Hi, I'm trying to do a mixed individual isotropic anisotropic refinement b factor refinement and can't get my atom selections to be accepted by phenix.refine. For the atoms I want to do isotropic refinement I used optional (element H or element D or resname HOH or chain E or chain F or chain A or chain B) for the anisotropic selection I used chain A and chain B and not (element H or element D or resname HOH or chain E or chain F or chain A resseq 5:11 or chain A resseq 66:72 or chain A resseq 117:138 or chain A resseq 152:184 or chain A resseq 196:210 or chain A resseq 249:251 or chain B resseq 3:6 or chain B resseq 66:72 or chain B resseq 166:210 or chain B resseq 249:251) I've tried various combuinations, but so far all have given the error message: Selection string results in empty selection. Thanks for your help Mark --