Studio delle relazioni struttura-funzione in mutnti di emoglobina umana

We have obtained an experimental estimate of the free energy change associated with variations at the interface between protein subunits using five single and three double mutants of human Hb. A surprisingly good linear correlation between the change in the free energy of associ- ation of the mutants and the change in buried hydrophobic surface area was obtained, after corrections for the energetic cost of losing steric complementarity. Moreover, we have gained insight into the mechanism of discrimination between gaseous ligands inside the heme binding pocket by functionally and structurally studying three additional double mutants. One of these mutants may be considered as candidate for the synthesis of a possible ``blood substitute'', which should yield an O2 adduct stable to autoxidation and slowly reacting with NO.