A crystalline sample of CrLOV1 was optimized for serial crystallography. Time-resolved serial synchrotron crystallography provides high-resolution insights into structural changes of CrLOV1 from Δt = 2.5 ms up to Δt = 95 ms post-photoactivation, resolving the geometry of the thio­ether adduct and alteration of the C-terminal region implicated in the signal transduction.

The photo-reaction of the LOV1 domain of the Chlamydomonas reinhardtii phototropin is investigated by room-temperature time-resolved serial crystallography. A covalent adduct forms between the C4a atom of the central flavin-mononucleotide chromophore and a protein cysteine. The structure of the adduct is very similar to that of LOV2 determined 23 years ago from the maidenhair fern Phy3.