Unfolding and Refolding of Protein by a Combination of Ionic and Nonionic Surfactants

Abstract

The interaction of protein and surfactant yields protein–surfactant complexes which have a wide range of applications in the cosmetics, foods, and pharmaceutical industries among others. Ionic and nonionic surfactants are known to interact differently with the protein. The interplay of electrostatic and hydrophobic interactions governs the resultant structure of protein–surfactant complexes. The present study enlightens the paramount role of the hydrophobic interaction, tuned by the hydrophobic tail length of ionic surfactants, in the unfolding of anionic bovine serum albumin (BSA) protein. The unfolding of BSA in the presence of four different tail-length cationic surfactants, that is, C10TAB, C12TAB, C14TAB, and C16TAB, has been investigated by small-angle neutron scattering and dynamic light scattering. All cationic surfactants unfold the protein at a certain concentration range. The propensity of protein unfolding increases with increasing the hydrophobic tail length. The denatured structure of BSA upon addition of cationic surfactants is characterized by the random flight model representing a beads-on-a-string chain-like complex. The unfolded protein binds the surfactant micelles in the protein–surfactant cluster. The micelles get elongated with the increasing concentration of cationic surfactants, whereas the number of micelles per cluster is decreased. In the final stage, the protein–surfactant cluster merges to one large micelle with unfolded protein wrapping the micelle surface. The pathway of protein unfolding is described in terms of the changes in the micellar size, the number of micelles formed per cluster, the separation between the micelles in the cluster, the aggregation number of micelles, and the number of proteins per cluster. The protein–surfactant interaction is further examined in the presence of a nonionic surfactant, that is, C12E10. The nonionic surfactant significantly suppresses the interaction of BSA protein with ionic surfactants by forming mixed micelles. As a result of the mixed micelles formation by ionic–nonionic surfactants, the ionic surfactant moves out from the unfolded BSA protein, and this enables the protein to refold back to its native structure. The propensity of mixed micelle-driven refolding of proteins is significantly changed with changing the tail length of the ionic surfactant.

Sans Studies on the Bovine Serum Albumin Denaturation in the Presence of SDS

“…The results of this research agreed with other previous studies with different techniques, for example, Y. Ding et.al [8] reported from the FF-TEM data that BSA has loosened their globular structure at low concentration of SDS. The further expand of the BSA occured in the high concentration of SDS.…”

“…BSA is quite easy to obtain, ease of purification, low cost, and has unusual ligand-binding properties made BSA a good model to study the protein surfactant interaction. Sodium dodecyl sulfate (SDS) is an anionic surfactant that is known to have good binding ability to protein compared to several other surfactant molecules such as guanidinium chloride or urea [8].…”

From Nanoparticle Heteroclusters to Filament Networks by Self-Assembly at the Water–Oil Interface of Reverse Microemulsions

“…The assessment of structure factors for the analysis of small-angle scattering data from aggregates has been discussed in detail recently by Larsen, Pedersen, and Arleth . We found that the simplest structure factor for our purpose is the random flight structure factor as used, for example, for the analysis of protein–surfactant complexes. , It should be noted that it is also named “random flight beads-on-a-string structure factor”, for example, to describe the structure of sodium dodecyl sulfate micelles organized along a protein chain, α-synuclein . Briefly, in the present study, the first term in eq will be replaced by the scattering of a “random flight cluster” where I ( q ) is the scattering intensity of noninteracting particles according to eq and S ( q ) is the structure factor of the random flight model with a constant step size …”

Controllable enzymatic superactivity of α-chymotrypsin activated by the electrostatic interaction with cationic gemini surfactants

“… 2 The highly regarded topics in the field in recent years are still focused on to explore how to maintain and enhance the activity and/or stability of enzymes. 3 …”