Evaluation of calibration data in capillary electrophoresis using artificial neural networks to increase precision of analysis

An RP-HPLC study for the pKa determination of a series of basic compounds related to caproctamine, a dibenzylaminediamide reversible inhibitor of acetylcholinesterase, is reported. The 2-substituted analogues, bearing substituents with different electronegativity, were analysed by RP-HPLC by using C18 C4 stationary phases with a mobile phase consisting of mixture of acetonitrile and triethylamine phosphate buffer (pH range comprised between 4 and 10). Typical sigmoidal curves were obtained, showing the dependence of the capacity factors upon pH. In general, the retention of the investigated basic analytes increased with increasing of the pH. The inflection point of the pH sigmoidal dependence was used for the dissociation constant determination at a fixed acetonitrile percentage. When plotting pKa vs. percent of acetonitrile in the mobile phase for two representative compounds, linear regression were obtained: the y intercept gave the aqueous pKa(w). The pKa estimation by HPLC method was found to be useful to underline the difference of benzylamine basicity produced by the ortho aromatic substituents. The variation of pKa values (6.15-7.80) within the series of compounds was correlated with the electronic properties of the ortho-substituents through the Hammett sigma parameter, whereas the ability of substituents to accept H-bond was found to play a role in determining the conformational behavior of the molecules.     

Algèbre de Clifford et formules de frenet

Clifford Algebra generalizes easily curvature and torsion inR(n,0) and Frenet formulas     

Interaction of Boron Nitride Nanosheets with Model Cell Membranes

Boron nitride nanomaterials have attracted attention for biomedical applications, due to their improved biocompatibility when compared with carbon nanomaterials. Recently, graphene and graphene oxide nanosheets have been shown, both experimentally and computationally, to destructively extract phospholipids from Escherichia coli. Boron nitride nanosheets (BNNSs) have exciting potential biological and environmental applications, for example the ability to remove oil from water. These applications are likely to increase the exposure of prokaryotes and eukaryotes to BNNSs. Yet, despite their promise, the interaction between BNNSs and cell membranes has not yet been investigated. Here, all‐atom molecular dynamics simulations were used to demonstrate that BNNSs are spontaneously attracted to the polar headgroups of the lipid bilayer. The BNNSs do not passively cross the lipid bilayer, most likely due to the large forces experienced by the BNNSs. This study provides insight into the interaction of BNNSs with cell membranes and may aid our understanding of their improved biocompatibility.     

Synthèse et étude physico-chimique de sulfures,sulfoxydes et sulfones en série thiazolique

The alkylation of Δ⁴-thiazoline-2-thiones under phase transfer catalysis conditions leads to the corresponding thioethers in good yields. The oxidation of 2-alkylthiazoles with m-chloroperbenzoic acid leads to the corresponding sulfines or sulfones depending on experimental conditions in yields of about 80-90%. The characteristic gle, tlc, ir, ¹H nmr and ms data are reported for most of the compounds studied.     

Generalized brillouin theorem for multiconfigurational SCF theories

The matrix elements of the total Hamiltonian between a multiconfigurational SCF wave function and some well-defined linear combinations of excited Slater determinants are equal to zero. By means of this generalized Brillouin theorem it is possible to estimate the improvements to be expected from a subsequent configuration-interaction treatment. The expression of the effective potential for the orbitals can be also derived in the frame of a given multiconfigurational theory. As an example, the case of the CMC-SCF method recently suggested [9] is examined.     

Etude dans la série des radicaux hétérocycliques. Partie XV. Décomposition aprotique de l'amino-6-éthyl-2-benzothiazole dans des substrats aromatiques et hétéroaromatiques: préparation des mésityl-6- et furyl-6-éthyl-2-benzothiazoles,des sels quaternaires et des spiropyrannes correspondants

Study of heteroaromatic radicals. Part XV .

1 Partie XIV: cf. [1].

Aprotic decomposition of 6-amino-2-ethylbenzothiazole in aromatic and heteroaromatic substrates: preparation of 6-mesityl- and 6-furyl-2-ethylbenzothiazoles and of the corresponding quaternary salts and spyropyrans In the presence of excess isopentyl nitrite in aprotic solvent, the 6-amino-2-ethyl-benzothiazole leads to 6-aryl- and 6-heteroaryl-2-ethylbenzothiazoles 1 to 14 in ca. 20–50% yield (Scheme 1, Table 1). The 2-ethyl-6-benzothiazolyl radicals generated during these reactions exhibit a weak electrophilic character (Table 2). Preparatively this method has been applied to the synthesis of 6-mesityl- and 6-furyl-2-ethylbenzothiazoles 6 and 7 , which were used to prepare the corresponding quaternary salts 15 , 16 and the spiropyrans 19, 20 (Scheme 4).     

Bioactive Pectin-Murta (Ugni molinae T.) Seed Extract Films Reinforced with Chitin Fibers

This study investigated the biocomposite pectin films enriched with murta (Ugni molinae T.) seed polyphenolic extract and reinforced by chitin nanofiber. The structural, morphological, mechanical, barrier, colorimetric, and antioxidant activity of films were evaluated. The obtained data clearly demonstrated that the addition of murta seed extract and the high load of chitin nanofibers (50%) provided more cohesive and dense morphology of films and improved the mechanical resistance and water vapor barrier in comparison to the control pectin film. The antioxidant activity ranged between 71% and 86%, depending on the film formulation and concentration of chitin nanofibers. The presented results highlight the potential use of chitin nanofibers and murta seed extract in the pectin matrix to be applied in functional food coatings and packaging, as a sustainable solution.     

Chromium Speciation Using Ion Chromatography-Atomic Absorption System with On-Line Preconcentration

A method using ion chromatography-atomic absorption system (IC-AA) with on-line preconcentration unit is developed for the speciation of chromium in aqueous samples. Both Cr(III) and Cr(VI) species are pre-treated with sodium salt of ethylenediaminetetraacetic acid (EDTA) in consecutive steps. The treated samples can then be injected into an on-line preconcentration unit followed by ion chromatographic separation with UV or selective flame AA detection. Both chromium species can be separated within 10 minutes, and the method is applicable for aqueous samples with ppm levels of chromium.     

Cyclophosphazenes and Relatives as Anticancer Drugs

Abstract

Aziridinocyclophosphazenes N₃P₃Az₆ (code name MYKO 63), N₄P₄Az₈ (code name MYKO 83) and relatives constituted the first generation of anticancer drugs whose efficiency on several rodent neoplasms was made conspicuous in a quantitative manner from 1976 to 1978 both in our Laboratory and by EORTC Screening Pharmacology Groups¹. MYKO 63 appeared at that time as a promising drug for industrial development owing to its wide spectrum of activity and its very low mutagenicity². However, this hope failed as a consequence of a cumulative toxicity which occurs upon heavy polyinjections schedules. In other words, MYKO 63 exhibits an uncomfortable kinetics of action on the tumor - and, consequently, of excretion - presumably due (it was our assumption) to a too high chemical stability of the molecule.     

Roots of algebraic equations and Clifford algebra

If an algebraic equation onIR admits real roots it admits hyperbolic roots which are elements of the set (x ₀ + εy ₀) where ε is a Clifford number having a square equal to 1. The equation can have hyperbolic or real roots