| a, Structures of the src SH3 domain, 
      b, the wt a-spectrin SH3 domain and c, the distal 
      loop permutant, d, CI2 and e, the Arc repressor 
      dimer colored by FF value on a continuous scale from red 
      (1) to blue (0). The transition 
      state stability has a polarized patteern in the distal loop region, which 
      is out side of the hydrophobic core. While the transition state stability 
      is uniformly distributed around the hydrophobic core of CI-2 and Arc repressor. 
      (Figure adopted from Grantcharova et al., Natu. Struct. 
      Biol., 1998, 5(8):714) |