Ultimately, models which explicitly capture all atoms and their physical interactions are required to study the folding of real proteins.
since such models often require huge computational resources such as supercomputers or distributed systems, novel search strategies and other general properties of the folding problem are usually first studied with coarse-grained, simplified representations, such as the HP model (Lau and Dill, 1989;Dill et al., 1995) used here.