Formation of the Dynamic Clusters in Concentrated Lysozyme Protein Solutions

Neutron spin echo (NSE) and small angle neutron scattering (SANS) were used to investigate the correlation between structure and short-time dynamics of lysozyme solutions in the presence of protein clusters as previously reported. It was found that, upon increasing protein concentration, the. self-diffusion coefficient at the short time limit becomes much smaller than that of the corresponding hard-sphere and charged colloidal suspensions at the same volume fraction. Contrary to literature conclusions, we find that, at relatively low concentrations, the system consists mostly of monomers or dimers; while, at high concentrations, large dynamic clusters dominate. Our results will benefit the understanding of colloidal systems with both a short-range attraction and an electrostatic repulsion that are ubiquitous in many biologically relevant systems.