Parallel
and T-shaped stacking interactions of the peptide plane
with polar and ionizable amino acid side chains (including aspartic/glutamic
acid, asparagine/glutamine, and arginine) are investigated using the
quantum mechanical MP2 and CCSD computational methods. It is found
that the electrostatic interaction plays an essential role in determining
the optimal stacking configurations for all investigated stacking
models. For certain complexes, the dispersion interaction also contributes
considerably to stacking. In the gas phase, the stacking interaction
of the charged system is stronger than that of the neutral system,
and T-shaped stacking is generally more preferred than parallel stacking,
with the stacking energy in the range of −4 to −18 kcal/mol.
The solvation effect overall weakens stacking, especially for the
charged system and the T-shaped stacking configurations. In water,
the interaction energies of different stacking models are comparable
