Ferrihaemoprotein Hydroxides 



ni 



hydroxide in Fig. 7 give the spectra for the high- and low-spin forms 

 shown in Fig. 18, which can be seen to have the expected features. The 

 high-spin form has well-defined bands at about 740 m^u with e^M = 0-9 

 and at 830 m/t with f^^ji = 1-15, which correspond closely to the bands for 

 the fluoride derivative: the low-spin form has scarcely any absorption 



'mM 



900 



800 

 A(m>i) 



700 



Fig. 18. Near infra-red spectra of the high- and low-spin hydroxides calculated 



from the data for ferrimyoglobin and ferrihaemoglobin hydroxide. 



No A or fniJVl corrections: /tj = 2-24, n^ = 5-92. 



throughout this region like the cyanide derivative (see Fig. 7). The small 

 negative extinction coefllicients actually obtained for the low-spin form can be 

 attributed to the uncertainties in the calculation procedure when the correction 

 factors are unknown, and also to experimental error. Precise extinction 

 coefficients are very difficult to determine in this region because the magni- 

 tudes are so small, and errors introduced by extraneous background absorp- 

 tion, which is hard to remove completely, become significant. 



Summary 



Assuming that the ferrihaemoprotein hydroxides are thermal mixtures, 

 and adopting /Uf^ = 5-92 and /tj = 2-24 as the magnetic moments of the 



