A comparison of the different helices adopted by α- and β-peptides suggests different reasons for their stability

The right-handed alpha-helix is the dominant helical fold of alpha-peptides, whereas the left-handed 3(14)-helix is the dominant helical fold of beta-peptides. Using molecular dynamics simulations, the properties of alpha-helical alpha-peptides and 3(14)-helical beta-peptides with different C-terminal protonation states and in the solvents water and methanol are compared. The observed energetic and entropic differences can be traced to differences in the polarity of the solvent-accessible surface area and, in particular, the solute dipole moments, suggesting different reasons for their stability.