SDS induces amorphous, amyloid-fibril, and alpha-helical structures in the myoglobin in a concentration-dependent manner.

Amyloid fibrils have been linked to a number of diseases. Surfactants imitate plasma membrane lipids and induce amyloid fibrils. This study examined the effects of the anionic surfactant sodium dodecyl sulfate (SDS) at pH 4.5 on equine skeletal muscle myoglobin (E-Mb). To analyze the effect of SDS on aggregation and amyloid-fibril formation to E-Mb, we used various spectroscopic techniques (turbidity, light scattering, intrinsic fluorescence, ThT fluorescence, and circular dichroism (CD)), electrophoretic, and microscopic techniques. Turbidity, SDS-PAGE, and light scattering all indicated the formation of E-Mb aggregates at SDS concentrations ranging from 0.2 mM to 1.0 mM. In the presence of 0.4 mM SDS, far-UV CD and TEM data indicate that E-MB forms amorphous aggregates. ThT binding, Far-UV CD, and TEM findings indicate that E-Mb forms amyloid-like structures in the presence of 0.6-1.0 mM SDS. However, no aggregation was seen at SDS concentrations above 1 mM. In the presence of high SDS concentrations (> 1 mM), the E-Mb exhibited native-like α-helical structure. As a result, SDS exhibited three distinct behaviors: amorphous aggregates, amyloid-fibrils, and helix-inducer. These findings also shed light on how amyloid fibrils are formed when anionic surfactants are introduced, which is a significant takeaway.