Imaging Ultrafast Single Particle Macromolecular Dynamics with X-ray Lasers

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Conformational dynamics are crucial for the functioning of most macromolecules and a deeper understanding of these motions holds great promise for future discoveries in biology. But it is difficult to probe the structure of macromolecules away from their most stable conformations, and time-resolved studies remain limited by the available techniques. Today a new generation of XFELs is growing. The extremely short pulse duration, high pulse intensity and repetition rate of these lasers offer new research opportunities in physics, chemistry, and biology. Since the first XFELs were proposed, the idea of obtaining images of individual proteins frozen in time has fascinated and inspired many, and we have been at the forefront of this quest. The combination of advances in XFEL technology with ESI has brought the dream of imaging hydrated single proteins by X-ray diffraction within reach. Currently time-resolved studies in solution in the sub-ms range are done through solution X-ray scattering or spectroscopic methods, but they can only provide limited structural information. XFELs provide a way to dramatically improve our understanding of these time-scales. This proposal aims to develop the science and technology to make ultrafast single-protein imaging a reality, through a three-step approach: (I) develop diagnostics suitable for nanosized samples, (II) enable single protein X-ray diffraction imaging through new sample delivery instrumentation, (III) perform time-resolved single protein imaging experiments using the unexplored tender X-ray energy range. Ultrafast imaging of macromolecules will reveal new horizons. As a single-molecule method with high time-resolution, it enables imaging the structural changes associated with fundamental processes such as enzyme catalysis, allosteric signal transduction or even protein folding. It also opens a way to record molecular movies and mapping the conformational landscape of isolated macromolecules for the first time.