ALKALI PROTEINS WITH LAPSE OF TIME 119 



unable to observe any alteration of the optical rotation with lapse 

 of time in glutin solutions in concentrations of alkali up to o-i N. 

 On the other hand, a very marked falling off of optical 

 rotation with time has been observed as a result of the alterations 

 of state which take place in clupein and in glutin (A. Kossel *) . 

 An explanation has been furnished by H. D. Dakin. f It is here 

 a question of the change from the keto to the enol form by the 

 action of strong alkali on the group : 



-CH 2 CH 



i. I ;= II ..... ii. 



-CO -C(OH) 



In this case an asymmetric carbon atom is concerned, so that, 

 as the following example (hydantoin) shows, an optically 

 inactive form II. results : 



i. 



R_C* 



NH . CO . NH NH . CO . NH 



I II 



co : i R C==C 



OH ii. 



Dakin's representation of the rearrangement shows the carbon 

 atom next the peptide linkage behaving as an asymmetric 

 carbon atom, but the formation of the hydroxyl group with acid 

 properties follows as in the lactim form in amino-acid chains. 

 For clearer comparison we give below the scheme of Leuchs of 

 the transformation at the peptide linkage and that of Dakin 

 of the change at neighbouring linkages in the case of a tripeptide. 



Leuchs. 



NH 2 . CH 2 . CO . NH . CH 2 . CO . NH 2 COOH ~ - 



I. Lactam. 



NH 2 . CH 2 C(OH) : N . CH 2 C(OH) : N . CH 2 COOH 



II. Lactim. 



Dakin. 



NH . CO . CHR 



.C 



R.C*H.CO.NH 



I. Keto form. 



NH 2 

 CHR 

 C 



NH 

 RC : 



CO . CH . R . NH 



OOH 



C . OH . NH . CH . R 



COOH 

 II. Enol form. 



* Zeitsch. physiol. Chem., 1909, 59, 492 ; 1909, 60, 311 ; 1910, 68, 165. 

 t Am. Chem. /., 1910, 44, 48 ; /. Biol. Chem., 1912, 19, 357. 



