Determination of oxidized and reduced glutathione, by capillary zone electrophoresis, in Brassica juncea plants treated with copper and cadmium

A rapid method of capillary zone electrophoresis is described to determine the oxidized (GSSG) and reduced (GSH) form of glutathione in plant tissue. In order to separate both analytes in a fused-silica capillary, the pH and composition of the electrolyte solution were optimized. The electrolyte composition was 100 mmol/L, borate 25 mmol/L Tris, and 0.2% w/v metaphosphoric acid (MPA), pH 8.2. Some instrumental conditions used to run the samples were hydrostatic injection for 30 s, 30 kV applied voltage, and UV detection (185 nm) at 25 degrees C. Linearity and useful range obtained for the calibration curves were optimum, with correlation coefficients about 0.999 in the 0-120 micromol/L range. The migration time was highly reproducible, less than 5 min being afforded to run a sample. Electrolyte buffer and samples required a careful pH control for optimal separation of both analytes. This aspect constitutes a critical analytical step when acids are used in the procedure for sample preparation. Simultaneous analysis of GSH and GSSG may provide a useful tool for comparative studies of plants in order to select those species with a potential capacity for detoxification from toxic elements or those appearing promising from phytoremediation for these elements.     

Efficient synthesis in three steps and spectral determination of methyl‐5‐[(o‐, m‐, and p‐substituted‐phenylthio]‐2‐benzimidazolecarbamates

The preparation and spectral properties often novel methyl 5‐[(o‐, m‐, and p‐substituted)‐phenylthio]‐2‐benzimidazolecarbamates with possible pharmacological activity as antihelmintics is described; by condensation and cyclization between 5‐methylthioures sulfate chloroformic acid methyl ester and 3,4‐diaminophenyl‐substituted‐phenylthio ether dissolved in ethanol. The structures of all final products were corroborated by ir; ¹H‐nmr, ¹³C‐nmr and ms.     

Kinetics of the Thermal and Thermo‐Oxidative Degradation of a Polystyrene–Clay Nanocomposite

Summary: Thermogravimetry and differential scanning calorimetry have been used to study the thermal and thermo‐oxidative degradation of polystyrene (PS) and a PS–clay nanocomposite. An advanced isoconversional method has been applied for kinetic analysis. Introduction of the clay phase increases the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

The change in activation energy for the degradation of PS and the PS–clay nanocomposite with the extent of polymer conversion.     

Oxalate-2-ethanolamine complexes of some bivalent cations (Mn,Co, Ni,Cu, Zn and Cd)

On the refluxing ofM(II) oxalate (M=Mn, Co, Ni, Cu, Zn or Cd) and 2-ethanolamine in chloroform, the following complexes were obtained: MnC₂O₄·HOCH₂CH₂NH₂·H₂O, CoC₂O₄·2HOCH₂CH₂NH₂, Ni₂(C₂O₄)₂·5HOCH₂CH₂NH₂·3H₂O, Cu₂(C₂O₄)₂·5HOCH₂CH₂NH₂, Zn₂(C₂O₄)₂·5HOCH₂CH₂NH₂·2H₂O and Cd₂(C₂O₄)₂·HOCH₂CH₂NH₂·2H₂O. Following the reaction ofM(II) oxalate with 2-ethanolamine in the presence of ethanolammonium oxalate, a compound with the empirical formula ZnC₂O₄·HOCH₂CH₂NH₂·2H₂O¹ was isolated. The complexes were identified by using elemental analysis, X-ray powder diffraction patterns, IR spectra, and thermogravimetric and differential thermal analysis. The IR spectra and X-ray powder diffraction patterns showed that the complexes obtained were not isostructural. Their thermal decompositions, in the temperature interval between 20 and about 900°C, also take place in different ways, mainly through the formation of different amine complexes. The DTA curves exhibit a number of thermal effects.     

UPTAKE KINETICS AND INTRACELLULAR LOCALIZATION OF HYPOCRELLIN PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY: A CONFOCAL MICROSCOPY STUDY

Hypocrellins are naturally occurring compounds with photosensitizing properties in biological systems. We have prepared synthetic derivatives of hypocrellin B, which have promise as photosensitizers in the clinical application of photodynamic therapy. The intracellular localization and uptake kinetics of hypocrellin B and several selected hypocrellin congeners were determined semiquantitatively by fluorescence confocal microscopy in monolayer cultures of EMT6/Ed murine tumor cells. Each compound had unique uptake kinetics. Although no compound tested to date has demonstrated nuclear labeling, most could be detected in lysosomes, Golgi, endoplasmic reticulum and, to a minor extent, in cellular membranes. No two compounds gave identical labeling distributions. The differences are assumed to originate in physicochemical properties characteristic of each compound, which may ultimately impact upon the primary modality of phototoxicity.     

Sulfur Compounds. 183. A Derivative of Perthiocarbonic Acid H2CS4: X-ray structural analysis of bis(triphenylmethyl) perthiocarbonate (Ph3C)2CS4

The molecular structure of Ph₃CSSC(S)SCPh₃ · CS₂ has been determined by X-ray structural analysis. The substance crystallizes in the triclinic crystal system [a = 884.9(2) pm, b = 1 039.5(2) pm, c = 2 064.6(3) pm, α = 75.86(1)°, β = 79.83(2)°, γ = 77.31(5)°, Z = 2, space group P1 ]. The CS₃ group is planar; the S? S-bond (201.4 pm) forms an angle of 5.7° with the CS₃ plane. The torsional angle CSSC equals 96.3°. (Ph₃C)₂CS₄ was obtained by reaction of TosNSCl₂ (Tos = p-MeC₆H₄SO₂) with Ph₃CSH in CS₂ in the presence of triethylamine. The reaction mechanism is discussed.     

A combined method of neutron activation analysis and radiometric measurements for <Superscript>234</Superscript>U and <Superscript>238</Superscript>U determination in soil samples of low uranium concentration

A method that combines the use of non-destructive neutron activation analysis and high-resolution α spectrometry has been developed for determination of the activities of ²³⁴U and ²³⁸U in geological samples of low uranium content. The ²³⁸U content is determined by k₀-based neutron activation analysis, whereas the ²³⁴U/²³⁸U relationship is measured by α spectrometry after isolation and electrodeposition of the uranium extracted from a lixiviation with 6 M HCl. The main advantage of the method is the simplicity of the chemical operations, including the fact that the steps destined to assure similar chemical state for the tracer and the uranium species present in the sample are not necessary. The method was applied to soil samples from sites of the North Peru Coast. Uranium concentration range 3–40 mg/kg and the isotopic composition correspond to natural uranium, with about 10% uncertainty.     

Synthesis of dibromo ketones by the reaction of the environmentally benign H<Subscript>2</Subscript>O<Subscript>2</Subscript>-HBr system with oximes

It was found that oximes undergo deoximation in the presence of the H₂O_2aq-HBr_aq system to form ketones and bromo ketones. This reaction provided the basis for the synthesis of dibromo ketones in yields varying from 40% to 94%. This method is environmentally friendly, sustainable, and easy to perform. The results of this investigation extend the potential of the use of oximes for the protection of carbonyl group, thus offering the ability to perform not only conventional deoximation but also the subsequent bromination of ketones. The reaction is easily scaled up and dibromo ketones can be prepared in gram amounts.      

Synthesis of the O-linked hexasaccharide containing β-D-Galf-(1→2)-β-D-Galf in Trypanosoma cruzi mucins

The hexasaccharide β-D-Galp-(1→2)-[β-D-Galp-(1→3)]-β-D-Galp-(1→6)-[β-D-Galf(1→2)-β-D-Galf(1→4)]-D-GlcNAc (1) is the largest carbohydrate structure released as alditol by reductive β-elimination from mucins of some strains of T. cruzi. The terminal β-D-Galp units are sites of sialylation by trans-sialidase which transfers sialic acid from the host to the parasite. Hexasaccharide 1 was synthesized by a [3 + 3]-convergent strategy based on a nitrile assisted glycosylation, using the trichloroacetimidate method. The β-D-Galf-(1→2)-β-D-Galf-D-GlcNAc synthon was sequentially constructed from the reducing end to the non-reducing end employing benzyl α-D-galactofuranoside as starting material for the internal Galf unit. The choice of this novel precursor, obtained in one-reaction step from galactose, allowed the introduction of an orthogonal and participating levulinoyl group at O-2. Thus, the diastereoselective construction of the Galf-β(1→4)-GlcNAc linkage by the trichloroacetimidate method of glycosylation was achieved. The (1)H NMR spectrum of alditol 2 was identical to the product released by β-elimination from the parasite mucin.