I am studying an IDP with a lot of helical secondary structure, and trying to find a trajectory that I can use as an ensemble that fits my SAXS data. My starting models are the output from the Robetta prediction server.
I am converting the IDP to a coarse-grained model so I can let the simulation run for ~$10\mu s$. In the process of converting it, I use martinize2. The python script takes the .pdb file, an output file name, and a pointer to the dssp binary (which I have looked everywhere for and haven't been able to find an 'official' source...).
martinize2 -f ../data/pdb/Robetta2.pdb -x cg.gro -o topol.top -dssp /usr/local/bin/dssp
If I run martinize2.py without specifying the -dssp parameter, the script runs fine and outputs my coarse grained model. If I specify the binary (I have probably tried 3 different versions of dssp), or specify -ss using the output from a dssp webserver, I will get different errors.
Am I okay to exclude the dssp parameter? Will my coarse grain model have the appropriate constraints for helical secondary structure from the PDB file? What is dssp even for in this context?
EXAMPLES OF ERRORS:
WARNING - unknown-input - Could not identify the modifications for residues ['ALA190'], involving atoms ['3059-3HB']
File "/home/nick/.local/lib/python3.8/site-packages/vermouth/dssp/dssp.py", line 214, in run_dssp
raise DSSPError(message.format(err=process.stderr, file=tmpfile_name))
vermouth.dssp.dssp.DSSPError: DSSP encountered an error. The message was DSSP could not be created due to an error:
empty protein, or no valid complete residues
...
File "/home/nick/.local/lib/python3.8/site-packages/vermouth/dssp/dssp.py", line 214, in run_dssp
raise DSSPError(message.format(err=process.stderr, file=tmpfile_name))
vermouth.dssp.dssp.DSSPError: DSSP encountered an error. The message was Error parsing PDB at line 1
Error trying to load file "/home/nick/GROMACS/projects/CG-4/dssp_in_i6lpkoe1.pdb"
Expected record CRYST1 but found ATOM
...
File "/home/nick/.local/lib/python3.8/site-packages/vermouth/dssp/dssp.py", line 557, in run_system
raise ValueError(
ValueError: The length of the sequence (13) does not match the number of residues in the selection (227).