Thermochemically induced binding of methyl orange to polycations containing primary amine groups

The thermochemical transformation of electrostatically formed complexes of methyl orange (MO) with polycations containing primary amine groups such as ammonium salts afforded new polymers with a high concentration of covalently bound 4‐N,N‐dimethylaminoazobenzene groups in the side chain. Poly(allylamine hydrochloride) and poly(β‐aminoethylene acrylamide hydrochloride) were employed as support polycations for MO. The transformation of sulfonate–ammonium ion pairs into sulfonamide bonds, via heating at an elevated temperature, was supported by the polymer properties before and after the thermal treatment. The polymer structure changes were monitored with elemental analysis, Fourier transform infrared, ¹H NMR, and ultraviolet–visible absorption spectroscopy, and thermogravimetric analysis. The spacer length between the backbone and azobenzene structures used as side chains strongly influenced the polymer properties before and after the heat‐induced reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5898–5908, 2006     

Indirect fluorometric determination of diclofenac sodium.

A simple and easy method of analysis for diclofenac sodium is reported. A spectrofluorometric method for the microdetermination of diclofenac sodium has been developed through its reaction with cerium(IV) in an acidic solution and measurement of the fluorescence of the Ce(III) ions produced. Under the optimum experimental conditions for the oxidation reaction, 1.0 M H2SO4 with 90 min of heating time (100 degrees C), the range of application is 124.3-600 ng mL(-1) and the limit of detection is 72.7 ng mL(-1). The proposed method was applied to the determination of diclofenac sodium in pharmaceutical tablets. The results of the analysis show a good agreement with those obtained by the official USP 27 HPLC method.     

Tröger's base scaffold in racemic and chiral fashion as a spacer for bisdistamycin formation. Synthesis and DNA binding study

‘Head-to-head’ oligo-N-methylpyrrole peptide dimers linked by a methano[1,5]diazocin scaffold are presented in racemic as well as chiral fashion. Their DNA binding activities were assayed on calf thymus DNA, poly(dA-dT)₂, and poly(dC-dG)₂ by NMR and ECD spectroscopies, and fluorescence probe displacement assay. The presented dimers prefer AT sequences, but show higher affinity to poly(dC-dG)₂ than distamycin A. The (4R,9R) configuration of methanodiazocin bridge was found to be better suited for interaction with ct-DNA and poly(dA-dT)₂ than (4S,9S) configuration.     

High-performance liquid chromatographic determination of cocaine and benzoylecgonine by direct injection of human blood plasma sample into an alkyl-diol-silica (ADS) precolumn

A column-switching high-performance liquid chromatographic method with UV detection for the determination of cocaine (COC) and benzoylecgonine (BZE) in human blood plasma samples is described. The method uses an alkyl-diol-silica ADS-C18 extraction precolumn. A 50- micro L plasma sample was introduced to the ADS precolumn in order to separate the analytes from proteins and endogenous compounds. The fraction containing COC and BZE was back-flushed and transferred to an Alltech mixed-mode C(18)/cation-exchange analytical column for final separation. The validation of the method revealed quantitative recoveries from 95.0 to 99.0% for COC at three different concentrations (0.5, 1.0 and 2.0 micro g mL(-1)), and from 96.0 to 99.0% for BZE at the same concentration levels with coefficients of variation <4.00% (n=5). The detection limit (signal to noise ratio (S/N)>3) was 0.03 micro g mL(-1) for all the compounds with an injection volume of 50 micro L. However, it was possible to enhance the sensitivity further by injecting larger plasma volumes, up to 200 micro L, at the same optimal conditions. The overlap of sample preparation, analysis and reconditioning of the extraction column, increase the overall sample throughput to 5 samples h(-1). The developed method has been applied to human blood plasma samples from subjects suspected of cocaine abuse.     

Coordinating ability of the heterocycles 1,3-dithia-2-arsa- and stiba-cyclopentanes. Part III. Dithioacid and dithiocarbamate complexes containing a free functional group. Crystal structure of 2-pyrrolidonedithiocarbamate of 1,3-dithia-arsa-cyclopentane

Three 1,1-dithioacids containing an additional functional group, 2-pyrrolidone-1-carbodithioic acid, 2-hydroxycyclopentene-1-carbodithioic acid, and 2-pyrrolidone-1,3-bis(carbodithioic) acid, were reacted with the Group 15 heterocycles 2-chloro-1,3-dithia-2-arsa- and stiba-cyclopentanes (CIMS₂C₂H₄; M = As, Sb). The dithiocomplexes obtained were characterized by spectroscopic methods and elemental analyses. The X-ray structure determination of the 2-pyrrolidonedithiocarbamate of 1,3-dithia-arsacyclopentane shows a monodentate behavior of the dithiocarbamate entity and the absence of participation of the carbonyl oxygen in the coordination.     

Melatonin Rescues the Dendrite Collapse Induced by the Pro-Oxidant Toxin Okadaic Acid in Organotypic Cultures of Rat Hilar Hippocampus

The pro-oxidant compound okadaic acid (OKA) mimics alterations found in Alzheimer’s disease (AD) as oxidative stress and tau hyperphosphorylation, leading to neurodegeneration and cognitive decline. Although loss of dendrite complexity occurs in AD, the study of this post-synaptic domain in chemical-induced models remains unexplored. Moreover, there is a growing expectation for therapeutic adjuvants to counteract these brain dysfunctions. Melatonin, a free-radical scavenger, inhibits tau hyperphosphorylation, modulates phosphatases, and strengthens dendritic arbors. Thus, we determined if OKA alters the dendritic arbors of hilar hippocampal neurons and whether melatonin prevents, counteracts, or reverses these damages. Rat organotypic cultures were incubated with vehicle, OKA, melatonin, and combined treatments with melatonin either before, simultaneously, or after OKA. DNA breaks were assessed by TUNEL assay and nuclei were counterstained with DAPI. Additionally, MAP2 was immunostained to assess the dendritic arbor properties by the Sholl method. In hippocampal hilus, OKA increased DNA fragmentation and reduced the number of MAP2(+) cells, whereas melatonin protected against oxidation and apoptosis. Additionally, OKA decreased the dendritic arbor complexity and melatonin not only counteracted, but also prevented and reversed the dendritic arbor retraction, highlighting its role in post-synaptic domain integrity preservation against neurodegenerative events in hippocampal neurons.     

The Role of Information in Managing Interactions from a Multifractal Perspective

In the framework of the multifractal hydrodynamic model, the correlations informational entropy–cross-entropy manages attractive and repulsive interactions through a multifractal specific potential. The classical dynamics associated with them imply Hubble-type effects, Galilei-type effects, and dependences of interaction constants with multifractal degrees at various scale resolutions, while the insertion of the relativistic amendments in the same dynamics imply multifractal transformations of a generalized Lorentz-type, multifractal metrics invariant to these transformations, and an estimation of the dimension of the multifractal Universe. In such a context, some correspondences with standard cosmologies are analyzed. Since the same types of interactions can also be obtained as harmonics mapping between the usual space and the hyperbolic plane, two measures with uniform and non-uniform temporal flows become functional, temporal measures analogous with Milne’s temporal measures in a more general manner. This work furthers the analysis published recently by our group in “Towards Interactions through Information in a Multifractal Paradigm”.     

Matrix-assisted laser desorption/ionization tandem reflectron time-of-flight mass spectrometry of fullerenes

Atandem reflectron time-of-flight mass spectrometer developed in our laboratory provides a unique opportunity to investigate the collision-induced dissociation of fullerene ions formed by matrix-assisted laser desorption/ionization (MALDI). Specifically, this opportunity arises from the ability to utilize high energy collisional activation (normally available only on tandem sector instruments by using continuous ionization techniques) for ions formed by pulsed laser desorption, whereas most MALDI time-of-flight instruments record product ion mass spectra of ions formed by metastable or postsource decay. In this study we investigate the products of mass-selected and collisionally activated C ₆₀ ⁺ and C ₇₀ ⁺ ions by using different target gases over a range of target gas pressures. In general, heavier target gases produce more extensive fragmentation and improve the mass resolution of lower mass ionic products because a greater portion of these ions are formed by single collisions. Additionally, the tandem time-of-flight instrument utilizes a nonlinear (curved-field) reflectron in the second mass analyzer that enables high energy collision-induced dissociation spectra to be recorded without scanning or stepping the reflectron voltage.     

Modification of PP fibres with alkaline copolyamides

Copolyamides with 5.9‐19.7 wt.% of nylon salt ADETA (adipic acid + diethylenetriamine) and 94.1‐80.3 wt.% of ϵ‐caprolactam were synthesized and their properties were estimated. Blended polypropylene/copolyamides fibres containing 5‐15 wt.% of copolyamides were prepared and their properties were evaluated. The electrical properties, hydrophilicity and especially dyeability of modified PP fibres are positively influenced by a higher amount of the copolyamide in the PP and also by a higher amount of the nylon salt ADETA in the copolyamide.