[ccp4bb]: GFP losing coloration in X-ray beam?

[Artem Evdokimov]

Hello fellow ccp4-ers,   Here’s a somewhat unrelated question J   We’ve recently solved a structure of a green fluorescent protein from a marine copepod Pontellina plumata (PDBIDs 2G6X, 2G6Y – already released to the public), and are in the process of publishing the results. While I was collecting data (100K), I have noticed a peculiar phenomenon: during the very first X-ray exposure, the normally intensely greenish-yellow color of the crystals completely disappeared within the area that was hit by the beam. That was happening in real time, while the crystal was still frozen. There was no significant deterioration of diffraction quality, and the structures were successfully solved using these data. We noted no anomalies in the chromophore as such – it looks like a typical GFP heterocycle, although the resolution isn’t sufficient to refine w/o restraints and thus verify the exact bond types etc.   Here’s the question – does anyone know of a published report of this phenomenon, as related to other GFPs, or other colored/fluorescent beta-barrel proteins? We couldn’t find any, but that doesn’t mean that there wasn’t a mention in one of the dozens of GFP structural papers.   Thank you,   Artem   [EMAIL PROTECTED] ex-PGP