Dear All, I have a question regarding the contact interactions between a protein-ligand complex. I can retrieve the contacts by the findclash command in --nogui mode as below: chimera --nogui protligcomplex.pdb clash.com and similarly I can find the hbonds. The output I am getting is as below: -------------------------------------------------------------------------------- 32 contacts atom1 atom2 overlap distance LIG 1 H ALA 265.A O 1.045 1.435 LIG 1 O ALA 265.A O 0.550 2.430 LIG 1 N GLU 169.A OE2 0.439 2.666 LIG 1 H GLU 169.A CD 0.116 2.584 LIG 1 O ASN 253.A 1HD2 0.094 2.386 LIG 1 H ALA 265.A C 0.090 2.610 LIG 1 C ALA 265.A O 0.059 3.121 LIG 1 N ASN 253.A OD1 -0.037 3.142 LIG 1 C ALA 265.A O -0.039 3.219 LIG 1 N GLU 169.A HG3 -0.072 2.697 LIG 1 C PHE 168.A HB2 -0.081 2.781 LIG 1 N GLU 169.A CG -0.113 3.438 LIG 1 N GLU 169.A CD -0.125 3.450 LIG 1 N GLU 169.A CD -0.128 3.453 LIG 1 C MET 270.A HG2 -0.140 2.840 LIG 1 N PHE 168.A CD2 -0.163 3.488 .......... .... ... .. . -------------------------------------------------------------------------------- Now I want to further classify these contact interactions into more other types: Aromatic and Ionic (anion < - > cation). Is there any way in Chimera to achieve this? Or if I want to do it with some scripting, which atoms I would say are involved in ionic and aromatic interactions considering the distance value as well? I would be very much grateful if someone suggest me a way to do this. Thanks, Best regards, -- Shahid.