Dear Martin,
a couple of years ago we had a similar problem with FAD degradation. In
our case it was not caused by radiation damage, but we saw different
ratios of intact and degraded FAD depending on the age of the crystals
[Winkler et al., Nat. Chem. Biol. 4, 739-741 (2008)].
Best regards,
Karl
Am 06.11.17 um 12:01 schrieb Martin Malý:
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
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Karl Gruber
Institute of Molecular Biosciences
University of Graz
Humboldtstrasse 50/3 e-mail: [email protected]
A-8010 Graz phone: (+43 316) 380-5417
AUSTRIA fax: (+43 316) 380-9897
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