Contacts of a red guest residue at a mutant site i within a typical α-helix (a) and within an idealized α-helix in which local context effects are minimal (b). In (a), the red guest atoms contact the cyan neighboring backbone as well as side chain atoms of residues at (i ± 3) and (i ± 4) separations (green, magenta, orange, and blue circles). Both helical propensities and context effects are required to characterize the energetics of these interactions. For case (b), the contacts between side chains are minimal, and only the cyan contacts perturb helicity significantly. Their sequence-independent energetics are defined by the helical propensities.