Light scattering investigations of protein and virus crystal growth: ferritin, apoferritin and satellite tobacco mosaic virus

Abstract

Quasi-elastic light scattering was used to investigate the nucleation and crystallization of apoferritin, ferritin and satellite tobacco mosaic virus (STMV). Supersaturation dependent critical nuclear size supportive of stable macromolecular crystal growth was estimated to be in the range of 5 to 65 monomer protein and virus particles. The interfacial free energy and the activation energy for apoferritin crystal growth was estimated to be 2.7 x 10-2 erg/cm2 and 8.5 kcal/mol, and for STMV 1.8 x 10-2 erg/cm2 and 10 kcal/mol, respectively. The data suggests that the rate limiting factor in STMV crystal growth is the diffusion of virus clusters to the growing crystal nucleus, while apoferritin crystallization is limited by surface kinetics. The aggregation rate is substantially higher for crystallization with a power law exponent of n = 0.33-0.54 (STMV) and n = 0.8-1.0 (apoferritin), while that associated with eventual amorphous precipitate was n = 0.20.