Protein-Induced Dissociation of Biomolecular Assemblies

Studies on protein adsorption on nanoparticles have attracted great interest over the past years due to the unique properties of the protein-immobilized nanoparticles. However, the effects of protein adsorption on the stability of nanoparticles and the role of hydrophobic interaction in the adsorption have not been fully understood. Herein, fundamental research on protein-induced dissociation of biomolecular assemblies based on hydrophobic interaction is reported. Bovine serum albumin (BSA) is used as a model protein, and cholesterol-glutathione bioconjugate (Ch-GSH) and cholesterol-terminated polyethylene glycol (Ch-PEG) are chosen as model amphiphilic biomolecules. Ch-GSH or Ch-PEG molecules are able to self-assemble into vesicles. The walls and the coronae of the assemblies are composed of hydrophobic Ch and hydrophilic GSH (or PEG), respectively. Upon addition of BSA into phosphate buffer saline solutions of the assemblies, vesicle structures are dissociated and small-sized aggregates composed of BSA, and amphiphilic biomolecules are formed. The dissociation temperatures of the vesicles can be determined by dynamic light scattering. Transmission electron microscopy and size exclusion chromatography are used to demonstrate the dissociation of the assemblies and the formation of aggregates. The hydrophobic interaction between hydrophobic patches on BSA molecules and Ch groups in the walls of the assemblies is responsible for the dissociation of the vesicles and the formation of the aggregates with smaller sizes.