CHAPTER 2: Imaging Protein Dynamics by XFELs

The advances, opportunities and challenges during the first 7 years of structural biology using X-ray lasers are reviewed and their historical context provided. The main focus is on the achievements and prospects for imaging protein dynamics at near-atomic spatial resolution under native and controlled chemical conditions, and a summary of the many approaches to this aim is given. Radiation damage, comparisons of XFEL and synchrotron work, single particle diffraction, fast solution scattering, pump-probe studies on photosensitive proteins, mixing jets, caged molecules, pH jump and other reaction initiation methods, and the thermodynamics of molecular machines are all discussed, in addition to data analysis methods for all the instrumental modes. The ability of the XFEL to separate chemical reaction effects in dynamical imaging from radiation-induced effects (by minimizing these), while imaging at physiological temperatures and in the correct heat bath required for molecular machines is highlighted.