[phenixbb] Molecular replacement at low resolution

[Roger Rowlett]

Before giving up, search in all 8 possible P422 space groups, individually
if necessary. You may have to relax or eliminate packing restraints to get
solutions or partial solutions to inspect. Looking at packing of these
solutions may give you some clues about the true number of molecules in the
ASU and eliminate dome space groups. Matthews calculations are not terribly
reliable for N>2. Treat your 8 as a very rough estimate.

If Phaser doesn't work, try EPMR. Ultimately, you may not have sufficient
data, but we just solved a difficult data set in P222 point group at 3.4 A
with N=6, (Matthews predicted N=8). Looking at packing in Coot suggested a
packing problem where a tetramer straddled one of the 2 fold axes.
Searching for 3 dimers worked nicely.

__________________
Roger Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
On May 2, 2015 11:01 AM, "mohamed noor" <mohamed.noor34 at gmail.com> wrote:

> Dear developers
>
> I have a dataset to about 4 A in point group P 4 2 2 (Pointless suggests P
> 41 21 2). The protein is about 11 kDa and has an identity of about 50 % to
> my search model. Phaser calculated the eLLG to be about 5, and maybe not
> surprisingly, it failed even after using Sculptor to prepare the model.
>
> It also says that solutions with Z-scores more than 8 were rejected for
> failing the packing test. Are there any suggestions on getting a solution?
>
> Solvent content calculation from Xtriage suggests about 8 copies in the
> asu. Would this be of any help in MR?
>
> Thanks.
>
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