Hi Yu,

Have you tried using the Additive Screen (e.g. from Hampton Research) on
top of your crystallization condition, and varying the ratio between
protein complex and crystallization solution? From the diffraction pattern,
it looks you are almost there. Salt crystals don't show spots close to the
beam stop usually, so the chance of them being salt crystals is negligible.
A little bit of tweaking in crystallization conditions should do the trick.
If all this fails, probably, you will have to remove any floppy ends from
the proteins in the new constructs.
I had a similar experience where the protein with His-tag showed crystals
in a lot of conditions but all spherical and cylindrical crystals
diffracting to 3.5 A. The protein after removing the His-tag gave crystals
that diffracted to 2.4 A.

Good luck!

On Tue, Feb 13, 2018 at 9:09 AM, Yu Qiu <yu....@sanofi.com> wrote:

> Hi,
> I have been trying to crystallize a protein complex and keep getting
> sphere shape crystals. The diffraction is around 3 angstrom, but looks like
> multiple lattices. I am wondering if it could be a quasi crystal? Is there
> anyone has such experience?
> Thanks,
> Yu

Gyanendra Kumar, PhD
Associate Scientist,
St. Jude Children's Research Hospital,
Department of Structural Biology,
262, Danny Thomas Place, MS-311
Memphis, TN 38105
Cell: 631-875-9189

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