Competitive Process of Binding Between the Anionic Surfactants Sodium Dodecyl Sulfate and Sodium Cholate in Bovine Serum Albumin

Abstract

Summary: In this study sodium cholate (NaC) was used as a representative bile salt for the competitive binding between NaC and sodium dodecyl sulfate (SDS) in bovine serum albumin (BSA), in 0.02 M tris-HCl buffer solution at pH 7.50 and 25 8C. The NaC and SDS associations with BSA were monitored at low surfactant concentrations where only this specific binding process can develop. The applied method to monitor the binding was based on the analysis of the effect of SDS and NaC concentrations and their mixtures upon the fluorescence intensity of the BSA tryptophan residues. This consists of the measurement of the surfactant monomer partitioning between the dispersion medium and the microaggregates on the protein molecule where the binding is indicated by the quenching of the fluorescence chromophores. Experimentally, varying the protein concentration, the surfactant concentration needed to reach a given I o /I ratio (I o and I are the intensities with and without protein, respectively) was measured. The analyses, based on the average number of surfactant molecules bound on the protein, indicated that the SDS is a more efficient quencher than the bile salt. The need for 4-6 NaC bound molecules to give the same protein quenching efficiency by a single molecule of SDS was estimated. We concluded that the differences in the competitive binding on the protein are exclusively related to the quenching efficiency in the formation of the nonfluorescent fluorophorequencher complex via a physical contact and static quenching process.

Supramolecular complexes formed by the association of poly(ethyleneimine) (PEI), sodium cholate (NaC) and sodium dodecyl sulfate (SDS)

“…17,19 Our research group has extensively studied micellar systems formed by the self-assembly of copolymers 20,21 and surfactants. [22][23][24][25] We have investigated a large collection of synthetic polymers and biopolymers, [26][27][28] as well as surfactants and biosurfactants. [27][28][29][30] Interestingly, interactions between water-soluble uncharged polymers and the anionic surfactants have been widely investigated for several decades.…”

“…[22][23][24][25] We have investigated a large collection of synthetic polymers and biopolymers, [26][27][28] as well as surfactants and biosurfactants. [27][28][29][30] Interestingly, interactions between water-soluble uncharged polymers and the anionic surfactants have been widely investigated for several decades. On the other hand, few studies concerning the interactions of mixtures of bile salts and polyelectrolytes are found in the literature.…”

Sodium dodecyl sulfate promoting a cooperative association process of sodium cholate with bovine serum albumin

“…With proteins such as the BSA, binding studies with this bile salt have previously been performed but only under conditions of very low surfactant concentration were the specific binding process predominates [1,5]. In this context, we have shown that NaC binds specifically to the BSA but, in mixtures with SDS, they compete for the BSA binding site occupancy [10].…”

“…We have recently studied the competitive binding process for NaC and SDS with bovine serum albumin at low surfactant concentration in 0.02 M Tris-HCl buffer solution at pH 7.50 [10]. The analyses, based on the average number of surfactant molecules bound to the protein, indicated that SDS is a more efficient quencher than the bile salt.…”

Autoassociação de misturas dos Surfactantes Dodecanoato de Sódio (SDoD) e Decanoato de Sódio (SDeC) com o Polímero Hidrofobicamente Modificado Etil(Hidroxietil)Celulose (EHEC)

“…17 Um sistema bastante estudado é a interação PEO-SDS, onde tem sido mostrado que a cadeia polimérica se envolve ao redor da micela, e que as interações variam de acordo com o tamanho da cadeia do polímero. 5,6,10,13,[18][19][20][21][22][23] Comumente, sistemas formados por polímeros não iônicos e surfactantes iônicos são governados por forças de interação entre grupos hidrofílicos, hidrofóbicos e iônicos. Soluções aquosas de etil(hidroxietil)celulose (EHEC) com adição de um surfactante aniônico constituem um sistema típico desta classe.…”