Figure 2

Decision tree classification of all observed substitutions for Leucines. Similar trees are built for each of the 21 residue types, including half-cystine. The structural environment for a given cluster is defined by the edge labels along its path from the root cluster c₀. For example, the nodes colored in gray indicate the partial classification path of a Leucine observed in a native structural environment whose descriptors s₂₃, s₁₅ and s₁₀ verify s₂₃ = pol = 3%, s₁₅ = pac = 7% and s₁₀ = d₄ = 5.4A.