[AMBER] Issue with MMGBSA Calculation for Protein–siRNA Complex

From: YASHIKA . via AMBER <amber.ambermd.org>
Date: Fri, 19 Dec 2025 14:00:26 +0530

Dear Team,

I am performing MMGBSA calculations on a protein–siRNA complex and
encountering an error. Below are the details:

*System and files:*

   -

   *Complex topology (complex_wt_nosolvent.parm7):* 8691 atoms, 502
   residues, 3 molecules
   -

   *Protein topology (protein_wt.parm7):* 7352 atoms, 460 residues, 1
   molecule
   -

   *siRNA topology (sirna_wt.parm7):* 1339 atoms, 42 residues, 2 molecules
   -

   *Trajectory (traj.mdcrd):* 8691 atoms, 502 residues, 3 molecules;
   stripped of water and ions

*MMGBSA input:*

&general
   startframe=1
   endframe=5000
   interval=5
   verbose=2
   keep_files=0
/

&gb
   igb=5
   saltcon=0.150
   radiopt=0
/
*Observed error:*
Loading and checking parameter files for compatibility...
cpptraj found! Using /home/leena/miniconda3/envs/amber_fix/bin/cpptraj
mmpbsa_py_energy found! Using
/home/leena/miniconda3/envs/amber_fix/bin/mmpbsa_py_energy
Preparing trajectories for simulation...
1000 frames were processed by cpptraj for use in calculation.

Running calculations on normal system...

Beginning GB calculations with
/home/leena/miniconda3/envs/amber_fix/bin/mmpbsa_py_energy
  calculating complex contribution...
  File "/home/leena/miniconda3/envs/amber_fix/bin/MMPBSA.py", line 100, in
<module>
    app.run_mmpbsa()
  File
"/home/leena/miniconda3/envs/amber_fix/lib/python3.10/site-packages/MMPBSA_mods/main.py",
line 224, in run_mmpbsa
    self.calc_list.run(rank, self.stdout)
  File
"/home/leena/miniconda3/envs/amber_fix/lib/python3.10/site-packages/MMPBSA_mods/calculation.py",
line 82, in run
    calc.run(rank, stdout=stdout, stderr=stderr)
  File
"/home/leena/miniconda3/envs/amber_fix/lib/python3.10/site-packages/MMPBSA_mods/calculation.py",
line 156, in run
    raise CalcError('%s failed with prmtop %s!' % (self.program,
CalcError: /home/leena/miniconda3/envs/amber_fix/bin/mmpbsa_py_energy
failed with prmtop
/home/leena/Downloads/scmv1/simulation/184_22_out/complex_wt_nosolvent.parm7!

Fatal Error!
All files have been retained for your error investigation:
You should begin by examining the output files of the first failed
calculation.
Consult the "Temporary Files" subsection of the MMPBSA.py chapter in the
manual for file naming conventions.
Could anyone please advise on what might be causing this failure, or
suggest steps to resolve it?
Thank You
With regards
Yashika
NSUT, Delhi
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Received on Fri Dec 19 2025 - 01:00:02 PST
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