Hydrophobic-Polar (HP) model on a 2D square lattice. Hydrophobic (H, red) residues gain energy from non-covalent contacts. Monte Carlo search finds low-energy conformations. The energy landscape is rugged — even this toy model is NP-hard to optimize.
Sequence
Current Energy: 0
Best Energy: 0
Max H-H contacts = minimum energy. Native state has most buried H residues.