MOLECULAR AGGREGATION AND INDUCED NUCLEATION IN PROTEIN CRYSTAL GROWTH

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This research project aimed at analyzing kinetic mechanisms in induced nucleation during the processes of protein crystal growth, mainly using dynamic light scattering techniques and crossed Nicols method. The protein molecules dealt with in the present work were lysozyme and taka-amylase.The results obtained for lysozyme crystallization using the crusaded-Nicols method are summarized in the following ; (1) the induction times were obtained by measuring the duration for the occurrence of crystals in varying supersaturating values, (2) interface energies (gamma) were evaluated from the calculation of the induction times, whose inverse values are proportional to the rates of nucleation, and supersaturation, (3) the gamma values (erg/cm^2) were 0.3 both for sitting and hanging drop methods for crystallization, (4) micro-seeding effects were found to be dependent on the sizes of seed crystals and supersaturations.The results obtained for taka-amylase crystallization are summarized in the following ; (1) diffusion constants and average particle sizes increased quite abruptly after certain induction times in supersaturated solution, (2) the occurrence of this cahnges was prompted with increasing supersaturation values, and followed by the appearance of crystals detectable by naked eyes. Therefore, one may concluded that the molecular clustering of taka-amylase was formed in prior to nucleation, as detected by the dynamic light scattering technique.These results available for the two types of proteins have shown that the pre-nucleation events are detectable, in case that the molecular weights are as large as in taka-amylase. However, more precise experiments are not possible, because the fundamental data of solubility are lacking. Thus, the solubility of taka-amylase is now measured by using a two-beam interferometric method.