The Influence of Surfactants on Liquid-Liquid Phase Separation of Globular Protein

Liquid-liquid phase separation (LLPS) holds a crucial role in various biological processes, encompassing protein folding, assembly, and functioning.In the present study, we studied the impact of the anionic surfactant sodium dodecyl sulfate (SDS) and neutral surfactant dodecylpyranosyl glucoside (DG) on the LLPS of bovine serum albumin (BSA) in a yttrium (III) chloride hexahydrate (YCl3) solution.The LLPS phenomenon occurs at a low critical concentration (LCC) of YCl3 and dissolves at a high critical concentration (HCC).We observed that SDS augments the LLPS region when introduced into the solution.In contrast, DG primarily reduces the YCl3's HCC while having a slight effect on the LCC.Specifically, with a fixed BSA concentration of 40 mg/mL, the LCC rises from 6 mM to 19 mM with the addition of SDS, and the HCC leaps from 8 mM to beyond 20 mM.On the contrary, with a mild DG concentration (5-7 mM), the HCC drops until the LLPS disappears around 8 mM, implying the surfactant's inhibition of phase separation.Based on the analysis of spectroscopy and dynamic light scattering, we deduce that SDS primarily modulates BSA LLPS via electrostatic interactions, whereas the suppression of LLPS by DG is largely attributable to hydrophobic associations.