Fenihaemoprotein Hydroxides 



115 



345 and 360 mfi can be distinguished in the case of the cyanide complex. At 

 shorter wavelengths, from 260 to 300 m/i, absorption due to both the ferri- 

 porphyrin prosthetic group and tyrosine and tryptophane residues in the 

 protein occurs, as evidenced by the greater absorption of the ferrihaemo- 

 proteins as compared to their apo-proteins. As shown in Fig. 9 the low-spin 



450 



400 



350 



300 



7\(m>i) 



Fig. 8. 



Ultra-violet spectra of ferrimyoglobin and ferrihaemoglobin cyanide 

 and fluoride (Keilin and Hartree, 1951; Hanania, 1953). 



cyanide derivative has greater absorption than the high-spin fluoride deriva- 

 tive throughout this region, although the band at 290 m/( is less well resolved. 

 While the spectra of the high- and low-spin derivatives exhibit these 

 characteristic distinguishing features, which as far as can be judged are 

 common to myoglobin, haemoglobin and peroxidase, the spectra of the 

 hydroxides vary a great deal as shown in Figs. 7, 10, 1 1 and 14. Moreover 

 these variations are not haphazard, but appear to be related to the change in 

 magnetic moment, i.e. 



FerriMb -^ FerriHb -> FerriPer (5) 



5-11 B.M. 4-45 B.M. 2-66 B.M. 



To take but one example, in the region of 600 m/<, the extinction coefficients 

 follow the order 



as shown in Fig. 10, 



'Mb 



> £Hb > e 



Per 



(6) 



