> Rsym is 0.6 I'd be seriously worried about this. An R-sym value of 0.6 in the entire resolution range (I assume) means that your reflection intensities do not match. This is the value of the Rsym I could expect in the high resolution bin - in the age of maximum likelihood refinement, not in the entire resolution range.
Further, if your space group is P2 or P2(1), then you must reindex your initial data set so that what is currently the alpha angle becomes the beta angle. And then perform the molecular replacement searches. The values you give for the beta and gamma angles are suspiciously close to 90 degrees (although it can be possible to have P1 with angles suspiciously close to 90 degrees). Fred. > Message du 12/07/10 05:10 > De : "孙庆祥" > A : CCP4BB@JISCMAIL.AC.UK > Copie à : > Objet : [ccp4bb] A strange case of MR > > Dear ccp4 experts, > > I'm a beginner and have a problem with the following structure solution. I > need great help from you experts. Thanks in advance! > > The dataset is 1.6A resolution and the spots looks ok, except some smear in > the higher resolution. Space group is P1(could be P2 or P21). Completness is above 95% and mosaicity is less than 1. Rsym is 0.6. > > Cell parameters are: a=18.2320 b= 39.6330 c=77.5260 alpha=104.8230 > beta=90.0780 gamma=90.0400 > > The model is about 60 amino acids snake venom protein with 60% identity. > However, no solution with an initiall R less than 0.7 was obtained by Molrep, Phaser, or Phenix . > > Using a molrep search result (R=0.75, mtz in P1, 2 moelcules in AU), with > Refmac5 twin refinement, we could refine the structure to 40% Rfree and 38%Rwork. The density looks good (can see hole in rings structures) for all residues and no continous unexplained density is observed. However, the R and Rfree does not go down no matter what we try... > > We tested the twinning by CNS or the crystal twinning server > (http://nihserver.mbi.ucla.edu/Twinning/) and found no twinning present. > > I'm sure the sequence is correct. > > I've tried hard on this for quite some time. Really appreciate if you could > help. > > Thanks and regards, > > Jeremy
