308 CHOH HAO LI [81 



an apparently pure peptide from pig pituitary glands, which they designated 

 Corticotropin-A. The following year Li and co-workers^^ at the University 

 of California reported the isolation, from a sheep ACTH concentrate that 

 had not been submitted to peptic digestion, of a peptide which behaves like 

 a pure substance. The California group designated this unhydrolyzed ACTH 

 obtained from sheep pituitaries a-corticotropin, since some of its chemical 



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2 6 10 14 18 22 26 30 34 38 



Segment Number (cm.) 



Fig. 3. Zone electrophoresis of beef /3-MSH {à-A) and a mixture of beef jS-MSH and 

 pig /S-MSH (o-o) on starch; pyridine-acetate buffer of pH 4-83 and 1= 01 ; 200 v for 24 

 hours. 



20 5 



Time. Hours 



Fig. 4. Action of leucine aminopeptidase on beef and pig jS-MSH; 0-6 mg. en2yme/l-4 

 mg. peptide; pH 8-1, 0-02 M Tris buffer containing 002 M-Mg++ at 40°C. 



