All I had a structure that seemed perfectly twinned in P41 21 2, completely built to the observable density (no peaks in 2Fo-Fc map over 2sigma) and refined to 33/35 (R/Rfree). I indexed, scaled, and merged the original unmerged data to P41, molecular replaced using the above model. Three rounds of rigid body refinement of the MR solution with group adp's dropped R/Rfree to 28/30 (while generating new free R flags based on the P41 data). The resolution was to 2.5 so I skipped the NCS. Now I try to do a second round of refinement with this time individual_sites and individual_adps with no change to the input model. The final R/Rfree's are now in the 50's? Am I missing something (fundamental) ? Thanks FR --------------------------------------------- Francis Reyes M.Sc. 215 UCB University of Colorado at Boulder gpg --keyserver pgp.mit.edu --recv-keys 67BA8D5D 8AE2 F2F4 90F7 9640 28BC 686F 78FD 6669 67BA 8D5D