Lysozyme Aggregation Studied by Light Scattering. I. Influence of Concentration and Nature of Electrolytes

Static and dynamic light scattering have been employed to investigate the behaviour of lysozyme solutions when varying the concentration of (NH₄)₂SO₄ and NaCl for screening the repulsive forces between the monomers. At the initial aggregation stages clusters, which can be classified as mass-fractals undergoing diffusion limited-like aggregation, coexist with monomers or small lysozyme oligomers. The kinetics of fractal growth deliver observables that exhibit distinct tendencies when examined as a function of the concentration and nature of the electrolyte. The behaviour of the observables changes drastically above 0.84 M (NH₄)₂SO₄ and 0.60 M NaCl. Static light scattering revealed a progressive restructuring of the fractals to compact structures at the latter stages of the reaction. Based on the correlations between the various observables an attempt is made to predict the long-term fate of the nucleating solutions.