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.