IX. GENETICS AND HUMAN HEMOGLOBIN CHEMISTRY 



413 



It is beyond the purpose of this review to give a full account of the 

 veiy specialized chemical methods that have been used to study the 

 amino acid sequence of the hemoglobin chains. The peptide chains have 

 been separated by column chromatography, according to Wilson and 

 Smith (1959), or by countercurrent distribution (Hill and Craig, 1959). 

 Hydrolysis by means of proteolytic enzymes has been used to degrade 

 the peptide chains to small peptides. Trypsin was the first choice because 

 tiypsin specifically cleaves the peptide bonds between the carboxyl group 

 of lysine or arginine and the amino group of other amino acids. The 

 separation and purification of the tiyptic peptides (peptides obtained 



TABLE I 



Tryi'tic Peptides of the a and /3 Chains of Hb-A 



" Peptide numbers refer to Fig. 2B, according to Ingram (1958). Two peptides are 

 present in each of the spots 16, 20, and 21, one from the a chain and one from the /3 

 chain. Peptide 17/3 overlaps with peptide 15a in Fig. 2. 



* The tryptic peptides are numl)ered consecutively from the N-terminus in each chain 

 (Gerald and Ingram, 1961). Peptide 22 happens to be free Ij^sine. The identification of 

 the tr.yptic peptides and the correspondence with the amino acid sequence of the peptide 

 chains (Braunitzer et al., 1961b; Konigsberg et al., 1961) are based on the amino acid 

 composition and/or sequence of the peptides (quoted by Baglioni, 1961). Preliminary 

 evidence exists for the identification of peptides a, b, and c; analysis of peptide e (Fig. 2) 

 gives only b'sine (C. Baglioni, unpublished). Peptide e may possibly be lysyl-lysine. 



" Peptide 24 is identical with peptide 25, except that the methionine residue in this 

 peptide has become oxidized. 



