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Abstract
Serial femtosecond crystallography using ultrashort pulses from x-ray free electron lasers (XFELs) enables studies of the light-triggered dynamics of biomolecules. We used microcrystals of photoactive yellow protein (a bacterial blue light photoreceptor) as a model system and obtained high-resolution, time-resolved difference electron density maps of excellent quality with strong features; these allowed the determination of structures of reaction intermediates to a resolution of 1.6 angstroms. Our results open the way to the study of reversible and nonreversible biological reactions on time scales as short as femtoseconds under conditions that maximize the extent of reaction initiation throughout the crystal.
Watching a protein molecule in motion
X-ray crystallography has yielded beautiful high-resolution images that give insight into how proteins function. However, these represent static snapshots of what are often dynamic processes. For photosensitive molecules, time-resolved crystallography at a traditional synchrotron source provides a method to follow structural changes with a time resolution of about 100 ps. X-ray free electron lasers (XFELs) open the possibility of performing time-resolved experiments on time scales as short as femtoseconds. Tenboer et al. used XFELs to study the light-triggered dynamics of photoactive yellow protein. Electron density maps of high quality were obtained 10 ns and 1 µs after initiating the reaction. At 1 µs, two intermediates revealed previously unidentified structural changes.
Science, this issue p. 1242
