Fenihaemoprotein Hydroxides 



117 



Now the regular and systematic differences between the spectra of high- 

 and low-spin complexes suggest very strongly that if the hydroxides are 

 mixtures of high- and low-spin forms their spectra and magnetic moments 

 should conform to a certain pattern. 



(a) For the same haemoprotein, the extinction coefficients for the hydroxide 

 should be intermediate in value between those for typical high- and low-spin 

 complexes in the regions where the major absorption bands occur. 



(b) For a series of hydroxides, there should be a regular trend in the extinc- 

 tion coefficients in the region of the major absorption bands, such that the 



450 



400 



350 



300 



A(mjj) 



Fig. 11. 



Ultra-violet spectra of ferrimyoglobin and ferrihaemoglobin hydroxide 

 (Hanania, 1953). 



higher magnetic moment hydroxides resemble more closely the high-spin 

 complexes, and the lower magnetic moment hydroxides resemble more 

 closely the low-spin complexes. 



In the case of ferrimyoglobin, the only haemoprotein for which complete 

 data are available at present, the first criterion is found to hold throughout 

 the entire range of wavelength, 250 to 950 m/<. For the visible region the 

 myoglobin curve in Fig. 10 is to be compared with those in Figs. 5 and 6; 

 Fig. 7 covers the region 700 to 950 m/t ; Figs. 8 and 1 1 give the Soret bands, and 

 the smaller bands in the region 330 to 370 m/i ; and Fig. 9 covers the region of 

 composite absorption, 250 to 300 m//. The second criterion is borne out by 

 a comparison of the spectra of ferrimyoglobin and ferrihaemoglobin hy- 

 droxides in Figs. 7 and 10, where the extinction coefficients follow the sequence 



Fluoride Complex -» FerriMb Hydroxide -* FerriHb Hydroxide -> Cyanide Complex (7) 

 high spin 5-11 B.M. 4-47 B.M. low spin 



