Dear Martin, we experienced the butterfly-like structure of FAD in monoamine oxidases but this was observed also in other flavoenzymes. Whether this is an intrinsic feature of these enzymes or something due to radation damage is not clear for each case. However, in our experience this bent conformation was not accompanied by lack of density for FAD atoms (i.e. the cofactor was fully visible). So what you observed might actually be due to degradation rather than radiation damage.
Best Claudia 2017-11-06 12:01 GMT+01:00 Martin Malý <[email protected]>: > 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 > > -- Claudia Binda University of Pavia Dept. Biology and Biotechnology via Ferrata 1, 27100 Pavia - Italy Phone: +39-0382-985535 Fax: +39-0382-528496 E-mail: [email protected] Web: http://www.unipv.it/biocry
