AMBER: Problem with MMPBSA

From: Daniel Emery <Daniel.Emery.unige.ch>
Date: Mon, 08 Dec 2008 17:28:22 +0100

Dear all,

I have a problem to calculate the binding energy between the biotin and
the streptavidin.
When I calculate the interaction energy between the biotin and a monomer
of the streptavidin, there is no problem. See the results below :

# DELTA
# -----------------------
# MEAN STD
# =======================
ELE -90.42 8.91
VDW -65.36 3.31
INT 0.00 0.00
GAS -155.79 8.68
PBSUR -8.18 0.16
PBCAL 109.32 7.51
PBSOL 101.14 7.52
PBELE 18.90 4.90
PBTOT -54.65 4.61
GBSUR -8.18 0.16
GB 107.08 6.91
GBSOL 98.90 6.93
GBELE 16.66 4.24
GBTOT -56.89 3.97

But, when I calculate the same interaction between the biotin and the
streptavidin in the tetrameric form, I have trouble with the result of
the PBSA calculation.
The result for the GBSA calculation looks OK but the PBSA results are so
different and the standard deviation is almost the same as the mean
result. See below:

# DELTA
# -----------------------
# MEAN STD
# =======================
ELE -72.87 11.04
VDW -62.17 4.68
INT -0.00 0.00
GAS -135.05 12.99
PBSUR -10.35 0.21
PBCAL -22.07 119.30
PBSOL -32.42 119.31
PBELE -94.94 117.26
PBTOT -167.46 116.31
GBSUR -10.35 0.21
GB 114.05 10.86
GBSOL 103.70 10.73
GBELE 41.18 4.29
GBTOT -31.34 5.77

The problem come from the electrostatic part of the GB calculation.
I use, in these 2 cases, the same (exept the atom definition) input for
the calculation of the binding energy.

With these informations, have somebody a explanation or have somebody
the same problem?
Have you an idea to fix it?

Thanks a lot for your help.

Regards,
Daniel

-- 
EMERY Daniel
Ph.D. Student (Lab. R1)
Department of Organic Chemistry
University of Geneva
30, quai Ernest-Ansermet
CH-1211 Geneva 4
+41 22 379 61 55
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Received on Wed Dec 10 2008 - 01:10:30 PST
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