Often the complexity of the problems in analysis/design of structures grow at an exponential rate. Redesign of a small protein (80 residues): 10^115^ Changing the (hydrophobic) core of a protein (170 residues): 10^224^ Side-chain placement on a protein backbone (2462 residues): 10^1044^ (*) From: Looger, L.L. and Hellinga, H.W. "Journal of Molecular Biology", 2001, 37, 429-445.