Crystal structures have provided detailed insight in the architecture of rhodopsin photoreceptors. Of particular interest are the protein-chromophore interactions that govern the light-induced retinal isomerization and ultimately induce the large structural changes important for the various biological functions of the family. The reaction intermediates occurring along the rhodopsin photocycle have vastly differing lifetimes, from hundreds of femtoseconds to milliseconds. Detailed insight at high spatial and temporal resolution can be obtained by time-resolved crystallography using pump-probe approaches at X-ray free-electron lasers. Alternatively, cryotrapping approaches can be used. Both the approaches are described, including illumination and sample delivery. The importance of appropriate photoexcitation avoiding multiphoton absorption is stressed.
Keywords: Nanocrystallography; Photoexcitation; Pump probe experiment; Retinal; Rhodopsin; SFX; Serial crystallography; Serial femtosecond crystallography; Time-resolved crystallography; X-ray free-electron laser; XFEL.
© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.