MICROCALORIMETRIC AND SMALL-ANGLE LIGHT-SCATTERING-STUDIES ON NUCLEATING LYSOZYME SOLUTIONS

We have investigated the properties of nucleating lysozyme solutions, at various lysozyme and NaCl concentrations at pH 4.2, by isothermal c onduction microcalorimetry and small-angle static light scattering. Bo th types of experiments were performed under stirring and differ drast ically from their counterparts where stirring was not applied. Pronoun ced heat-power peaks, that can be attributed to nucleation and growth, appeal at finite times which in turn depend on the supersaturation le vel. The calorimetric results are in qualitative accordance with the n ucleation behavior deduced from small-angle scattering experiments. Th e implications of these experiments in the nucleation process of lysoz yme are (i) without stirring, large fractal clusters with dimensionali ties lower than similar to 2.00 farm and, after 1-2 days, large crysta ls appear and (ii) with stirring, nuclei of several micrometers in siz e appear within 2-13 h depending on conditions. Their dimensionalities -vary between 2.5 and 3.0, indicating dense morphology; their appearan ce is accompanied by showers of microcrystals.