Mike,
You could try rigid body refinement against the weak reflections to
get the position of the molecules right and then normal restrained
refinement against the strong reflections. I had a case like this some
years ago and that helped...
Esko
On 17.10.2010, at 6.48, Mike John wrote:
>
>
> Hi all,
> The data is 2.2A, p41212, unit cell has c axis twice longer than a
> or b. Data processed by HKL2000, the diffraction pattern shows
> Strong-weak-weak in C direction, indicating translational pseudo-
> symmetry.
> Xtriage analysis confirmed the pseudo-symmetry (large Patterson off-
> origin peak).
> The model is 100% identical searching prob.
> Phaser MR solved the structure easily with good Z-score and LLG(3
> copies/a.u). The problem comes during the refinement:
> The R-free converged around 50% (R-factor 38%) and never go down
> even though I tried hard including, twin possibility.
> Seeking help to lower the R-free. Thank you very much
> Mike
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