Problems reading CHARMM topology and parameter files with PyChemShell

Dear all,

I am following the p450 tutorial to set up a QM/MM optimization of a metalloprotein in Py-ChemShell, however, I am having problems for copper to be recognized. I am following the structure below in my script:

First, convert user-defined CHARMM files for camphor to DL_FIELD format

udff = DL_FIELD.charmm2udff(rtf=‘…/1_solvation/mytop.rtf’,
prm=‘…/1_solvation/mytop.prm’, version=‘CHARMM36_prot’)

Now use DL_FIELD to define the forcefield using built-in CHARMM36_prot

NB: cutoff distance defined in a.u.

my_ff = DL_FIELD(ff=[‘CHARMM36_prot’, udff],
override_builtin=False, original_tip3p=False)

In mytop.rtf and mytop.prm I have included all my system’s atom types, including the copper ion.

Here is what I get in the output:

Residues (i.e. DL_FIELD molecule types) not found:
CU2P

Any idea how to solve this?

Thank you!