An intrinsically disordered protein in F127 hydrogel: Fluorescence correlation spectroscopy and structural diversity of beta casein

Abstract

Intrinsically Disordered Proteins (IDPs) switch between diverse structures which prevents them from crystallization. FCS of the IDP beta casein (β-CN), labeled with Alexa488, suggests that in buffer the structure fluctuates between a highly extended state (radius 34.5 ± 7 nm) and a highly collapsed state (radius 1 nm). To understand their behavior in a highly crowded environment, like the cell, β-CN was studied inside a pluronic copolymer (F127) where a 2-times higher rotational and 10–16 times higher translational friction were observed. Fluorescence emissions of Tryptophan indicate that the protein is localized at corona region exposing to the void region of the gel.