AMBER Archive (2004)

Subject: AMBER: antechamber - improper torsions

From: Oliver Hucke (
Date: Tue Jul 20 2004 - 11:23:02 CDT

Dear All,

I am using antechamber for the preparation of the amber input files for
various small molecules. I noticed that for many sp2 atoms no improper
torsions are present neither in gaff.dat nor in the frcmod file obtained
with parmchk. Leap does not complain but I can find several warnings
like the following in the leap.log file when I load these molecules:

No sp2 improper torsion term for c2-ha-c2-c3
No sp2 improper torsion term for ca-ha-ca-ca

Can I ignore these warnings or should I add impropers for each sp2 atom?
I was thinking of using the following entry in parm99.dat as a template:

X -X -CA-HA 1.1 180.0 2.

I would appreciate very much your comments on this!

Thanks a lot,



Oliver Hucke, Dr. Health Sciences Building - K418C University of Washington 1959 NE Pacific St. Dept. of Biochemistry phone: (206) 685 7046 Box 357742 fax : (206) 685 7002 Seattle, WA 98195-7742 email: _______________________________________________________________

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