Ionic surfactants ionize in solution to generate a charged group. Residues with opposite charges to proteins are combined with each other through electrostatic interactions, such as anionic surfactants and positively charged residues of proteins such as lysine, arginine, and groups. Acid binding; cationic surfactants bind to negatively charged residues, such as aspartic acid and glutamic acid. After electrostatic binding, the hydrophobic end of the surfactant binds to the hydrophobic site near the protein.
For non-ionic surfactants and diionic surfactants, which are two types of electrically neutral surfactants, they bind to proteins with relatively weak forces in solution, such as hydrophobic forces and hydrogen bonds. Such interactions are usually Does not cause a strong change in protein conformation.

The interaction between surfactant and protein is not only related to the type, but also to the concentration. The same surfactants cause different degrees of protein conformational changes at different concentrations. As mentioned earlier, ionic surfactants are strong protein denaturants, but at low concentrations, ionic surfactants can also increase the thermal stability of some proteins. Japanese scholars have found that the presence of a small amount of SDS can effectively enhance the thermal stability of BSA, and the longer the alkyl chain, the more significant the protective effect. One of the main functions of BSA in the body is to transport amphiphilic molecules, small hydrophobic molecules, etc. In its natural state, BSA has 12 sulfonate binding sites. When the number of SDS bound by a BSA is 12 (maximum 15), SDS can stabilize. When the number of bound SDS exceeds 15, BSA begins to tend to unfold the structure, which exposes more binding sites, resulting in further unstable protein conformation. Different proteins can bind different amounts of SDS in their natural state: β-lactoglobulin contains 1 binding site; α-spiral tauryl coenzyme-A binding protein (ACBP) can bind 1-3 SDS; α-whey The protein is invariant in the case of binding 3-4 SDS. However, SDS at low concentrations does not always play a role in maintaining protein stability, such as myoglobin, even if only one SDS is combined, it can cause the protein to be extremely unstable.