[gmx-users] Best Lipid parameters...

[Erik Lindahl]

jozef hritz wrote:

>	Dear Senthil,
>I found Your question in gromacs mailing list. 
>Have you got answers? I can't find any in the mailing list and I am sure
>answer is interesting for many users.
>
>	Thanks
>
>								Jozef
>
>
>>I am working on a lipid/protein/water/ions system and am looking for the 
>>best forcefield available to describe this system.
>>I see that there is an improved lipid forcefield ffG43a2x in 
>>the  contributed topology section.
>>Is this the best lipid parameter file available? I understand that just
>>two new atomtypes have been added to the general gromos forcefield?
>>How different is this forcefield from Tielemens Lipid.itp available from 
>>his website? Any ideas or suggestions?
>>
>>Thanks.
>>
>>Senthil
>>
HI Jozef & Senthil,

I think I've covered this before, but it won't hurt to do it again: 
Gromos96 in general is a quite nice united atom force field, but the 
carbon parameters used to be optimized for shorter chains, so they gave 
way too low area/lipid for lipids.

The ffG43a2x is an extension where one of my diploma students 
reparametrized carbons to suit the CH3 and CH2 for long chains. These 
parameters reproduce the area/lipid of at least DPPC within 1% of the 
experimental value (it is slightly dependent on the size of your system 
too). We've used it for tons of simulations with very good results.

There are a newer set of Gromos96 carbon parameters which should improve 
the situation significantly, but I've not been able to test it myself 
and it's not included in the distribution yet.

Cheers,

Erik