Biophysical insights into sodium lauroyl sarcosine induced amyloid fibrillation of human serum albumin.

Sodium lauroyl sarcosinate (SLS), an anionic surfactant is known to solubilize recombinant proteins during purification processes. Though SLS has been shown to induce amyloid fibrillation in proteins, the specific role of SLS in amyloid formation remains less understood. Despite its well-established use in protein solubilization, further research is needed to clarify its potential influence on amyloid fibrillation pathways. In this context, we studied the effects of SLS on Human serum albumin (HSA) using a variety of biophysical techniques, including turbidity, right-angle Light Scattering (RLS) kinetics, Thioflavin T (ThT) binding, intrinsic fluorescence, far-UV circular dichroism (CD) and transmission electron microscopy (TEM). Turbidity measurements showed that SLS below 0.3 mM did not induce aggregation. However, when the concentration exceeded 0.3 mM, HSA aggregation was observed. The RLS kinetics data suggested the SLS-induced aggregation to be very fast. ThT fluorescence, far-UV CD, and TEM data indicated that SLS-induced HSA aggregates exhibit amyloid-like characteristics as evidenced by the high ThT fluorescence signals in the aggregated samples and the transformation of HSA's α-helical structure into mixed β-sheet structures. Molecular docking analysis complements in vitro results in that electrostatic and hydrophobic interactions between HSA and SLS at an acidic pH are involved, which may trigger the aggregation of the protein. These biophysical data suggested that while SLS is commonly used for protein solubilization, it also has a potential characteristic to promote amyloid fibrillation in protein under certain conditions, warranting further investigation into its role in amyloid fibrillation.