Dear colleagues, I am investigating a structure of a FAD-dependent enzyme. The electron density map suggests radiation damage to the FAD. It apparently is different from simple change of the redox state and "butterfly"-like structure. We did not find in literature possible products of radiation damage, like a removal of several atoms of the FAD. Has anyone observed such effect?
To describe it in more detail, I can observe negative difference map of C2, N3, C4, and O4 atoms of flavine. Moreover, there is positive difference map close to O2 and O4 atoms thus it looks as water molecules are bound there instead of the missing FAD atoms. I am attaching parameters of the experiment: performed at synchrotron, exposition time 210 s, high resolution diffraction limit 1.65 A (<I/sigma> = 2 at shell 1.75-1.65 A). We could see a decrease of diffraction data statistics during the experiment hence we think there is significant radiation damage to the crystal. Thank you very much for ideas. Regards, Martin Maly
