510 530 550 520 



540 560 

 A, m// 



540 560 580 600 

 X, xw/x 



Fig. 1, Spectra of compounds of haems with bases. The haems (2 X 10~^m) 

 were dissolved in 0-01 n NaOH; samples were reduced with dithionite imme- 

 diately before adding the ligands and measuring the absorption spectra on 

 the Beckman DU Spectrophotometer. Ligands were added in excess, higher 

 concentrations causing no further change in absorption, in the following 

 molarities : 



P. pyridine 



1. hydrazine 



2. ethanolamine 



3. «-propylamine 



4. dimethylamine 



Mesohaem 



3-41 

 0-488 

 0-655 

 0-282 

 15-06 



Proto- and 

 2 : 4-diformyl haems 



3-41 

 0-195 

 0-301 

 0-159 

 15-06 



510 530 550 520 540 560 580 



A, m// A, m^ 



Fig. 2. Spectra of mercaptoethanol-haem compounds. The haem solutions 

 and the procedure were as described in Fig. 1, The ligand concentrations 

 were(M): pyridine (P), 3-41 ; ethanol (E), 8-5; mercaptoethanol (ME), 3-45. 



H.E. — VOL. I — G 



