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Phase Diagram Visualization Via Continuously-Fed Crystallization: Experiments and Model

Masano Sugiyama, Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, MN 55455 and Victor H. Barocas, Department of Biomedical Engineering, University of Minnesota, 312 Church St SE, 7-115 Hasselmo Hall, Minneapolis, MN 55455.

X-ray diffraction is the most common way to determine structural information of proteins at an atomic level. Elucidation of these structures has a dynamic impact on biotechnology and pharmacology. To determine the protein structure, a high-quality crystal of sufficient size is required. However, the production of such crystals is a current bottleneck. Current technology involves hundreds of conditions in this multi-parametric process to be tested by either batch or vapor diffusion crystallization techniques. Knowledge of the phase diagram allows experimenters to better design experiments to grow large high quality crystals.

A continuous-feed crystallization chamber is manufactured to allow phase diagram visualization to predict the phase diagram of a protein in a single experiment. This microfluidic system allows the experimenter to screen a large range of salt and protein concentrations by controlling the convection and diffusion of both protein and salt. A continuous-feed crystallization chamber has been successfully fabricated and characterized in terms of its flow profile. The protein and salt concentration profiles are determined using a computational model. Experimental results determine locations where crystals form and in combination allow determination of the phase diagram. This device has successfully predicted the well-known phase diagram for tetragonal lysozyme and has been utilized on triclinic lysozyme, a protein crystal for which the full phase diagram is unknown.