(88b) X-Ray Compatible Microfluidic Platforms for in Meso Crystallization of Membrane Proteins

Membrane proteins play a crucial role in many important biological processes including energy and material transduction across cellular membranes, molecular recognition and immune response. They are amphiphilic in nature and extremely sensitive to the surrounding environment. Efforts to understand the function of these proteins have been hampered by difficulty in obtaining high quality crystals. In meso membrane protein crystallization [1] is a recently developed technique which uses lipids to create a membrane like environment in which proteins are stabilized. We created microfluidic chips that are able to create these mesophases by mixing highly viscous lipids with aqueous protein solutions. Addition of salt results in phase transformation triggering crystal nucleation and growth. We have validated these polydimethylsiloxane (PDMS) based microfluidic chips using Bacteriorhodopsin [2]. However PDMS attenuates X-rays, so on chip analysis of the crystals formed is not feasible.

Here we present an X-ray compatible platform comprised of cyclic olefin copolymer (COC) and a thin PDMS membrane needed for valve actuation. As proof of concept we have crystallized and obtained a full data set for soluble proteins on-chip. Presently we are validating this platform for the crystallization of membrane proteins, followed by on-chip X-ray analysis. Furthermore, we plan on using the platform to study the phase behavior of lipids to further unravel the mechanism of in meso membrane protein crystallization.

1. Cherezov V. et al., 2007, Science, 318, 1258?1265 2. Perry S.L. et al., 2010, CG&D, 9, 2566?2569