[gmx-users] REMD - replicas sampling in temperatures beyond the assigned range

[NISHA Prakash]

Dear all,

I have conducted a 10ns REMD simulation for a protein ligand complex with
the temperature range - 270 to 350 K, however the temperature distribution
plot of the replicas show that the sampling has occurred at higher
temperatures as well that is beyond 350K -
Below is an excerpt from the temperature xvg file


@    title "Gromacs Energies"
@    xaxis  label "Time (ps)"
@    yaxis  label "(K)"
@TYPE xy
@ view 0.15, 0.15, 0.75, 0.85
@ legend on
@ legend box on
@ legend loctype view
@ legend 0.78, 0.8
@ legend length 2
@ s0 legend "Temperature"
    0.000000    0.000000
   10.000000  350.997864
   20.000000  353.618927
   30.000000  350.068481
   40.000000  353.921753
   50.000000  359.485565
   60.000000  353.463654
   70.000000  352.015778
   80.000000  350.657898
   90.000000  351.927155
  100.000000  354.539429
  110.000000  354.287720
  120.000000  349.436096
  130.000000  352.960541
  140.000000  351.631317
  150.000000  354.217407
  160.000000  350.185852
  170.000000  350.294434
  180.000000  350.980194
  190.000000  350.914429
                   ....
                   ....
 470.000000  349.224060
  480.000000  350.819458
  490.000000  348.541748
  500.000000  350.393127
  510.000000  398.775208
  520.000000  444.802856
  530.000000  470.899323
  540.000000  466.652740
  550.000000  465.600677
  560.000000  469.225555
  570.000000  470.548370
  580.000000  470.011566
  590.000000  470.643951
  600.000000  472.433197
  610.000000  470.451172
  620.000000  469.991699
  630.000000  469.073090
  640.000000  467.259521
  650.000000  464.561798
  660.000000  468.416901
  670.000000  468.754913
  680.000000  469.259613
  690.000000  467.641144
  700.000000  468.542328


Temperature coupling was done using Nose hoover algorithm.

Does this imply the sampling is wrong or insufficent?
Any help / suggestion is appreciated.

Thanking you in anticipation.

Nisha