Incorporation of pairwise interactions into the Lifson‐Roig model for helix prediction

The helix/coil equilibrium of a peptide in solution can be modulated by a variety of side‐chain interactions that are not incorporated into the standard statistical mechanical models for prediction of peptide helical content. In this report, we describe a recursive formulation of the Lifson‐Roig model that facilitates incorporation of specific pairwise side‐chain interactions as well as nonspecific individual side‐chain capping interactions. Application of this extended model to a series of host/guest peptides indicates that the apparent AG value for a pairwise apolar interaction is dependent upon the spacing and orientation but not the sequential location of the participating residues. The apparent AG values for such interactions are about 40% greater than the corresponding apparent ΔΔG values obtained from difference measurements.