Re: [AMBER] Atom type of Calcium

From: Sunita Patel <>
Date: Wed, 20 Feb 2019 17:35:06 +0530

Dear David,

I have to run my simulations in amber12 using amber ff99SB force field for
comparison purpose. I tried using source leaprc.tip3p."
but it didn't recognize the Ca2+ ions.
I need your guidance please to add Ca2+.


On Tue, Feb 12, 2019 at 7:56 PM David Case <> wrote:

> On Tue, Feb 12, 2019, Sunita Patel wrote:
> >Can you please provide some links. I was thinking it would be straight
> >forward like protein atom types.
> It *is* straightforward, although I agree that the manual section on
> ions is more complex than it needs to be. Once you select a water model
> (via "source leaprc.water.xxxx"), monoatomic ions for that model are
> automatically loaded as well. The exact parameters used are printed to
> the screen when you load a water file.
> You can use the "desc" command in tleap to see which ions are present.
> Following the PDB standard, the residue and atom name for calcium2+ are
> both "CA". So make sure your input PDB file labels calcium as CA, and you
> should be fine.
> [Aside: the ff99SB force field is way out of date. If you are not using
> AmberTools18, you should upgrade to that version, and use ff14SB for
> proteins.]
> [Aside to developers: the "Ions" section of the Reference Manual is
> written only for some hypothetical super-expert who wants to know
> details of ion parameters we no longer use. Can someone add an opening
> paragraph describing what users are actually supposed to do in practice,
> i.e. that the water leaprc files include ions, and that the recommended
> parameters are indentified there?]
> ...good luck....dac
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Received on Wed Feb 20 2019 - 04:30:02 PST
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