A Plug-Based Microfluidic System for the Crystallization of Proteins

Cory Gerdts, University of Chicago, speaking at Advances in Protein Crystallography 2007.

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Abstract
A Plug-Based Microfluidic System for the Crystallization of ProteinsProtein crystallization remains a bottleneck in the process of elucidating structural information from proteins. We will discuss a plug-based microfluidic system that has been recently developed for the crystallization of proteins.

This system isolates protein crystallization trials into ~20 nL-sized droplets (plugs), surrounded by fluorinated carrier fluid in microfluidic capillaries. Both sparse matrix and gradient (optimization) screening are performed using this system. Sparse matrix screening is performed by fabricating pre-formed cartridges of reagents and merging them with the protein stream.

Gradient screening is performed simply by varying the flow rates of the precipitants being used. Once crystals are obtained, they can be removed from the capillary for cryoprotection or examined at room temperature in situ. We will describe an inexpensive and user-friendly system capable of screening multiple precipitants at many concentrations.

We will also discuss new aspects of the microfluidic system that allow us to better control and understand nucleation of protein crystals, such as the effect of mixing on nucleation and a technique for microfluidic seeding, which we have used to solve the structure of the novel protein, Oligoendopeptidase F.