Exploring the affinity binding of alkylmaltoside surfactants to bovine serum albumin and their effect on the protein stability: A spectroscopic approach.

Steady-state and time-resolved fluorescence together with circular dichroism (CD) spectroscopic studies was performed to examine the interactions between bovine serum albumin (BSA) and two alkylmaltoside surfactants, i.e. n-decyl-ß-D-maltoside (ß-C10G2) and n-dodecyl-ß-D-maltoside (ß-C12G2), having identical structures but different tail lengths. Changes in the intrinsic fluorescence of BSA from static as well as dynamic measurements revealed a weak protein-surfactant interaction and gave the corresponding binding curves, suggesting that the binding mechanism of surfactants to protein is essentially cooperative in nature. The behavior of both surfactants is similar, so that the differences detected were attributed to the more hydrophobic nature of ß-C12G2, which favors the adsorption of micelle-like aggregates onto the protein surface. These observations were substantially demonstrated by data derived from synchronous, three-dimensional and anisotropy fluorescence experiments. Changes in the secondary structure of the protein induced by the interaction with surfactants were analyzed by CD to determine the contents of α-helix and ß-strand. It was noted that whereas the addition of ß-C10G2 appears to stabilize the secondary structure of the protein, ß-C12G2 causes a marginal denaturation of BSA for a protein:surfactant molar ratio as high as 1 to 100.