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P. George, J. Beetlestone and J. S. Griffith 



in order either of increasing or decreasing magnitudes, depending on the 

 particular wavelength. In the ultra-violet region, 330 to 450 m//, the trend 

 is not so clear-cut, but, as will be shown in the next section, this can be 

 attributed to the small but significant shift of all the ferrimyoglobin band 

 maxima relative to those for ferrihaemoglobin, together with systematically 



300 



250 



A(rTVj) 



Fig. 12. Ultra-violet spectra of ferrimyoglobin and ferrihaemoglobin hydroxide 

 in the region of tyrosine and tryptophane absorption (Hanania, 1953). 



lower extinction coefficients (see Fig. 8). In the region 250 to 300 mft no 

 strict evaluation is possible because myoglobin and haemoglobin are not 

 alike in tyrosine and tryptophane content. Nevertheless it is interesting that 

 the curve for ferrimyoglobin hydroxide, which has higher moment, in contrast 

 to that for ferrihaemoglobin with the lower moment, has a well-defined 

 shoulder at 290 m/u Hke the high-spin fluoride complex (see Figs. 9 and 12). 

 The data for ferriperoxidase are not quite suflficient for it to be included in 

 the sequence in equation (7), although there are ample indications that it 

 would fit into the pattern and come between ferrihaemoglobin hydroxide and 

 the low-spin cyanide complex. The magnetic moment has been determined 

 for horseradish peroxidase, 2-66 B.M. (Theorell, 1942), but the absorption 

 spectrum, recorded by Keilin and Hartree (1951) and reproduced in Fig. 10, 

 refers to a pH of 11-4, which, judging from the pK of 10-9-1 1-3, would give 



