Aggregation of aqueous lysozyme solutions followed by dynamic light scattering and 1H NMR spectroscopy

In the presented work, we followed our previous calorimetric investigation [J. Poznaǹski, M. Wszelaka-Rylik, W. Zielenkiewicz, Termochim. Acta 409 (2004) 25-32], analyzing the kinetics of NaCl-induced lysozyme aggregation. The aggregates' size distribution was monitored independently by dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). Experiments were conducted for 2.1 mM lysozyme solution in acetate buffer, pH=4.25, in the NaCl concentration ranging from 0 up to 0.7 M. In order to maximize the reproducibility, both DLS and NMR experiments were run with the same lysozyme preparation coming from one lot. DLS experiments showed a systematical increase of the aggregates size, while upon NMR diffusion-ordered spectroscopy (DOSY) experiment in the hour time scale, no significant changes of the diffusion coefficient were observed. After ∼70 h of NMR experiment, 2.1 mM lysozyme solution in 0.5 M NaCl solution started to crystallize/aggregate, which was indicated by a decrease of both translational and rotational diffusion coefficients.