I'm trying to find CHARMM topology (and parameter?) file that defines AMP. The one I have, called top_all27_prot_lipid_na.inp, includes ADP and ATP but not AMP. I tried defining AMP in an analogous fashion to those two residue types, but the details are tricky to get exactly right. The file I've attempted to edit to include AMP is attached for those interested.
Anyone have any insight and/or a file I could use? Thanks!