What are your cell constants and space group? It sounds to me you misindexed and then artificially "twinned" your structure by integrating/merging in too high of a symmetry. I've seen that happen for primitive hexagonal which was actually C-centered monoclinic. Also, in my experience this is more likely to happen with denzo/scalepack as it refines every image and does postrefinement in scalepack. XDS will decide for you on a symmetry after integration, and in MOSFLM you should see earlier that something is wrong.
HTH Jens On Wed, 2012-01-04 at 21:42 +0800, Zhiyi Wei wrote: > Dear all, > > I recently collected a dataset (~2000 frames) from a single crystal. > If merge first 600 frames (sca1) or last 600 frames (sca2), Rmerge > values from scalepack seem to be ok (~10%) though rejection ratios are > high (~5%). But if I merge all frames together, Rmerge value goes up > to ~20% and rejection is extremely high (~20%). Then, I checked sca1 > and sca2 by xtriage in phenix. Surprisingly, the logfiles told me that > sca1 is no twining while sca2 is very likely to be twinned. I never > met this case before. So, I am wondering if it is possible from a > non-twinned structure to a twinned structure just due to radiation > damage. If the answer is yes, does it mean that I should not collect a > large number of frames to amplify anomalous signals by using this > crystal? > > Thanks a lot! > > Best, > Zhiyi
