Chiral capillary electrophoresis and nuclear magnetic resonance investigation on the structure-enantioselectivity relationship in synthetic cyclopeptides as chiral selectors

In the present work, synthetic cyclohexa- and cycloheptapeptides previously singled out by a combinatorial chemistry approach have been evaluated as chiral selectors in capillary electrophoresis. By applying the countercurrent migration technique and employing a new adsorbed coating, a series of dinitrophenyl amino acids as well as some chiral compounds of pharmaceutical interest have been evaluated for enantiorecognition. The results thus obtained led to a deeper investigation of the chiral discrimination process, by carrying out nuclear magnetic resonance (NMR) studies on selected cyclopeptide-analyte complexes. These studies shed light on the chemical groups involved in the analyte-selector interaction and provided useful information for a wider application of these cyclopeptides in the separation of other drug enantiomers.     

A Mathematical Model of the Carbon Arc Reactor for Fullerene Synthesis

A mathematical model of the carbon arc process for the synthesis of fullerenes (C ₆₀ , C ₇₀ ) is developed. The two-dimensional model solves for the velocities, temperature, and total concentration of carbon species. The net emission coefficient method is used for the radiation term. The carbon species conservation equations consider the evaporation of carbon from the anode, cathode surface deposition, and carbon condensation. The thermodynamic and transport properties are calculated as a function of temperature and carbon mass fraction, using the method of Chapman–Enskog. Erosion rates used by the model are determined experimentally. Calculated fields of the velocities, temperatures, carbon mass fraction and current intensity are presented. Comparison is made of the behavior of the arc at 1 and 4 mm interelectrode gaps, and between operation in argon and in helium. The results of simulations provide a justification for the higher yields observed in helium compared to the argon case.     

Studies on the extraction of Copper(II) with 4-alkyldithiocarboxylate derivatives of 1-phenyl-3,5-dioxopyrazolidine

The extraction behaviour of copper(II) from acid solutions (pH 0-6) was studied with the new reagent 4-alkyldithiocarboxylate-3,5-dihydroxy-l-phenylpyrazol (HL; alkyl = n-butyl, n-dodecyl). The species extracted was found to be ML(2). The reagent was used to separate copper(II) from iron(III) in an acidic lixiviation solution of a mineral sample composed of enarguite (Cu(3)AsS(4)) and pyrite (FeS(2)). Additionally, the extraction efficiency of this new reagent was compared with the commercially available LIX 984 N extradant of copper (II).     

Wave propagation and Landau-type damping in liquids

Intermolecular forces are modeled by means of a modified Lennard-Jones potential, introducing a distance of minimum approach, and the effect of intermolecular interactions is accounted for with a self consistent field of the Vlasov type. A Vlasov equation is then written and used to investigate the propagation of perturbations in a liquid. A dispersion relation is obtained and an effect of damping, analogous to what is known in plasmas as “Landau damping”, is found to take place.     

Stability of peeling for systems with rate independent decohesion energy

The stability of peeling is theoretically investigated for systems with rate independent decohesion energy. The effects of the system stiffness, tape geometry and variation of the bonding energy along the tape-substrate interface are analyzed. The conditions for having stable (controlled) or unstable (brutal) peeling are obtained analytically. The problem studied can provide insights on possible instabilities affecting the detachment process of gecko’s toes and other biological systems.     

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.     

Electrosynthesis of a Bis-Ketenedithioacetal Disulphide Derivative From 1-Phenyl-3-Methyl-4-Butyldithiocarboxylate-5-Pyrazolone Using a Glassy Carbon Electrode

The electrooxidation of 1-phenyl-3-methyl-4-butyldithiocarboxylate-5-pyrazolone 1 has been studied in ethanol/water solution, using a glassy carbon electrode surface. The electrochemical and spectroscopic data are in agreement with a bis-ketenedithioacetal disulphide compound 2 as the only product of the reaction.