I see that phenix is using the same kind of simplistic statistical restraints as CCP4. Are there plans to improve the geometry restraints once the rest of phenix is stable? The problem with simple statistical restraints as used by CCP4 is that they completely ignore correlations due to interactions of multiple restraints. This is particularly bad for puckered rings like proline and nucleic acids. Nucleic acids get around this by using a fixed sugar pucker, which results in a lot of bad geometries for non-helical nucleic acids (many of which make it in to the PDB). However, if you consider the geometries "ideal value" and "ideal value esd" as just another way to write a harmonic restraint, then it is possible to make an improved restraint library. In this case, some individual geometry restraints will have target values that restrain towards non-ideal values in order to produce the correct result when all terms are combined. The problem is that these terms will give higher RMSD values, which would probably confuse software like REFMAC, which is designed to tweak restraint weights based on RMSDs. So, does phenix have any built-in restraint adjustments that is based on current rmsds? If so, is there a way to disable it? Joe Krahn