Quantum Chemistry: Model Peptides

Peptides are mostly modeled by attaching a formyl or acetyl group to the N-terminus of a short peptide chain and by converting the C-terminus to an amide group at the same time. The peptide chain may be as small as a single residue X, in which case the model compound HCO-X-NH2 or CHCO-X-NH2 contains two peptide bonds and thus is called a model dipeptide. Model dipeptides can be used to study interactions of one amino acid residue with its next nearest neighbour (1-3-interactions) like gamma-turns; analogously, model tripeptides of the type HCO-X-Y-NH2 can be used to model 1-4-interactions like beta-turns.