from Simmerling, Strockbine, Roitberg, JACS 124:11258, 2002.  Modifies parm99.
MASS

BOND

ANGL

DIHEDRAL
N -CT-C -N    1    0.700       180.000          -1.
N -CT-C -N    1    1.100       180.000           2.
C -N -CT-C    1    1.000         0.000           1.

NONB