Re: [AMBER] Implicit solvent simulation with Andersen thermostat

From: Hai Nguyen <>
Date: Thu, 26 Mar 2015 01:56:16 -0400


Like Jason's case, I have been using Langevin (ntt=3) for implicit solvent
(GB) and have no problem with its speed.

You can see our benchmark (up to 100 residues), equil protocol, speend
(ns/day) ... in the supp of our paper:
Folding Simulations for Proteins with Diverse Topologies Are Accessible in
Days with a Physics-Based Force Field and Implicit Solvent
you can vary the gamma_ln value to reduce/increase the 'viscosity' in your
simulation. Smaller number will significantly increase your sampling speed
while keeping the same thermodynamic property.

On Wed, Mar 25, 2015 at 7:41 PM, Glenn Carrington [bs10g3c] <> wrote:

> Dear Amber users,
> I'm planning to run a large implicit solvent simulation of myosin using
> AMBER 12. I had a few questions that I was hoping someone could help me
> with.
> 1 - The molecule is quite big and I plan to use GPU's. The tutorials i
> looked at use a Langevin thermostat, but the GPU page states that this is
> very inefficient and I should use the Berendsen or Anderson thermostats. As
> the AMBER manual rules out the Berendsen due to issues with implicit
> solvent model, I guess I'm stuck with the Anderson (ntt=2). Could anyone
> with experience let me know the best setting for vrand (other than the
> default of 1000?) From what I've read this is the only variable associated
> with the Anderson thermostat?

(check my reply above)

btw, don't expect to see dramatically speedup in the speed for implicit
solvent MD with large system (in term of ns/day you get) vs explicit water
MD. The benefit of speeding up is in sampling efficiency (check posted

> 2 - What settings do people use to equilibrate an implicit solvent
> simulation? Is the only consideration increasing the temperature from 0K to
> the target temp?
We posted our equil protocol in the paper above. Generally, the equil
protocol depends on your system. For example if you need to use another
program (like tleap) to build extra sidechain, residue, you might want to
restraint other part of you system and relax the built part first in your

In our experience, increasing T from 100K to targeted T is better choice
than 0K.

> 3 - Parts of the structure I'm using has been homology modelled. Are there
> any established protocols that anyone is aware of that I could use to test
> the stability of my structure?

(no comment)

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Received on Wed Mar 25 2015 - 23:00:02 PDT
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