I don't know why that doesn't work, but: select :WAT@O seems to (if you only have the one water in your pdb file), as does: select :127.water@O (which would presumably limit the selection to the one water molecule) - Mark ________________________________ From: chimera-users-bounces@cgl.ucsf.edu [chimera-users-bounces@cgl.ucsf.edu] on behalf of George Tzotzos [gtzotzos@me.com] Sent: Thursday, November 14, 2013 8:08 AM To: chimera List Subject: [Chimera-users] Residue selection I'm attaching a pdb file of a protein ligand complex with a single conserve water molecule. The pdb file was constructed with Antechamber Leap. The water molecule is numbered as residue 127. When I try to select using: select :127 nothing happens. Selection works with: select :WAT The problem is that I need to monitor the distance between :127@O and a particular atom in the binding site of the protein during an MD trajectory. My question is if I'm doing something wrong with the residue selection. Many thanks in advance for your help Regards George _______________________________________________ Chimera-users mailing list Chimera-users@cgl.ucsf.edu http://plato.cgl.ucsf.edu/mailman/listinfo/chimera-users