Re: [AMBER] multi source calls in tleap

From: Matias Machado <>
Date: Thu, 11 Feb 2021 10:52:23 -0300 (UYT)

Dear Alan,

These feature is present since AMBER 16 or so (at leat that is the oldest version I've tied)...

I don't think it is a bug, but Dave should certainly know better that me...

I think it is some kind of safe-lock to prevent users from doing potentially wrong things... such as over-witting force fields...

Indeed, oldff/leaprc.ff99SB and oldff/leaprc.ff99bsc0 load almost the same stuff, but for the bsc0 parameters of DNA.

Hence the right way to load the force field is just "source oldff/leaprc.ff99bsc0"

Anyway, as David mention, both the parameters and the way to load them are very old fashion...

One proper way to do it at present is:

source leaprc.protein.ff14SB
source leaprc.water.tip3p
source leaprc.DNA.bsc1



PS: I'm stating to use "leaprc.water.opc" and OP3 (OPC3) water model, which is much better than TIP3P for the same price :-P

----- Mensaje original -----
De: "David A Case" <>
Para: "AMBER Mailing List" <>
Enviados: Lunes, 8 de Febrero 2021 11:50:07
Asunto: Re: [AMBER] multi source calls in tleap

On Sun, Feb 07, 2021, Alan wrote:

>I've only noticed that now in ambertools 2020, perhaps that happened years
>ago, but my tleap scripts used to have:
>source oldff/leaprc.ff99SB
>source oldff/leaprc.ff99bsc0

>Which now throws an error.

Looks like a bug to me. I've submitted a fix for the upcoming AmberTools21.
Thanks for the report.

Is there a command to "unload" or "unsource" loaded parameters?


>For now I've just broken my one script in several scripts, which is fine
>but, still, it would be nice to know more about it.

Just hoping here that you have a good reason to be using such outdated force


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