Protein Aggregation Studies Using PFG NMR Diffusion Measurements

摘要

The propensity of lysozyme to aggregate is well-known. The aggregation and crystallisation behaviours of lysozyme are closely linked as it has been reported that the critical nucleus most likely consists of four monomers and the growth unit is probably not the monomer but is more likely to be the octamer. The aggregation process has a complex dependence on pH, temperature and the protein and salt concentrations. This complex behaviour results from intermolecular forces since proteins are both colloids and polymers.~1 Lysozyme has an isoelectric point of pH 11 and thus at most pHs has a net positive charge. In low ionic strength solutions, ysozyme interacts mainly through a combination of electrostatic repulsion and attractive dispersion forces.~2 Addition of salt lowers the electrostatic barriers thereby achieving supersaturation of the protein at lower protein concentrations.