Hi Eric, Thanks for your information! I tried the command, saved this gro to pdb file, opened new pdb, and it worked! BTW, it seems chimera cannot write new gro file (It can write these four files: 'pdb', 'pqr', 'mol2' or 'sph', but not gro) Could I ask you another question? In chimera I can manually change Carbon with 4 bonds to Nitrogen with 3 bonds using Tools/StructureEditing/BuildStructure/ModifyStructure. But I cannot find corresponding command line to do the same thing in chimera tutorial. So, is it possible that we can use command line to modify atom/element, its bonds and its geometry? Thanks! Best, Lei ________________________________ From: Eric Pettersen <pett@cgl.ucsf.edu> Sent: Tuesday, March 23, 2021 1:52 AM To: Lei Qian <tuk04130@temple.edu> Cc: chimera-users@cgl.ucsf.edu BB <chimera-users@cgl.ucsf.edu> Subject: [External] Re: [Chimera-users] [External] Re: in *.gro file, chimera takes CL atom as C (in compound) and gives it wrong color Hi Lei, If all your chlorine atom names start with the characters "CL", you can change them all to chlorine after you open the .gro file with this command (Favorites→Command Line): setattr a element Cl @CL= --Eric Eric Pettersen UCSF Computer Graphics Lab On Mar 21, 2021, at 7:54 PM, Lei Qian <tuk04130@temple.edu<mailto:tuk04130@temple.edu>> wrote: Hi Eric, Sorry for my late reply. Yes you are right. I tried it again: I made a new gro file containing only CL and K as ions, and opened it using chimera. I found chimera colored K as violet, which is good; but it colored CL as the same color as Carbon: yellow. Thank you again for your help! Best, Lei On Tue, Feb 23, 2021 at 5:04 AM Eric Pettersen <pett@cgl.ucsf.edu<mailto:pett@cgl.ucsf.edu>> wrote: Hi Lei, There is no explicit indication of the chemical element type in a .gro file, so it's all guesswork. Chimera assumes that atom names that begin with any of the letters C, O, P, S, H, or N are the corresponding single letter element type. This prevents atom names like CA and HG from being interpreted as calcium and mercury, rather than carbon and hydrogen. There aren't any great solutions. One option is to read in the .gro file, write it out as a .mol2 file, then edit that file to change the atom type of the CL atoms to Cl, then read that back in. Another is to select your CL atoms and use the "Modify Structure" tab of the Build Structure tool to change their element to Cl. --Eric Eric Pettersen UCSF Computer Graphics Lab On Feb 18, 2021, at 8:30 PM, Lei Qian <tuk04130@temple.edu<mailto:tuk04130@temple.edu>> wrote: Dear users, Could I ask a question on chimera? Thanks! I tried to open a gro file (small compound) using chimera. Like below: ... ... 1 LIG CL 18 x.xxx x.xxx x.xxx 1 LIG CL1 19 x.xxx x.xxx x.xxx ... ... Although chimera shows the CL name "CL" when the cursor is above the atom, but the CL atom color is incorrect: the same as Carbon. I tried to change the "CL" to "BR", and the chimera shows the correct color: dark red. It seems weird to me. Could you please give me any suggestions? Thanks! Best, Lei _______________________________________________ Chimera-users mailing list: Chimera-users@cgl.ucsf.edu<mailto:Chimera-users@cgl.ucsf.edu> Manage subscription: https://plato.cgl.ucsf.edu/mailman/listinfo/chimera-users _______________________________________________ Chimera-users mailing list: Chimera-users@cgl.ucsf.edu<mailto:Chimera-users@cgl.ucsf.edu> Manage subscription: https://plato.cgl.ucsf.edu/mailman/listinfo/chimera-users