AMBER Archive (2006)

Subject: AMBER: bugfix for frcmod.ff03 in Amber 9

From: David A. Case (
Date: Fri Jun 02 2006 - 11:45:29 CDT

There is a problem with the frcmod.ff03 file in Amber 9 that leads to bad
assignments of backbone torsions. A patch is available as bugfix.5 on the
Amber web site:

If you made a prmtop file using this file (e.g. by using leaprc.ff03), you
will have to re-run LEaP to create a new prtmop file.

If you are just using sander in Amber 9 to run simulations using a prmtop
file created in Amber 8, you are fine.

Thanks to Yong Duan for finding this problem, which was not his fault.

Apologies to those who may have been affected by this bug.

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