318 VII. COMPARATIVE BIOCHEMISTRY OF HEMOGLOBINS 



lysine ratio is 1:1:5:9:15, or 4:6:36:60, in horse myohemoglobin, which 

 should be compared with the ratio 4:14:33:37 which Vickery (2877) 

 gives for horse hemoglobin. Roche and co-workers {2315,2316,2321) 

 have investigated the myohemoglobin of a number of genera; values for 

 valine, tryptophane, arginine, and cysteine are approximately the same in 

 ox, horse, and dog, while variations are found in the tyrosine, leucine, alanine, 

 lysine, and histidine contents. In comparison with the hemoglobin of the 

 same genus, the muscle pigment is poorer in tyrosine, leucine, valine, and 

 arginine and richer in tryptophane, lysine, histidine, and cysteine, thus 

 confirming Rossi's findings. There are also immunologic differences between 

 the myohemoglobins and the homologous hemoglobins {1522a). 



5.3. Solubility 



Roche and Combette {2313) have measured the solubility of the erythro- 

 cruorins of Arenicola and Dasybranchus. In spite of the fact that measurement 

 of the osmotic pressure of the species with which they were working indicated 

 that the molecular weight of the Dasybranchus erythrocruorin (intracellular) 

 was only 26,200 and that of the Arenicola 362,000, there was little difference 

 in the concentration of ammonium sulfate required to salt them out. The 

 latter pigment was precipitated between 0.5 and 0.6 saturation and the 

 former between 0.55 and 0.7. 



Investigations of the mammalian pigments from erythrocytes and muscle 

 show the existence of generic differences within each class of pigment as well 

 as differences between the hemoglobins and the myohemoglobins. The data 



TABLE VIII 



Solubility Constants of Vertebrate Hemoglobins" 



" According to Roche and Derrien {2315). Determinations made in ammonium sulfate 

 at 21° C. 



of Roche and Derrien {2315) are shown in Table VIII. The solubility of the 

 pigments is given as a function of ionic strength according to Cohn's equation : 



log S = )8 - K',T/<i 



where S is the solubility in grams protein nitrogen per 100 ml. solution, 

 r/2 is the ionic strength in moles per liter, and K', is the apparent salting out 

 constant, the numerical value of which varies with the nature of the protein 



