[gmx-users] Strange value for Protein-Substrate interaction

[Alan Wilter Sousa da Silva]

Hi List!

	I did 2 MD of a protein + substrate under different conditions.
Protein has charge 6 and substrate 1 (total +7e).  (1) I used cut-off (1.4
nm) and no ions; and (2) with ions (PME) to vanish the total charge of my
system.  I'm interest in the energy interaction between protein/substrate
and trying to evaluate the contribution of ions.  In the MD with ions
energy values seem OK.  However when ran MD with no ions I got the strange
result below:


Energy                      Average       RMSD     Fluct.      Drift
Tot-Drift  -kT ln<e^(E/kT)>
-------------------------------------------------------------------------------
Coul-LR:PR-Substrate           -inf          0          0 -4.01165e+34
-4.00371e+36         nan
Total                          -inf         --         --         --
--         nan         inf

Looking MD via VMD I don't see anything spurious, substrate and Protein
keep a low RMSD, none atom traveling around the box.

Could someone, please, give some tip here?  Thanks in advance.

Cheers,

-----------------------
Alan Wilter S. da Silva
-----------------------
 Laboratório de Física Biológica
  Instituto de Biofísica Carlos Chagas Filho
   Universidade do Brasil/UFRJ
    Rio de Janeiro, Brasil