Hello: I need to change several histidine residues (both HIS and HIE, although both called HIS) to HIP. I tried manually. In case of monoprotonation at NE2: modify structure element N bonds 3 geom trigonal connect to preex atoms color by element change modified residue's name to HIP set atom names to ND1 or retain current atom names In both cases the proton attached to ND1 takes the name "H1" instead of the expected HD1. Is that error in the above procedure or chimera bug? (chimera alpha version 1.5 (build 30702) on GNU/LINUX 32bit) Addendum: is there any other method of accomplishing the task with chimera? It is rather troublesome to go through all monoprotonated histidines of this large homomer (in different chains HIS of the same number have been differently protonated by reduce). A problem with reduce (if not my misuse of reduce) is that all histidines become monoprotonated, while the experimental pH is such that all should be diprotonated. I must add that I am bound to reduce because the program that I use subsequently goes through reduce. thanks for help francesco pietra