[gmx-users] Lipid simulation temperature

[Justin A. Lemkul]

Jian Dai wrote:
> Hi, dear all:
> What is the highest possible simulation temperature for lipid bilayer 
> systems. The main transition temperatures for DPPC and POPC are about 
> 315K and 270K, respectively. However, we have cholesterols in our systems.
> I've gone through some literatures and found that people used 425K in a 
> MC/MD hybrid simulation and 350K in a MD simulation. We are actually 
> doing simulated annealing manually, i.e., raise the temperature to a 
> high value first (350K) and then cool it down gradually in a series of 
> relatively short simulations to 310K and the goal is to make the system 
> nicely equilibrate.
> Any suggestions? Thank you.

My guess would be trial and error.  I have seen, for example, at least one REMD 
study of a peptide in a membrane using restraints to maintain suitable 
properties of the membrane (around 500 K, I believe).  I don't know of any 
systematic study that has ever determined how high one can conduct a simulation 
and still have the lipid parameters be valid.  Certainly of concern would be the 
properties of the water, since at very high temperature the water model will 
likely break down, and of course the physical properties of the lipids.  Most 
force fields are designed to operate around physiological temperature, and may 
be sensitive to extreme conditions.

-Justin

> Jian
> 

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Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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