Re: psfgen - pdbalias when using readpsf

From: Peter Freddolino (
Date: Thu Dec 15 2016 - 14:40:40 CST

> On Dec 15, 2016, at 3:28 PM, Brian Radak <> wrote:
> I'm not sure that "pdbalias residue" is doing what is expected - can someone enlighten me?
> I am reading a pre-made psf/pdb/coor/vel set from files, but want to change some of the topologies that are used. Specifically I want every instance of the standard C36 residues HSD, HSE, and HSP to become HIS (a new topology that I made and loaded an RTF for). This is essentially the same thing as opening the PSF and PDB and running sed to replace HSD/HSD/HSP with HIS. I thought the following would do what I want:
> pdbalias residue HSD HIS
> pdbalias residue HSE HIS
> pdbalias residue HSP HIS
> readpsf <blah>
> writepsf <some new psf>
> writepdb <some new pdb>
> but this does not seem work as I wanted it to (the output pdb still contains HSD residues in my test). Does pdbalias only work when using the segment command? If so, is that a bug or a feature?

Yes it does only work when using segment commands, and this is a feature. pdbalias only applies to entries being read from topology files. The set of commands that you have never use topology files, they just read and then re-write existing information from a psf. Using sed or totally rebuilding the psf with that aliasing in place would probably be a cleaner way to accomplish what you’re trying to do here.

Quoting the psfgen manual (
pdbalias residue

Provide translations from residues found in PDB files to proper residue names read in from
topology definition files. Proper names from topology files will be used in generated PSF and PDB

> Brian
> --
> Brian Radak
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