Thermodynamics of α- and β-structure formation in proteins

An atomic protein model with a minimalistic potential is developed and then tested on an α-helix and a β-hairpin, using exactly the same parameters for both peptides. We find that melting curves for these sequences to a good approximation can be described by a simple two-state model, with parameters that are in reasonable quantitative agreement with experimental data. Despite the apparent two-state character of the melting curves, the energy distributions are found to lack a clear bimodal shape, which is discussed in some detail. We also perform a Monte Carlo-based kinetic study and find, in accord with experimental data, that the α-helix forms faster than the β-hairpin.