Hi Daniel,
I can't understand why ... if possible, I'd like look at your two sets of
files. Please use, say, 10 snapshots in each case, to demonstrate the
differences.
All the best,
Ray
==========================================
Ray Luo, Ph.D.
Associate Professor
Dept Molecular Biology & Biochemistry
University of California, Irvine, CA 92697
USPS: PO Box 3900 Email: rluo.uci.edu
Phones: (949) 824-9528, 9562
Web: http://rayl0.bio.uci.edu/
==========================================
-----Original Message-----
From: owner-amber.scripps.edu [mailto:owner-amber.scripps.edu] On Behalf Of
Daniel Emery
Sent: Monday, December 08, 2008 8:28 AM
To: amber.scripps.edu
Subject: AMBER: Problem with MMPBSA
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 - 01:11:51 PST