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PubMed2006

Preparation and thermal studies on tetranitrodibenzo tetraazapentalene (TACOT): a thermally stable high explosive.

Thermally stable high explosive, tetranitro-2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene (TACOT) was synthesized and characterized during this work. Thermo analytical techniques (TG and DSC) were applied to study the thermal decomposition behaviour of TACOT in comparison with benchmark thermally stable high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Kinetic parameters such as reaction order, activation energy and pre-exponential factors were computed from the thermal data. The activation energy for TACOT (292 kJ/mol) was found 1.5 times to that of TATB (200 kJ/mol), which can account for its higher thermal stability and can be attributed to pentalene moiety in the former.

Aza Compounds↗
PubMed2001

Degradation of imidacloprid in water by photo-Fenton and TiO2 photocatalysis at a solar pilot plant: a comparative study.

The technical feasibility, mechanisms, and performance of degradation of aqueous imidacloprid have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (<2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with photo-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal anytoxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detected which were always the same. At the end of both processes low concentration (<0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around 1 mg/L of formate in the case of photo-Fenton.

Ferric Compounds↗
PubMed2005

Light-controlled molecular switches modulate nanocrystal fluorescence.

Spiropyran dyes were attached to fluorescent core-shell CdSe/ZnS nanocrystals via thiol-containing linkers. Photoisomerization of the dye to its merocyanine form by UV irradiation caused a dramatic loss in the intrinsic nanoparticle fluorescence, which was regained upon reversing the isomerization with visible light. The fluorescence quenching efficiency increased with increasing spectral overlap of fluorescence emission and merocyanine adsorption bands, consistent with FRET as the quenching mechanism. Typically, complete quenching required at least 80 bound dye molecules per particle.

Benzopyrans↗
PubMed1998

Arylaminobenzoate block of the cardiac cyclic AMP-dependent chloride current.

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel has been identified in the cardiac muscle of a number of mammalian species, including humans. The goal of this study was to begin quantifying the structural requirements necessary for arylaminobenzoate block of the CFTR channel. The cardiac cAMP-dependent Cl- current (ICl) was measured using the whole-cell arrangement of the patch-clamp technique in guinea pig ventricular myocytes during stimulation of protein kinase A with forskolin. At drug concentrations below the IC50 value for channel block, reduction of ICl by the arylaminobenzoates occurred in a strongly voltage-dependent manner with preferential inhibition of the inward currents. At higher drug concentrations, block of both the inward and outward ICl was observed. Increasing the length of the carbon chain between the benzoate and phenyl rings of the arylaminobenzoates resulted in a marked increase in drug block of the channel, with IC50 values of 47, 17, and 4 microM for 2-benzylamino-5-nitro-benzoic acid, 5-nitro-2-(2-phenylethylamino)-benzoic acid, and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), respectively. Increasing the carbon chain length further with the compound 5-nitro-2-(4-phenylbutylamino)-benzoic acid, caused no additional increase in the potency of drug block (IC50 = 4 microM). Inhibition of ICl by the arylaminobenzoates was modulated by the pH of the external solution; increasing the pH from 7.4 to 10.0 greatly weakened NPPB block, whereas decreasing the pH to 6.4 enhanced block. In addition, block of ICl was observed during intracellular dialysis of NPPB, and this action was not affected by raising the external pH.

Animals↗
PubMedDate not supplied

[Computer-aided prediction of the mutagenic activity substituted polycyclic compounds].

The relationship between mutagenic activity and chemical structure was studied for 54 polycyclic compounds using two approaches: multiple linear regression analysis and artificial neural networks. Structural fragments, quantum chemical indices, and hydrophobicity (octanol-water partition coefficient) were used as descriptors (properties of the molecules introduced in the model). Both linear regression equations and nonlinear relationships obtained with the help of a neural network were shown to accurately predict mutagenic activity for the compounds structurally similar to those in the training sample. The introduction of experimentally selected descriptors is substantiated to verify the proposed mechanism of related compounds mutagenic activity.

Heterocyclic Compounds, 3-Ring↗
PubMed1988

Oxidative detection of coulometrically reduced organonitro pesticides in reversed-phase high-performance liquid chromatography.

A high-performance liquid chromatographic system is presented for determination of organonitro pesticides, metabolites and industrial chemicals having a variety of chemical structures. The compounds are chromatographed on a C8 column with an acetonitrile-aqueous ammonium monochloroacetate gradient. The chromatographic responses of the compounds are monitored indirectly by oxidative detection of the coulometrically reduced organonitro functionality by means of a porousgraphite detector. Three nitrophenols (2,4-dinitrophenol, 4,6-dinitro-o-cresol and dinoseb), a dinitrophenyl aliphatic ester (binapacryl) and a nitroaniline (dicloran) were detected at low nanogram levels (3-10 ng for 50% recorder full-scale deflection). This technique overcomes the problems of high background currents and oxygen interference, observed in the direct reductive detection of organonitro compounds.

Chromatography, High Pressure Liquid↗
PubMed1996

Antianginal effects of FR144420, a novel slow nitric oxide-releasing agent.

The aim of this study was to compare the antianginal effects of two compounds that release nitric oxide (NO) spontaneously, i.e. (+/-)-N-[(E)-4-ethyl-3-[(Z-hydroxyimino]-5-nitro-3-hexenyl] -3-pyridinecarboxamide (FR144420) and (+/-)-(E)-ethyl-2-[(E)-hydroxyimino] -5-nitro-3-hexenamide (FK409), in two different rat models of coronary vasospasm. In the rat methacholine-induced coronary vasospasm model, FR144420 suppressed the elevation of the ST segment dose dependently and significantly at 1.0 mg/kg, i.d. 185 min after its administration. FK409 suppressed the ST elevation only 5 min after its administration at 1.0 mg/kg, i.d. FR144420 and FK409 significantly decreased mean blood pressure at all doses tested only 5 min after their intraduodenal administration, but did not change heart rate at any time. Although the suppression of the ST elevation by FK409 had the same duration as its hypotensive effect, the FR144420-induced suppression of the ST elevation lasted longer than its hypotensive effect. In the rat vasopressin-induced coronary vasospasm model, FR144420 (32 mg/kg) significantly inhibited the depression of the ST segment both 60 min and 120 min after oral administration, whereas FK409 (32 mg/kg) significantly inhibited this ST depression only 60 min after oral administration. These data suggest that FR144420 inhibits coronary vasospasm for longer than FK409 does and particularly shows more prolonged antianginal effects than hypotensive effects in the methacholine-induced coronary vasospasm model. Thus FR144420 is expected to be a useful NO releaser for investigating the in vivo actions of NO.

Animals↗
PubMed1995

A new nitric oxide (NO) releaser: spontaneous NO release from FK409.

The remarkable vasorelaxant and anti-platelet effects of FK409 have been reported to be due to nitric oxide (NO) release. The purpose of the present study is to investigate the spontaneous NO-releasing pathway of FK409 in aqueous solutions. 1H-NMR spectra of FK409 suggested that the compound underwent a time-dependent elimination of the hydrogen atom at alpha-position of the nitro moiety (at the 5-position) in weakly alkaline solutions. In addition, the degradation of FK409 monitored by HPLC showed a pH-dependency accelerating with an increase of pH. These results revealed that the first step in the degradation of FK409 might be the hydroxyl ion-dependent subtraction of the hydrogen atom at the 5-position. On the other hand, NO release from FK409 also exhibited a pH-dependency, and the velocity of NO liberation was markedly enhanced above pH 6. Furthermore, a linear relationship between the rate of FK409 degradation and that of NO formation was observed, indicating that the rate-limiting step for NO formation is the same as that for degradation. Thus, the rate-limiting process of NO formation from FK409 is due to the deprotonation reaction of the hydrogen atom at the 5-position by hydroxyl ions. The deprotonation process appears to be an essential step for both FK409 degradation and NO release. On the basis of the results, a possible kinetic scheme for NO release from FK409 is proposed.

Buffers↗
PubMed1995

Developmental toxicity of dinitroaniline herbicides in rats and rabbits. I. Trifluralin.

The potential developmental toxicity of trifluralin was evaluated in rats and rabbits. Pregnant rats and rabbits were dosed once daily by gavage on Gestation Days 6-15 and 6-18, respectively. Doses for rats were 0, 100, 225, 475, or 1000 mg/kg; doses for rabbits were 0, 100, 225, or 500 mg/kg. Cesarean sections were performed on rats and rabbits on Gestation Days 20 and 28, respectively. In rats, maternal toxicity was indicated in the 475 and 1000 mg/kg treatment groups by depression of body weights and food consumption. Fetal viability and morphology were not adversely affected at any dose level. Developmental toxicity was indicated at the 1000-mg/kg dose level by depression of fetal weight. The NOAEL for maternal toxicity in the rat was 225 mg/kg; the NOAEL for developmental toxicity in the rat was 475 mg/kg. In rabbits, maternal toxicity was indicated at the 225 and 500 mg/kg dose levels by abortions and/or deaths in conjunction with anorexia and cachexia. Developmental toxicity was indicated at the 500 mg/kg dose level by depressed fetal viability and weight. Fetal morphology was not adversely affected at any dose level. The NOAELs for maternal and developmental toxicity in the rabbit were 100 and 225 mg/kg, respectively. Based on these data, trifluralin did not exhibit selective toxicity toward the developing conceptus.

Aniline Compounds↗
PubMed2001

Implication of manganese (III), oxalate, and oxygen in the degradation of nitroaromatic compounds by manganese peroxidase (MnP).

The fungal ligninolytic enzyme manganese peroxidase (MnP) is known to function by oxidizing Mn(II) to Mn(III), a powerful oxidant. In this work, an abiotic system consisting of Mn(III) in oxalate buffer under aerobic conditions (Mn(III)/oxalate/O2 system) was shown to be capable of extensively transforming 2-amino-4,6-dinitrotoluene (2A46DNT)--one of the main reduction products of 2,4,6-trinitrotoluene (TNT). No significant transformation occurred in the presence of other organic acids or under anaerobic conditions. The Mn(III)/oxalate/O2 system was also able to transform other nitroaromatic compounds such as 2-nitrotoluene, 4-nitrotoluene, 2,4-dinitrotoluene, TNT - the latter to a lesser extent -, and their reduction derivatives. The Mn(III)/oxalate/O2 system mineralized 14C-U-ring labeled 2A46DNT slightly, while no significant mineralization of 14C-U-ring labeled TNT was observed. Unidentified 14C-transformation products were highly polar. Electron spin resonance experiments performed on the Mn(III)/oxalate/O2 system revealed the generation of formyl free radicals (*COO-). The oxygen requirement for the transformation of nitroaromatic compounds suggests the involvement of superoxide free radicals (O2-*). produced through autoxidation of *COO- by molecular oxygen. The implication of such a Mn(III)/oxalate/O2 system in the MnP-catalyzed degradation of nitroaromatic pollutants by white-rot fungi is further discussed.

Agaricales↗