The Interactions of a Homologous Series of Cationic Surfactants with Bovine Serum Albumin (BSA) Studied Using Surfactant Membrane Selective Electrodes

Abstract

The binding of a homologous series of n-alkyltrimethylammonium bromides to bovine serum albumin were measured in 2.7 mM phosphate buffer, pH 7.0, and at various temperatures using surfactant membrane selective electrodes as a fast and accurate method. The obtained binding isotherms have been analyzed and interpreted using the binding capacity concept, Hill equation and Wyman binding potential. The system behaved as a system with two sets of binding sites in all studied situations. The results represent the essential role of hydrophobic interactions in the first binding set. At high cationic surfactant concentrations, the occupation of the second binding set occurred, with an accompanying unfolding and exposure of numerous hydrophobic binding sites. However, this unfolding process occurred for the cationic surfactant at much higher concentrations than was required for sodium dodecyl sulfate. The Gibbs free energy change calculated on the basis of the Wyman binding potential concept decreases in the initial stages of binding and passes through a minimum, followed by occupation of the second binding set. The affinity of binding increased with increasing temperature, indicating an endothermic and essentially entropy driven process.

An insight into the micellization of dodecyldimethylethylammonium bromide (DDAB) in the presence of bovine serum albumin (BSA)

“…The three regions outlined are in line with regions observed during interactions between a homologous series of n-alkyltrimethylammonium bromides and BSA [15] studied using surfactant selective membrane electrodes. It was also demonstrated [15] that hydrophobic interactions play an important role in BSA-surfactant binding.…”

“…It was also demonstrated [15] that hydrophobic interactions play an important role in BSA-surfactant binding. The findings in the present work support the fact that although in less extent, cationic surfactants like anionic surfactants can also induce conformational changes in the proteins.…”

“…In contrast to anionic surfactant, the literature on complexation of cationic surfactants and water-soluble proteins is limited [15][16][17]. Ajloo et al [17] have investigated the interactions between hemoglobins and cationic surfactant dodecyl trimethylammonium bromide (DTAB) and found that autooxidation of these proteins could be enhanced in the presence of DTAB.…”

Multiple thin film formation from dilute mixtures of polyethyleneimine (PEI) and cetyltrimethylammonium bromide (CTAB)

“…In particular, surfactant selective electrodes have been widely used to study the binding of ionic surfactants to charged and neutral macromolecules [4,7,8]. Potentiometric surfactant selective electrodes can directly measure and monitor the concentration of unassociated surfactant unimers in the presence or absence of additives, provided the membrane works in the direct mode under good statistical and calibrated control [9,10]. However, the indirect mode via potentiometric titrations is the best choice when measuring the total amount of surfactant present in solution [11][12][13].…”

Surfactantion-selective electrodes: A promising approach to the study of the aggregation of ionic surfactants in solution

“…87 SISEs have also been successfully used for investigating the other ionic surfactant-globular protein interactions. [177][178][179] The interaction between DNA and cationic surfactants has been studied intensively. 91,153,173,174,180,181 However, many aspects of surfactant interactions with DNA are not yet completely understood.…”