250 



VI. HEMOGLOBIN 



4.2.2. Globin and Cleavage Products of Hemoglobin. Boyes- 

 Watson and Perutz suggest that the four layers, 9 A apart, which 

 they observe in the crystal may each consist of four folded polypeptide 

 chains extending in the direction of the b axis. The splitting of the 

 hemoglobin molecule would therefore be unlikely to occur in the b 

 plane, since this would involve the rupture of peptide bonds within 

 the chain. Splitting is therefore most likely in the a or c planes, and 

 would involve the breakage of bonds between the polypeptide chains. 

 While cleavage in the b plane would have produced halves no more 

 asymmetric than the original molecule, the half molecules produced 

 by cleavage in the a or c planes would be more asymmetric. This is 

 illustrated in the accompanying diagram (Fig. 5). If the molecule is, 

 however, a circular disc, as now suggested by Perutz, splitting in the 

 a plane would not yield a more asymmetric molecule. 



Splitting in the a plane Splitting in the c plane 



Fig. 6. Dissociation of the hemoglobin molecule into half-molecules. 



Gralen (1028) subjected globin to analysis in the ultracentrifuge 

 and in Lamm's diffusion cell. The results indicated the presence of 

 fragments of different sizes, the largest of which corresponded to a 

 molecular weight of 37,000. The frictional ratio was found to be 

 greater than that of hemoglobin, which he interpreted as indication 

 of a more asymmetric molecule. Neurath {20If5), on the other hand, 

 has interpreted Steinhardt's results {2JtS7) on the dissociation of 



