On 2011-03-31 17.19, Alan Wilter Sousa da Silva wrote:
I know it's supported.

I was just investigating the possibility since I build acpype to create
topologies for gromacs, but also it converts from amber to gromacs (like
amb2gmx.pl <http://amb2gmx.pl>), and so I was wondering about RB with 6
coefficients since multiple proper dihedrals is only supported for gmx
4.5 and above.
Unfortunately RB only goes to 5 and it would be a pain to support more since the tpr format would have to be updated. The current solution with the type 9 dihedrals is a royal pain in the neck too. I've actually written a script that converts the present rtp files to contain *all* bonded interactions explicitly (with parameters), and it replaces the 9 type dihedrals with multiple 1 type dihedrals (lots of them with all zeros, LOL).

But I don't want to fuss about it. If to forget about GMX 4.0.x and
below is the way, so it will be.

Thanks,

Alan

On 31 March 2011 16:08, David van der Spoel <sp...@xray.bmc.uu.se
<mailto:sp...@xray.bmc.uu.se>> wrote:

    On 2011-03-31 15.27, Alan Wilter Sousa da Silva wrote:

        Hi there,

        Since ILDN dihedrals has some parameters with up to periodicity
        6, I was
        wondering if it's possible to convert it in RB with 6
        coefficients. If
        so, what would be the formula? For example, for converting the usual
        Amber99SB to RB I have:

    ILDN is already supported in the latest gromacs releases, by simply
    using multiple proper dihedrals. Why would you want to change it?



        if phase in [0, 180]:

        if kPhi > 0: V[period] = 2 * kPhi * cal

        if period == 1:

                                 C[0] += 0.5 * V[period]

        if phase == 0:

                                     C[1] -= 0.5 * V[period]

        else:

                                     C[1] += 0.5 * V[period]

        elif period == 2:

        if phase == 180:

                                     C[0] += V[period]

                                     C[2] -= V[period]

        else:

                                     C[2] += V[period]

        elif period == 3:

                                 C[0] += 0.5 * V[period]

        if phase == 0:

                                     C[1] += 1.5 * V[period]

                                     C[3] -= 2 * V[period]

        else:

                                     C[1] -= 1.5 * V[period]

                                     C[3] += 2 * V[period]

        elif period == 4:

        if phase == 180:

                                     C[2] += 4 * V[period]

                                     C[4] -= 4 * V[period]

        else:

                                     C[0] += V[period]

                                     C[2] -= 4 * V[period]

                                     C[4] += 4 * V[period]


        So, as you can see, I can handle up to 4 periods (C[5] is always
        0, but
        not with ILDN and I need to add C[6] rules as well).

        Any ideas? Many thanks in advance,

        Alan
        --
        Alan Wilter SOUSA da SILVA, DSc
        Bioinformatician, UniProt - PANDA, EMBL-EBI
        CB10 1SD, Hinxton, Cambridge, UK
        +44 1223 49 4588



    --
    David van der Spoel, Ph.D., Professor of Biology
    Dept. of Cell & Molec. Biol., Uppsala University.
    Box 596, 75124 Uppsala, Sweden. Phone:  +46184714205.
    sp...@xray.bmc.uu.se <mailto:sp...@xray.bmc.uu.se>
    http://folding.bmc.uu.se
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--
Alan Wilter SOUSA da SILVA, DSc
Bioinformatician, UniProt - PANDA, EMBL-EBI
CB10 1SD, Hinxton, Cambridge, UK
+44 1223 49 4588



--
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:  +46184714205.
sp...@xray.bmc.uu.se    http://folding.bmc.uu.se
--
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