"Classical direct dynamics simulations were performed using VENUS/MOPAC, with the RM1 and AM1 semiempirical electronic structure theory as implemented in MOPAC, to study the unimolecular dissociation of the TIK(H
+)
2 tripeptide. Ensembles of trajectories were randomly excited at temperatures of 1250, 1500, 2000, and 2500 K, corresponding to classical energies in the 1778−3556 kJ/mol range. Temperature effect on primary fragmentation athways were studied. "