First off, make sure you're using a recent, fully patched version of
AmberTools 1.5. Use tleap or xleap to generate the files (not sleap).
There have been similar issues in the past that were fixed.
We also recommend using the most up-to-date version of GLYCAM (see
glycam.org/params).
Ideally, the order doesn't matter, and we try to fix conflicts as soon
as we know about them, but occasionally they happen. In that case, it
is generally better to load ff99SB first and then Glycam. If you are
using the most recent tools and parameters, please give us more
details about the system you are building as well as the versions of
AT and glycam.
On Thu, Dec 8, 2011 at 12:07 PM, Sai Kumar Ramadugu <sramadugu.gmail.com> wrote:
> Dear Amber Users,
> I have a complex of protein with a disaccharide. When I load the ff99Sb
> first and GLYCAM second versus GLYCAM first and ff99SB second, the energy
> terms for a zero step minimization in gas phase are different for angle,
> dihedral, 1-4LJ, 1-4Coulomb, and the total potential energy.
> Below are the output values from the respective minimizations:
> 1. ff99SB first, GLYCAM second
>
> NSTEP ENERGY RMS GMAX NAME
> NUMBER
> 1 -1.3061E+03 1.3969E+02 3.4776E+03 SG 1025
>
> BOND = 85.4389 ANGLE = 175.7590 DIHED =
> 231.3310
> VDWAALS = 855.0251 EEL = -7406.8357 HBOND =
> 0.0000
> 1-4 VDW = 428.9510 1-4 EEL = 4324.2069 RESTRAINT =
> 0.0000
>
> 2. GLYCAM first and ff99SB second
>
> NSTEP ENERGY RMS GMAX NAME
> NUMBER
> 1 -2.3382E+02 1.3969E+02 3.4776E+03 SG 1025
>
> BOND = 85.4389 ANGLE = 170.9682 DIHED =
> 881.3310
> VDWAALS = 855.0251 EEL = -7406.8357 HBOND =
> 0.0000
> 1-4 VDW = 430.1394 1-4 EEL = 4750.1157 RESTRAINT =
> 0.0000
>
>
> The differences appear due to the different values of equilibrium angle
> value and force constant value for one atom,
> the dihedral angle force constants and phase are different, the scee and
> scnb values are different after the mixed scaling is included. Therefore
> the respective energy terms are different in the output files.
>
> Is it due to the fact that some of the atomtypes are same in both ff99SB
> and GLYCAM and the parameters get overwritten based on the order of
> inclusion of leaprc files in xleap?
> When I was going through the manual (AmberTools) for carbohydrates, the
> order in the manual is load GLYCAM first and ff99SB second.
> Does this mean that whenever you have a protein and sugar complexed, the
> order of leaprc files is always 1st GLYCAM and 2nd ff99SB?
>
> Any suggestions will be helpful.
>
>
> Regards
> Sai
> _______________________________________________
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> AMBER.ambermd.org
> http://lists.ambermd.org/mailman/listinfo/amber
--
:-) Lachele
Lachele Foley
CCRC/UGA
Athens, GA USA
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Received on Thu Dec 08 2011 - 09:30:03 PST
