Monte Carlo simulations of polyalanine using a reduced model and statistics-based interaction potentials.

A coarse-grained residue-residue interaction potential derived from a statistical analysis of the Protein Data Bank is used to investigate the coil-to-helix transition for polyalanine. The interaction potentials depend on the radial distance between interaction sites, as well as the relative orientation of the sites. Two types of interaction sites are present in the model: a site representing the amino acid side chain, and a site representing a "virtual backbone," i.e., a site located in the peptide bond which accounts for backbone hydrogen bonding. Two chain lengths are studied and the results for the thermodynamics of the coil-to-helix transition are analyzed in terms of the Zimm-Bragg model. Results agree qualitatively and quantitatively with all-atom Monte Carlo simulations and other reduced-model Monte Carlo simulations.