Re: Dioxygen atom type with CHARMM36

From: Kenno Vanommeslaeghe (
Date: Tue Nov 11 2014 - 11:07:25 CST

I don't have a clear-cut answer to this question, but can offer some food
for thought:
Bottom line is, as always, that it all depends on what kind of accuracy
you need. I certainly wouldn't use it for any kind of quantitative (e.g.
free energy) calculation without stringent validation, but if you just
want qualitative sampling information on a system in which the oxygen does
not play a central role, a very approximate model that is either based on
"OM" in toppar_all36_prot_heme.str or OG2D1 in CGenFF may be good enough.

On 11/11/2014 11:11 AM, Francesco Pietra wrote:
> Hello:
> My question is about the heroic use of dioxygen data from
> toppar_all22_prot_heme.str (by zeroing the charges) and
> par_all27_prot_lipid.rtf for CHARMM36. I refer to free dioxygen in TIP3
> water solution.
> With CHARMM36 the "OM" type of previous FF version should be changed. Is
> the change to "OG2D1" the best compromise?
> Thanks for advice
> francesco pietra

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