Hi Prathvi, All of the selected atoms are used as reference points (each is used individually, and results summed). The zone is based on all of the atoms that were selected at the time you used the tool. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Department of Pharmaceutical Chemistry University of California, San Francisco

On Nov 18, 2022, at 4:54 AM, Prathvi Singh via Chimera-users <chimera-users@cgl.ucsf.edu> wrote:

Elaine, In UCSF Chimera, when I try to find all the atoms within 4A of a selected residue using the Zone tool, it selects several atoms around that residue. However, I am not able to understand which atom of the selected residue was taken as the reference point for calculating the distances. Please help.