Re: [AMBER] Converting CGenFF CHARMM parameters in tleap

From: He, Amy via AMBER <amber.ambermd.org>
Date: Tue, 20 Feb 2024 20:43:26 +0000

Hi Collin,

I was under the impression that
“loadamberparams” only read Amber frcmod/parm.dat files.

In addition to .frcmod, typical reusable file formats for nonstandard residues are:
OFF Library files (.lib) or Prep input files (.prepi).

If you wish to write these reusable Amber parameter files from the CHARMM files, the ParmEd program might be helpful. You can find more information on ParmEd in the recent Amber Manual or from the documentation site:
https://parmed.github.io/ParmEd/html/index.html

The parameter/topology (.prmtop) files may not be reusable in tleap, but it could be one input for ParmEd. 


--
Amy He
Hadad Lab . OSU
He.1768.osu.edu
From: Collin Nisler via AMBER <amber.ambermd.org>
Date: Tuesday, February 20, 2024 at 1:48 PM
To: Collin Nisler via AMBER <amber.ambermd.org>
Subject: [AMBER] Converting CGenFF CHARMM parameters in tleap
Hello, I am attempting to build an RNA system in tleap that contains a nonstandard residue, in addition to a standard RNA duplex. I have CHARMM parameters and a psf file for the nonstandard residue, and have created a separate .prmtop and mol2 file for this residue. I am having difficulties creating a solvated system with .crd and .prmtop files for the entire system using tleap. I load the .prmtop into tleap using the "loadamberparams" command, and get the following messages:
Warning: %FLAG: mass not read - omitting
Warning: %FORMAT(20a4): mass not read - omitting
Warning: Incomplete Angle line:
%FLAG HBOND_BCOEF
Warning: Incomplete Improper Torsion line:
%FLAG HBCUT
When I then attempt to solvate the system, I get the following message for each atom in the nonstandard residue:
(using default radius 1.500000 for P1)
Then finally, when I attempt to output the files from tleap, I get the following error for each atom:
Error: For atom (.R<EQ1 1>.A<P1 1>) could not find vdW (or other) parameters for type (P1)
I am new to Amber, but I have tried to familiarize myself with the file formats and as far as I can tell, all the parameters are present in the .prmtop file generated for the nonstandard residue that I load into tleap. Is tleap just not meant to read .prmtop files, and if so how else could I go about converting CHARMM parameters generated from CGenFF to Amber format? Thanks very much for any help.
Collin
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Received on Tue Feb 20 2024 - 13:00:02 PST
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