Coherent Diffractive Imaging of Two and Three-Dimensional Membrane Protein Crystals using XFELs

• Rebecca Ryan (CXS University of Melbourne)
• Keith Nugent (CXS University of Melbourne)

The potential for imaging biomolecules using fourth generation XFEL sources is now being explored with the commisioning of beamline experiments having begun at the LCLS (Stanford). These experiments will employ the use of coherent X-ray diffractive imaging techniques by collecting snapshot diffraction patterns in a time regime that avoids nuclear damage in biomolecules. The opportunity to perform imaging of single biomolecules (such as membrane proteins) is present. Some membrane proteins form single two-dimensional crystals and submicron single three-dimensional crystals. Diffraction data collected from periodic samples (such as these small membrane protein crystals) will provide both an amplified intensity measurement and additional a priori constraints(the periodicity of the sample) that will benefit image reconstruction. We have simulated the diffractions produced using XFEL radiation for two-dimensional and three-dimensional submicron crystals of the membrane proteins lysozyme, potassium channels and bacteriorhodopsin for upcoming experiments. We seek to perform appropriate phase-retrieval on this data that will lead to high resolution solutions to membrane-protein structures.