[gmx-developers] Umbrella code extension / flat bottom potential

Berk Hess hess at kth.se
Thu Feb 13 08:50:53 CET 2014


I guess you mean flat-bottomed position restraints.
I am talking about the pull code (between COM iso atoms).

Berk

On 02/13/2014 04:05 AM, Mark Abraham wrote:
> It's been in master branch for about a year :-)
>
> Mark
>
>
> On Wed, Feb 12, 2014 at 8:20 PM, Berk Hess <hess at kth.se 
> <mailto:hess at kth.se>> wrote:
>
>     On 02/12/2014 04:55 PM, David van der Spoel wrote:
>
>         On 2014-02-12 15:24, Sabine Reisser wrote:
>
>             Hi,
>
>               "It seems like your potential would not need an extra
>             parameter (it
>             should
>             equal a flat bottomed potential with lower limit 0)."
>
>         A flat bottom potential is already in the code and we have
>         used it extensively. Jochen Hub has implemented it.
>
>     Not in the main distribution.
>
>     Cheers,
>
>     Berk
>
>
>             Yes, this is exactly what I mean.
>
>             Thanks & cheers
>             Sabine
>
>
>
>             On 02/12/2014 03:08 PM, Berk Hess wrote:
>
>                 Hi,
>
>                 This indeed looks like a flat-bottomed restraint
>                 potential. I had
>                 proposed that addition to the pull code for 5.0 in a
>                 request for
>                 feedback, which I also posted to the developers list.
>                 But since I didn't
>                 receive any response on this point I didn't implement
>                 it. Also because a
>                 general flat bottomed potential needs an extra
>                 (distance) parameter. It
>                 seems like your potential would not need an extra
>                 parameter (it should
>                 equal a flat bottomed potential with lower limit 0).
>                 Since it's too late
>                 for 5.0, I would propose to implement the flat
>                 bottomed potential for
>                 5.1.
>
>                 Cheers,
>
>                 Berk
>
>                 On 02/12/2014 02:31 PM, Shirts, Michael (mrs5pt) wrote:
>
>                     Hi, Sabine-
>
>                     So, this looks like the distance restraint
>                     potential (bond function
>                     10) in
>                     section 4.3.4 of the manual that matches this
>                     potential function.  Right
>                     now, this potential can only be applied.  However,
>                     there is a planned
>                     fix
>                     for 5.0 that will include the ability to add all
>                     bonded interactions in
>                     between arbitrary atoms in the system, even if
>                     they are not in the same
>                     molecule.
>
>                     I BELIEVE there is an extension to the pull code
>                     that would allow
>                     general
>                     bonded potentials to be used between COMs of index
>                     groups as well but
>                     I'm
>                     not as certain about that.
>
>                     I think that these planned changes will capture
>                     the functionality
>                     that you
>                     are describing.  Is that correct?
>
>                     Best,
>
>                     ~~~~~~~~~~~~
>                     Michael Shirts
>                     Assistant Professor
>                     Department of Chemical Engineering
>                     University of Virginia
>                     michael.shirts at virginia.edu
>                     <mailto:michael.shirts at virginia.edu>
>                     (434)-243-1821
>
>
>
>                     On 2/12/14, 8:20 AM, "Sabine Reisser"
>                     <sabine.reisser at kit.edu
>                     <mailto:sabine.reisser at kit.edu>> wrote:
>
>                         Hello,
>
>                         I have implemented an extension to the
>                         existing umbrella code in
>                         Gromacs
>                         version 4.6.3. It is a semiharmonic potential
>                         which sets a maximum
>                         distance between two index groups. When this
>                         distance is trespassed, a
>                         force kicks in and bounces the pull group
>                         back, when the distance is
>                         below the threshold, motions are completely
>                         unrestrained. I use this
>                         code to simulate pores of antimicrobial
>                         peptides, to keep the peptides
>                         in close vicinity without actually interfering
>                         with the pore formation
>                         process.
>                         The code can also be used to make sure several
>                         peptides bind to the
>                         same
>                         side of a membrane or in ligand-binding
>                         simulations.
>                         The relevant part of the extended code is no
>                         longer than 10 lines,
>                         but I
>                         naturally had to change other files in order
>                         to read the modified input
>
>                     >from the mdp files, too. Affected binaries are
>                     mdrun and grompp.
>
>                         Instead of providing this singular modified
>                         Gromacs 4.6.3 as a tarball
>                         for downloading, I would like to get this
>                         extension into the official
>                         release so that it is maintained also in
>                         future releases.
>
>                         What is the procedure to achieve this or who
>                         is the best person to
>                         address?
>
>                         With best regards
>
>                         Sabine Reißer
>
>
>                         ---------------------------------
>                         Dipl. phys. Sabine Reißer
>                         Theoretical Chemical Biology
>                         Institute for Physical Chemistry
>                         Karlsruhe Institute for Technology (KIT)
>                         Germany
>
>
>
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