9] MYOGLOBIN I 143 



From a practical point of view, the above results lead to some limitations 

 in the use of the crystalline pigment in future research on myoglobin. Studies, 

 also with spectrophotometric methods, on the equilibrium between human 

 Mb and O2, can be properly based on non-homogeneous crystalline pigment, 

 whilst in any research on the structure of myoglobin homogeneous prepara- 

 tions must be used. 



Research still in progress in our Laboratory leads us to think that human 

 Mb I and Mb II have different chemical structures. 



REFERENCES 



1. A. Rossi-FANELLI and E. ANTONiNi, Arch. Biochem. and Biophys., 65, 587 

 (1956). 



2. o. SMITHIES, Biochem. J., 61, 629 (1955). 



3. A. ROSSI-FANELLI and E. ANTONINI. In press. ^^cpenV/j/Zo. 



