María J. Suárez

Effect of alcohols on the micellar properties in aqueous solution of alkyltrimethylammonium bromides

The effect ofn-butanol,n-propanol, andn-hexanol on the critical micelle concentration (CMC) and degree of ionisation of the micelles of dodecyl-, tetradecyl- and hexadecyltrimethylammonium bromides in aqueous solution has been determined by conductimetric techniques. Increase of the molality of added alcohol over the concentration ranges examined (up to 0.3 mol kg−1 butanol, 0.07 mol kg−1 pentanol and 0.025 mol kg−1 hexanol) caused a progressive decrease of CMC and increase of the degree of ionisation for each surfactant-alcohol system. At a constant molality of added alcohol the degree of ionisation increased with a) an increase of the chain length of the surfactant for each alcohol and b) an increase of the chain length of the alcohol for each surfactant. The distribution of each alcohol between the aqueous and micellar phases and the free energy of solubilization were determined from the change of CMC with molality of added alcohol.

Mixed micelles of n-alkyltrimethylammonium bromides: influence of alkyl chain length

The influence of chain length on the composition of micelles in a binary mixture of n-hexyltrimethylammonium bromide and n-octyl-, n-decyl-, n-dodecyl-, n-tetradecyl- and n-hexadecyltrimethylammonium bromides has been determined from an analysis of the variation of the critical micelle concentration (determined by conductivity techniques) as a function of solution composition. Using the theoretical treatment of Motomura, the composition of each compound in mixed micelles was evaluated. The nonideality of mixing was expressed in terms of the molecular interaction parameter β, obtained with the Holland and Rubingh theory. The molecular thermodynamic model of Puvvada and Blanckschtein was used to study the nonideal behaviour of the mixtures.

A spectroscopic study of the interaction catalase–cationic surfactant (n-decyltrimethylammonium bromide) in aqueous solutions at different pH and temperatures

A surfactant-induced and temperature conformational transition of catalase has been examined by difference spectroscopy for n-decyltrimethylammonium bromide (C10TAB) in different media (pHs 3.2, 6.4 and 10.0). The conformational transition of catalase by C10TAB was followed as a function of denaturant concentration using absorbance measurements at 280 nm and the data were analysed to obtain the Gibbs energy of the transition in water (ΔG0w) and in a hydrophobic environment (ΔG0hc) for saturated protein–surfactant complexes. Changes in absorbance at 280 nm of catalase with temperature were used to determine the parameters characterising the thermodynamics of unfolding, melting temperature (Tm), enthalpy (ΔHm), entropy (ΔSm) and heat capacity (ΔCp). The results suggest that catalase interacts with C10TAB in the media of pHs 6.4 and 10.0 inducing a conformational transition. However, an interaction in acid medium of pH 3.2 was not present. Finally, we compared the interaction of catalase with other cationic surfactants studied by other authors.

Secondary structure of prothymosin alpha evidenced for conformational transitions induced by changes in temperature and concentration of n-dodecyltrimethylammonium bromide.

Abstract. Conformational changes of prothymosin α (ProTα) induced by changes in temperature and concentration of the denaturant n-dodecyltrimethylammonium bromide (C12TAB) were studied by difference spectroscopy. The conformational transition of ProTα by C12TAB was followed as a function of denaturant concentration by absorbance measurements at 230xa0nm and the data were analyzed to obtain the Gibbs energy of the transition in water

A Comparison of the Micellar Properties of Structurally Related Antidepressant Drugs

nleft( {Delta G_{rm w}^0 } right)n

Concentration Dependence of the Osmotic and Activity Coefficients of Imipramine and Clomipramine Hydrochlorides in Aqueous Solution

n and in a hydrophobic environment

Activity and osmotic coefficients of promethazine and chlorpromazine hydrochlorides in aqueous solutions of low ionic strength

nleft( {Delta G_{{rm hc}}^0 } right)n