Dear Sergei, It is difficult to say without looking at XDS or MOSFLM logfiles, but this sort of problem (high & flat Rsym in all resolution bins) sounds like the crystal vibrating wildly in the cryostream. You could ask the data collector the following questions: 1) Was the cryostream misaligned or too far from the sample? 2) Is the crystal mounted in a long & wobbly loop? 3) Was the incident beam varying (in XDS check the average background count for each image)? I wrote a web page to troubleshoot this sort of problem when I was beamline scientist on ID29 at the ESRF. Unfortunately the pages are no longer available, but I might have a backup if you are interested. Cheers, Bill
________________________________ De: CCP4 bulletin board de la part de Sergei Strelkov Date: ven. 05/11/2010 09:40 À: CCP4BB@JISCMAIL.AC.UK Objet : [ccp4bb] High Rmerge with thin frames Dear All, I am processing a dataset collected (not by me) with 0.1 degree oscillations. The diffraction is quite weak even though there is a clean diffraction pattern to about 3A. Either Mosflm or XDS processes the data readily with +/- default settings but both yield a high overall Rmerge of about 0.23 in the expected symmetry. Processing in P1 yields an overall Rmerge of ~0.18, but what is especially disappointing is that Rmerge is as high as 0.15 at ~5A resolution already. The question is, how can we process the data so that the merging statistics becomes more reasonable? Apparent mosaicity turns out to be ~0.5A. My naive way of thinking is to try treating each five consecutive frames as a single 0.5 degree frame. Does anyone have experience with this? Many thanks in advance, Sergei
