I am a beginner using charmm.
I have a question about running script "gen-prot.inp". When reading sequence from PDB file, why do we use 4pti-a.pdb not 4pti.pdb ? Is it because of the number of peptide chain ?
Then, can we identify the number of peptide chain from the number of chain ID ?

Finally, how do you make 4pti-a.pdb from 4pti.pdb ?
Is there any script that change from 4pti.pdb to 4pti-a.pdb or do I need to change them by hand?

Thank you.