Dear all,
I am refining a 1.4 A resolution structure and found some well-defined
but unfortunately unexplained density. The protein was purified in HEPES
buffer with PMSF and protease inhibitor cocktail tablets (Roche) added.
It was cocrystallized with AMPPNP in PEG2000MME and Tris. I modelled a
molecule into the density, which fits quite well but I do not know what
it is and how it got there. Attached are two pictures with the
difference density and the molecule I modelled in there.
Has anybody seen something like this before? Maybe some degradation
product of the buffer/PMSF?
Any suggestions will be highly welcome.
Thanks a lot
Annemarie
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