Dear all, I am refining my structures at 2.5 A. The model is well fitting in the electron density. I already add water and ligands. I’m trying these options (XYZ coordinates, real-space, TLS parameters, Individual B-factors, Optimize X-ray/stereochemistry weight, Optimize X-ray/ ADP weight, Reference model restraints, Use secondary structure restraints, Simulated annealing (Cartesian), Automatically correct N/Q/H errors) to refine the structure but the R-free still be high. The reference model is 98% identity with the structure that I’m building. After refining, the R-work always decrease while R-free increase. My last values for R-work is 0.2501 and for R-free is 0.3246. I’m lost and don’t know what to try more. Can anyone could explain me what happens here ? What others options that I could use to optimize R-free value ? Thank you in advance ! Hang Pham ------------------------------------------------------ Hang Pham, Ph.D Student, The Doucet Lab Centre Armand-Frappier Santé Biotechnologie Institut National de la Recherche Scientifique (INRS) Université du Québec Réseau International des Instituts Pasteur 531 Boulevard des Prairies Laval (Québec) H7V 1B7 CANADA Téléphone : (450) 687-5010, poste 4210 Site web: http://www.profs.inrs.ca/ndoucet/