PROTEINS 91 



method is inaccurate for cystine and has not yet been adapted for use with biolog- 

 ical fluids other than solutions of protein hydrolysis products formed by acid or 

 tryptic hydrolysis. 



Method of Kober and Sugiura. 1 Kober and Sugiura have devised micro- 

 chemical methods for the determination of a and j3-amino acids and certain deriva- 

 tives in products of protein hydrolysis and other mixtures based upon the property 

 of these amino acids and derivatives of dissolving cupric hydroxide quantitatively 

 in neutral or slightly alkaline solution. The reaction is said to be very rapid and 

 sensitive. See original articles for details. 



1 Kober and Sugiura: J. Am. Ch. Soc., 35, 1546, 1913. 

 Kober: /. Ind. Eng. Ch., 9, 501, 1917. 



