Afterwords, the only way I found to solve indirectly the problem was with command select @#/serialNumber=48727 which pointed to residue 3687.W with segname WT2 I hope there is a quicker way fp ---------- Forwarded message --------- From: Francesco Pietra <chiendarret@gmail.com> Date: Sun, Nov 15, 2020 at 11:03 AM Subject: zone & segname To: chimera <chimera-users@cgl.ucsf.edu> Hello Working with charmm36, therefore with the great aid of segname for my homotrimer, when commanding sel :27.M z<3 I get also a water molecule, with O-atom Tip3 3687.W OH2 Is there any way to extend the above command in order to have the segname associated with this water residue? This is because there are eight 3687.W residues with different segnames. I tried to solve indirectly the problem with sel :3687.W@/pdbSegment=WT# where # ranges from 1 to 8 (i.e., the same residue name for segname WT1 to WT8). Contrary to my expectations, it does not work The same with sel :3687@/pdbSegment=WT# Thanks for advice francesco pietra