Figure 4: Surface representation of HSA (PDB 1ao6) showing the tunnel connecting the surface of the protein with the residues involved in the aldol condensation. In red, in stick representation, Lys 199 and Arg 222. In green, Arg 218 in the same cavity and spatially close to the residues mentioned before. In the entrance of the tunnel, we found a conserved positively charged residue (His, Lys, Arg) evolving under positive selection.