[phenixbb] phenix.xtriage says that entire res range contains anomalous signal but chart says differently?
Nathaniel Echols
NEchols at lbl.gov
Tue Aug 11 12:06:55 PDT 2009
On Aug 11, 2009, at 11:37 AM, sbiswas2 at ncsu.edu wrote:
> Is there a chance of backsoaking even when the protein has been
> expressed
> as a selenomethionine derivative? I just overexpressed the protein by
> shutting down the methionine biosynthesis in E.coli and incorporated
> SeMet
> instead of methionine.
> The protein has three methionine and is 26kDa
You could mass-spec the SeMet protein to make sure the expression
worked, but these protocols rarely fail. Assuming the incorporation
of SeMet is nearly complete, you'd see a huge fluorescence peak even
if the methionine sidechains were disordered. Especially if the
crystals diffract weakly and your overall signal-to-noise ratio is
relatively low, it's not terribly surprising that you don't have much
anomalous signal. I've seen lots of data like this (sometimes with
many more Met residues); unfortunately, I've never found any solution
other than growing better crystals. It might help to collect more
frames to improve the signal, but this is also going to increase the
radiation damage.
--------------------
Nathaniel Echols
Lawrence Berkeley Lab
510-486-5136
NEchols at lbl.gov
More information about the phenixbb
mailing list