Dear Martin,
A more bleeding-edge type of experiment in the vein David is
indicating would be to use a "rotation SFX" protocol to record
complete data off one or very few crystals that will be completely
exempt from radiation damage, as described in doi:10.1038/nmeth.2962
and in doi: 10.1073/pnas.1418733111 .
Good luck!
Gerard
--
On Mon, Nov 06, 2017 at 08:07:40AM -0500, David Schuller wrote:
> Some alternative interpretations have been suggested, but if you think you
> are seeing radiation damage, you could try collecting data on several
> crystals and binning it by dose received. For comparison see:
>
>
> The catalytic pathway of horseradish peroxidase at high resolution.
> Berglund, et al. (23 May, 2002) Nature 417(6887), 463-8
> DOI:
> 10.1038/417463a <https://doi.org/10.1038/417463a>
>
>
> If your low dose and high dose structures appear nearly the same, then you
> are seeing something other than radiation damage.
>
>
>
> On 11/06/17 06:01, Martin Malý wrote:
> > 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
>
>
> --
> =======================================================================
> All Things Serve the Beam
> =======================================================================
> David J. Schuller
> modern man in a post-modern world
> MacCHESS, Cornell University
> schul...@cornell.edu
>
