HP model: hydrophobic-polar lattice protein folding and contact energy
3D structure (2D lattice projection)
Contact map (residue pairs within 2Å)
HP Model (Lau & Dill 1989): Amino acids are classified as Hydrophobic (H) or Polar (P). On a 2D square lattice, the energy is the sum of contact energies for residue pairs that are adjacent on the lattice but not in sequence. Hydrophobic collapse drives H-H contacts to the protein core. The contact map shows all pairwise residue contacts — secondary structure (helices, sheets) appears as diagonal stripes. Folding energy minimization is NP-complete in general (Crescenzi et al. 1998), but Monte Carlo with Metropolis criterion finds good folds. Colors: orange = H (hydrophobic), blue = P (polar).