[phenixbb] Difficult dataset and refinement--P422? I422?Twinning?

[Nathaniel Echols]

On Mon, May 7, 2012 at 8:46 AM, Kelly Daughtry <kddaught at bu.edu> wrote:
> Looking at the P422 data, it look like you have pseudo translational symmetry.
> Did you try processing this data as I422?
>
> From the P422_xtriage.log:
>
> The full list of Patterson peaks is:
>
>   x      y      z            height   p-value(height)
> ( 0.500, 0.500, 0.165 ) :   78.635   (6.634e-07)
> ( 0.000, 0.000, 0.330 ) :   56.292   (2.795e-05)
> ( 0.500, 0.500, 0.497 ) :   30.920   (1.207e-03)

One word of caution: an exceptionally high off-origin peak can mean
that the unit cell was measured too large, and you've integrated extra
reflections that are really non-existent.  (I'm not sure what the
threshold for this is, but 80% seems pretty large.)  Splitting and
various indexing artifacts can sometimes lead to this.  I'd recommend
running labelit.index on the images and seeing what it thinks the
lattice should be.

-Nat