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Nucleation precursors and the birth of crystals Host Publication: 15th International Conference on the Crystallization of Biological Macromolecules Authors: D. Maes, M. Sleutel, A. Van Driessche, M. Giglio, M. Potenza, T. Sanvito, J. Stiens, Y. Zhang, M. Vorontsova and P. Vekilov Publication Date: Sep. 2014
Abstract: Nucleation of crystals is one of the most secretive processes in chemistry, materials science, and biophysics. The two-step mechanism of nucleation was first put forward for protein crystallization and subsequently its applicability was demonstrated for colloids, small-molecule organic and inorganic substances, and polymers. The nucleation precursors are liquid-like protein rich clusters with a size that varies from under one hundred to several hundred nanometers. The mesoscopic clusters exist with similar characteristics both in the homogeneous region of the phase diagram of the protein solution (where no condensed phases, liquid or solid, are stable or present as long-lived metastable domains) and under conditions supersaturated with respect to the ordered solid phase.
In this lecture we will first focus on the characteristics of the nucleation precursors and their role in the nucleation process. Experiments show that the presence of clusters has a large effect on crystal nucleation. Clusters exhibit an Ostwald ripening behavior during a crystallization cycle. With Brownian Microscopy, previously used to study the dynamics of the clusters as a whole, we obtained information on the dynamics within the clusters. Furthermore our experiments revealed that the assimilation of clusters by the growing crystals can trigger a self-purification cascade of impurity-poisoned crystal surfaces. Finally we will report on our endeavors to capture crystals at birth with more novel techniques such as 'polarized Brownian Microscopy', Confocal Depolarized Dynamic Light Scattering and TeraHertz spectroscopy.
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