modified residues (pyruvoyl)

[Gordon <>]

I've found the following works for pyruvoyl residues

top_heav.lib entry:
RESI PVL     0.00000
ATOM O2   O      -0.5500
ATOM C3   CD      0.5500
ATOM C2   CD      0.6000
ATOM O3   O      -0.5500
ATOM C1   CT3    -0.1500
DELE ATOM N
BOND O2 C2 C2 C1 C2 C3 C3 O3 C3 +N
IMPR C1 C2 C3 +N
IMPR O3 C3 C2 O2
IC O3    C3    C2    O2        1.2355  116.9032   15.0961  120.8798    
1.2270
IC C1    C3    C2    O2        1.5090  128.5815 -171.5204  120.8798    
1.2270
IC +N    O2    C2    C3        1.3535  122.1373  175.9258  120.8798    
1.4157
PATC FIRS NONE LAST NONE

restyp.lib entry:
142 | PVL                 | O | PVL  | pyruvoyl