Mario,
As others have asked, why/how did you decide on P1? You mentioned
pseudo-translation being present. Depending on the location in the
Patterson map this could be a pseudo-centering operator showing an
apparent I4 space group. If this is the case you may want to reindex in
the P4 cell and try to solve it that way without the pseudo-centering,
especially if the off-origin Patterson peak is large (>50% of origin peak).
Jon Schuermann
--
Jonathan P. Schuermann, Ph. D.
Beamline Scientist
NE-CAT, Building 436E
Advanced Photon Source (APS)
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
On 09/30/2010 06:54 AM, Mario Milani wrote:
Dear all,
i have a 30 kDa protein that crystallize so far in three different conditions
but with the same space group. It initially looks like tetragonal (I4, a=141,
b=141, c=208) and then results triclinic (P1, a=141, b=141 c=144, alpha=119,
beta=119, gamma=90), hosting about 24 mol. in the unit cell. Other data: self
rotation shows the presence of 4 peaks with chi=180; molecular replacement
shows the presence of a pseudo-translation peak; DLS made at protein
concentration close to crystal growth conditions shows a Rh compatible with
something like a tetramer with low polydispersity (about 15%). Do you have any
experience with similar ‘asymmetric’ associations? Do you have any suggestions,
beside the addition of ligands to the crystal growth conditions, in order to
get a ‘simpler’ crystallographic assembly? I have some models (with sequence
identity less than 25%) in order to try MR but all trials so far did not solve
the structure (using balbes, molrep, phaser and epmr). Any suggestion is
welcome.
Thank you,
Mario Milani
--
Jonathan P. Schuermann, Ph. D.
Beamline Scientist
NE-CAT, Building 436E
Advanced Photon Source (APS)
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
email: schue...@anl.gov
Tel: (630) 252-0682
Fax: (630) 252-0687
