92 B. KEIL [5 



ion exchanger. All other components of the mixture, including unreacted 

 peptide, are eluted. The DNP-peptide is then desorbed back into the flask, 

 evaporated to dryness and, after removal of the ion-exchanger, hydrolysed 

 in situ. The DNP amino acid is adsorbed on a fresh batch of the ion ex- 

 changer, the free amino acids being eluted. The adsorbed material is eluted 

 back into the flask, the dinitrophenol is removed by vacuum sublimation 

 and the residual DNP amino acid is identified by paper chromatography. 

 This procedure eliminates the extraction with organic solvents and the 

 separation into water-soluble and ether-soluble fractions. The technique, 

 which readily lends itself to work with whole series of samples, was used 

 for most of the peptides mentioned in Professor Sorm's paper. 



REFERENCES 



1. B. KEIL, Chem. Listy, 4S, 725 (1954); Coll. Czechoslov. Chem. Commun. 19, 1006 

 (1954). 



2. B. KEIL, Chem. Listy, 51, 1927 (1957); Coll. Czechoslov. Chem. Commun. 11, in press. 



3. o. MIKES, Chem. Listy, 51, 138 (1957); Coll. Czechoslov. Chem. Commun. 11, 831 



(1957). 



4. o. MIKES, J. VANÊCEK, B. MELOUN, v. KOSTKA and J. KARA, Chem. Listy, 

 51, 1562 (1957); Coll. Czechoslov. Chem. Commun. 11, in press. 



5. J. VANECEK, B. MELOUN and F. sORM, Chem. Listy, 51, 1367 (1957); Coll. 



Czechoslov. Chem. Commun. 11, in press. 



