Studies on the determination of amino acids in protein hydrolysates - a new micro-colorimetric method for the determination of lysine.

The methods for determining the lysine content of purified proteins are still not entirely satisfactory, notwithstanding the many investigations which have been made since Osborne and Mendel(1) in 1914 first demonstrated its essential role in metabolism. Furthermore, our knowledge of the biochemistry of lysine has been impeded by the lack of reliable methods of analysis. For instance, nutritional studies would be greatly facilitated by the elaboration of a sensitive micromethod for the rapid determination of lysine in crude plant and animal tissues and in biological fluids. Available methods for the determination of lysine may be classified into three groups, (a) isolation procedures, (b) nitrogen distribution methods and (c) biological assays. In the following historical review of the development of these analytical procedures, it will be necessary to refer in detail to the determination of arginine and histidine since the methods for estimating these basic amino acids are so intimately connected one with the other