Ascorbic acid reaction with disulphide compounds: effects and applications

A method was developed for estimation of concentrations of cystine based on the reaction of this oxidised amino acid with ascorbic acid and copper ion. The standard curve which was constructed was used as the basis for investigation of the effects which both cystine and glutathione disulphide, and some disulphide proteins, exerted on the amount of hydrogen peroxide formed in the reaction of ascorbic acid. The hydrogen peroxide product was lowered in the presence of the disulphide compounds. The disulphide compounds also lowered the amount of deoxyribose reacting material formed during the ascorbic acid oxidation. The reaction between ascorbic acid and copper and cystine was used to estimate the amount of the disulphide amino acid in acid digests of proteins.     

Polymer-brush stationary phases for open-tubular capillary electrochromatography

Synthesis of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes from the inside of silica capillaries by surface-initiated atom transfer radical polymerization (ATRP) yields unique stationary phases for open-tubular capillary electrochromatography (OT-CEC). Although PHEMA brushes have only a small effect on the separation of a set of phenols and anilines, derivatization of PHEMA with ethylenediamine (en) allows baseline resolution of several anilines that co-elute from bare silica capillaries. Derivatization of PHEMA with octanoyl chloride (C8-PHEMA films) affords even better resolution in the separation of a series of phenols and anilines. Increasing the thickness of C8-PHEMA coatings by a factor of 2 enhances resolution for several solute pairs, presumably because of an increase in the effective stationary phase to mobile phase volume ratio. Thus, this work demonstrates that thick polymer brushes provide a tunable stationary phase with a much larger phase ratio than is available from monolayer wall coatings. Through appropriate choice of derivatizing reagents, these polymer brushes should allow separation of a wide range of neutral molecules as well as compounds with similar electrophoretic mobilities.     

Efficient palladium-catalyzed nucleophilic addition of triorganoindium reagents to carbocyclic derivatives

Palladium (0)-catalyzed allylic substitution reactions employing triorganoindium reagents have been investigated. In situ generated vinyl- and arylindiums react with substituted and unsubstituted cyclohex-2-enyl esters in the presence of 1-3 mol % Pd(2)(dba)(3) to produce vinyl- or arylcyclohexenes in moderate to excellent yields. The stereoselectivity of this process was also examined, and evidence is presented that the reaction proceeds with inversion of stereochemical configuration.