trichlorfon, paraoxon, and diazinon. A new data reduction software program was written in MATLAB V. 6.1 to extract steady-state and kinetic data from the sensor arrays. The program also creates training sets by mixing and randomly sorting any combination of data categories into both positive and negative cases. The resulting signals were fed into SVM software for "pairwise" and "one" vs all classification. Experimental results for this new paradigm show a significant increase in classification accuracy when compared to artificial neural networks (ANNs). Three kernels, the S2000, the polynomial, and the Gaussian radial basis function (RBF), were tested and compared to the ANN. The following measures of performance were considered in the pairwise classification: receiver operating curve (ROC) Az indices, specificities, and positive predictive values (PPVs). The ROC Az) values, specifities, and PPVs increases ranged from 5% to 25%, 108% to 204%, and 13% to 54%, respectively, in all OP pairs studied when compared to the ANN baseline. Dichlorvos, trichlorfon, and paraoxon were perfectly predicted. Positive prediction for malathion was 95%.     

Oxovanadium(IV) complexes of bromo-and methoxy substituted N1,N4-diarylidene-S-methylthiosemicarbazones

Four new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations. The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis, conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g_‖ < g_⊥ < g_e = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The EPR spectra recorded from solution forms almost have isotropic character.     

Investigation of the thermoelectrical properties of the Sn91.2−x–Zn8.8–Agx alloys

Journal of Thermal Analysis and Calorimetry - Sn91.2?x–Zn8.8–Agx alloys (x&nbsp;=&nbsp;0.15–10.0&nbsp;wt%) were directionally solidified upwards at a constant G...     

Theoretical calculations on structural and electronic properties of BGaAsBi alloys

The structural and electronic properties of cubic B _x Ga_1?x As_1?y Bi _y alloys with bismuth (Bi) concentration of 0.0625, 0.125, 0.1875 and 0.25 are studied with various boron (B) compositions by means of density functional theory (DFT) within the Wu-Cohen (WC) exchange correlation potential based on generalized gradient approximation (GGA). For all studied alloy structures, we have implemented geometric optimization before the volume optimization calculations. The obtained equilibrium lattice constants and band gap of studied quaternary alloys are investigated for the first time in literature. While the lattice constant behavior changes linearly with boron concentration, increasing small amount of bismuth concentration alter the lattice constant nonlinearly. The present calculation shows that the band gap decreases with increasing bismuth concentration and direct band gap semiconductor alloy became an indirect band gap with increasing boron concentration. From the band offset calculation we have shown that increasing B and Bi concentration in host GaAs reduced the valance band offset in a heterostructure formed by GaAs and studied alloys.     

Generalized qd algorithm and Markov–Bernstein inequalities for Jacobi weight

The Markov–Bernstein inequalities for the Jacobi measure remained to be studied in detail. Indeed the tools used for obtaining lower and upper bounds of the constant which appear in these inequalities, did not work, since it is linked with the smallest eigenvalue of a five diagonal positive definite symmetric matrix. The aim of this paper is to generalize the qd algorithm for positive definite symmetric band matrices and to give the mean to expand the determinant of a five diagonal symmetric matrix. After that these new tools are applied to the problem to produce effective lower and upper bounds of the Markov–Bernstein constant in the Jacobi case. In the last part we com pare, in the particular case of the Gegenbauer measure, the lower and upper bounds which can be deduced from this paper, with those given in Draux and Elhami (Comput J Appl Math 106:203–243, 1999) and Draux (Numer Algor 24:31–58, 2000).