If your translational NCS is defined by a vector that does not correspond
to lattice centering, i.e. has numbers different from 0 or 0.5, this is
likely a case of order-disorder. Most such cases can be easily diagnosed
by abnormal patterns in spot shape, e.g. every second reflection has a
non-Bragg streak associated with it.
Apparent dense packing, 18% of the solvent, is likely to arise from random
packing of molecules in alternative positions within the unit cell, where
every second position is occupied. This randomness can be cross-correlated
between cells, and this will produce a diffuse scattering.
An alternative explanation is that you crystallised a proteolitic fragment
of your protein.
Zbyszek Otwinowski
> Dear all
> i have a small query to ask and seek your suggestions:
>
> I have collected a data for a protein with 324 residues and processed at
> its best in P212121. So Matthews suggest 1 mol in ASU with expected Mol.
> weight of 43 kDa with sovent content of 58% and 2 mol./ASU with 18%
> solvent
> content. However the data suggest possibility of translational NCS so i
> think i should ask for two molecules so that both get corrected for NCS.
> However for 2 mol./ASU, Matthewssuggests a total mol. weight of 52 kDa. So
> how to decide which way to proceed for MR?
>
> Thanks
> Monica
>
Zbyszek Otwinowski
UT Southwestern Medical Center at Dallas
5323 Harry Hines Blvd.
Dallas, TX 75390-8816
Tel. 214-645-6385
Fax. 214-645-6353