[gmx-users] Going from OPLS-AA dihedrals to CHARMM22 dihedrals.

[Dawid das]

Dear Justin,

In this case may I use Ryckaert-Bellemans dihedral (func. type 3) for one
part of the new residue and proper dihedral (multiple) (func. type 9) for
the rest? Is this "mixing" allowed?


2014-07-16 1:34 GMT+01:00 Justin Lemkul <jalemkul at vt.edu>:

>
>
> On 7/15/14, 1:29 PM, Dawid das wrote:
>
>> Dear Gromacs experts,
>>
>> I have following issue. I need torsional parameters from this publication:
>> D. V. Dmitrienko et al., Biochemistry (Moscow), 2006, Vol. 71, No. 10,
>> 1133-1152
>> where OPLS-AA FF has been used but I need to adapt them for CHARMM22 FF.
>> Now the thing is that there are two different torsional energy expression
>> used in those FFs.
>> How can I go from one to another?
>> To be precise I want to adapt parameters from the above mentioned
>> publication to expression  for torsional potential from this publication:
>>
>> N. Reuter et al., J. Phys. Chem. B, 2002, Vol. 106,  6310-6321
>>
>> Any help will be appreciated.
>>
>>
> It's not wise to try to hack parameters developed for one force field into
> another.  Dihedrals are especially dangerous, because their validity is
> also dependent upon the nonbonded interactions of atoms 1 and 4 in the
> interaction; differences in charges and LJ parameters between OPLS-AA and
> CHARMM will make the dihedral non-transferable.
>
> -Justin
>
> --
> ==================================================
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> Justin A. Lemkul, Ph.D.
> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>
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> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
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