[gmx-users] OPLS/AA + TIP5P, anybody?

[gigo]

Dear Chris,
Authors answered me very quickly. They did not have such a problem, but 
I still don't know the details of their input. They used gromacs-3.3, so 
I decided to give the old one a try. I did some tests with 3.3.4. 
Although the same problem occurred during steep minimization, some 
interesting things popped out. When I tried to grompp the system with 
plain tip5p for cg minimization, it failed:
"ERROR: can not do Conjugate Gradients with constraints (8484)", even 
though I did not set any constraints. The error is the same for tip4p 
unless you use flexible model, which tip5p does not have - the water had 
to be constrained then. I guess that treatment of virtual sites in 
gromacs-3.3 has something to do with this. I noticed, that constraints 
make simulations with tip5p more stable. It should not happen, that the 
LP virtual atoms are pulled further then the defined 0.7 from the 
oxygen, right? I will keep you updated.
Best Regards,
Grzegorz


On 2013-09-29 04:50, Christopher Neale wrote:
> Dear Gigo:
> 
> that's a good comprehensive testing and report. Please let us know
> what you find out from those authors.
> Their paper was short on methods (unless I missed it... I didn't check
> for any SI), so perhaps they did something
> non-standard and didn't report it.
> 
> I think at this point it is a good idea for you to file a redmine
> issue. It's not a gromacs error per se, but
> if this is true then pdb2gmx or grompp should give a warning or error
> for the combination of oplsaa and tip5p.
> 
> Chris.
> 
> gigo gigo at ibb.waw.pl
> Sun Sep 29 00:59:42 CEST 2013
> Previous message: [gmx-users] OPLS/AA + TIP5P, anybody?
> Next message: [gmx-users] Restarting simulation -s. files?
> Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
> Dear Chris,
> I am really grateful for your help. This is what I did, with additional
> LJ terms on LP1 and LP2 of tip5p:
> - 5000 steps of steepest descent with positions restraints on protein
> and flexible water (flexibility like in tip4p),
> - 5000 steps of steep, no restraints, flexible water,
> - 5000 steps of cg, flexible water,
> - 100000 steps of MD with posres and constrained bond lengths, very 
> weak
> temp coupling (v-rescale), starting without generating of initial
> velocities, so its heating very slowly to 300K, no pressure coupling
> - 100000 steps of MD with posres, no constraints, v-rescale, nvt
> - 100000 steps of MD, no posres, nvt,
> - 100000 steps of MD, v-rescale, Berendsen pressure coupling,
> - 100000 steps of MD, v-rescale, Parrinello-Rahman pressure coupling.
> 
> Output of this chain, after removing LJ from LP, became input for 4
> simulations just like the last one from the above chain, with or 
> without
> posres and constraints turned on.
> Results:
> 1) Posres off, constraints off :
> "step 0"
> "WARNING: Listed nonbonded interaction between particles 1157 and 1163"
> <== Why does it say "particles" and not "atoms"? Nevermind, its lysine
> on the surface of the protein, one of atoms is dimensionless hydrogen.
> (...)
> "step 63: Water molecule starting at atom 7923 can not be settled."
> (...)
> "Segmentation fault"
> 
> 2) Posres off, constraints on :
> Warning like above + LINCS warnings, all for charged aminoacids on
> surface of the protein
> Segfault at step 63
> 
> 3) Posres on, constraints off, had to add refcoord_scaling = COM :
> "WARNING: Listed nonbonded interaction between particles 3075 and 3079"
> <== arginine on the surface, dimensionless hydrogen
> 
> 4) Posres on, constraints on, refcoord_scaling = COM :
> Same warnings, several other positively charged dimensionless hydrogens
> listed, waters could not be settled, segfault.
> 
> I tried to run few other peptides and proteins with tip5p, 100% of
> crashes.
> 
>> Also, tip5p has been used successfully with the charmm foce field:
>> http://pubs.acs.org/doi/abs/10.1021/ct700053u
> 
> Yes, there are no dimensionless charged hydrogens there except of these
> on ... tip3p, tip4p and tip5p water.
> 
>> (...)
>> http://pubs.acs.org/doi/abs/10.1021/ct300180w
>> (...)
>> Are you using halogens with oplsaa-x?
> 
> No, I use OPLSAA distributed with Gromacs.
> 
> 
>> Standard oplsaa (non-x) and tip5p seem to be a fine combination:
>> http://www.sciencedirect.com/science/article/pii/S0006349507713863
>> 
>> you might want to contact the authors of that paper to see if they
>> ever had such problems.
> 
> Thank you, I will ask them. I am starting to be sure, though, that it 
> is
> not possible to run any simulations with tip5p and proteins (containing
> arginine for example) without some tricks, strengthening/constraining
> bonds at least. It happened during the minimization, that the distance
> between HHxy and NHx in arginine grew up to 1.48A, while HHxy was
> landing on LP of the water. Repeatability is 100%.
> Regards,
> Grzegorz