Re: [AMBER] MCPB with OPC water?

From: Gustavo Seabra <>
Date: Tue, 8 Sep 2020 09:09:55 -0400

Hi all,

Would anyone have experience in this area?

I appreciate any input here.

Gustavo Seabra.
On Thu, Sep 3, 2020 at 10:24 AM Gustavo Seabra <>
> Hi,
> Is there a specific reason why OPC water is *not* supported by MCPB? Would
> it be OK to change the tleap file to use OPC?
> Explanation:
> I'm preparing a system with and noticed that the default force
> field now is ff19SB, which is the recommended force field for AMBER now.
> (Amber20 Manual, page 319), while the water models available seem to be
> only TIP3P, SPCE and TIP4PEW, with the default being TIP3P (Amber20 manual,
> page 320).
> However, the combination of ff19SB and TIP3P is *not* recommended, and the
> recommendation now is to use the OPC model with ff19SB:
> *"Our results [19]showed that ff19SB pairs best with the more accurate
> water model OPC [20] , and that the older TIP3P model has serious
> limitations when used with the QM-based ff19SB. As a result, we strongly
> recommend using ff19SB with OPC, and we recommend against use with TIP3P."*
> (Amber20 Manual, page 36)
> So, I would like to know if there is any reason *not* to use OPC with MCPB.
> Thanks lot!
> --
> Gustavo Seabra.
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Received on Tue Sep 08 2020 - 06:30:02 PDT
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