Yu,
There is a parity analysis in dataman (a USF program) for example.
You have to take into account that the sigmas are generally estimated
assuming a unimodal intensity distribution, which is no longer true in
the pseudo-symmetric case. In practice this means that the sigmas of
the strong reflections tend to be underestimated (generally not a
problem really) and those of the weak reflections are overestimated.
This can be avoided to some extent by scaling the h+k = 2n and h+k = 2n
+1 reflections separately. I ended up writing a small python script to
do this from XDS output and scaling separately (see Oksanen et al.
(2006) Acta Cryst. D62 1369-1374). Of course it would be even better
if the scaling program would directly take into account the bimodal
distribution...
HTH,
Esko
On 26.7.2011, at 15.51, zhang yu wrote:
Hi,
I had a dataset which is P21 but with a pseudo-translational
symmetry of (1/2, 1/2 ,0). Theoretically the dataset should show
systematic weak spots of h+K= 2n+1 compared to h+k= 2n. Is that
correct?
I would like to have a close look at the reflections. for example,
the average I/sigma for reflections with h+k=2n+1 and reflections
with h+k=2n. Which software could do this job? A brief tutorial is
appreciated.
Yu
--
Yu Zhang
HHMI associate
Waksman Institute, Rutgers University
190 Frelinghuysen Rd.
Piscataway, NJ, 08904
Esko Oksanen, PhD
Post-doctoral Fellow (EMBO)
Groupe Synchrotron, Institut de Biologie Structurale J.P. Ebel
41, rue Jules Horowitz
F-38027 GRENOBLE Cedex 1
FRANCE
tel. +33 4 38 78 95 96
mob. +33 6 84 15 14 88
