AMINO ACID COMPOSITION AND ORDER 2^7 



pounds of the nature of conjugated proteins or extremely 

 ephemeral complexes which only have a very transient exist- 

 ence, as happens in the formation of intermediate compounds 

 (enzyme-substrate) . 



Arising from this, many students of proteins from H. 

 Ritthausen^" to present-day authors (e.g. H. B. Vickery^^ and 

 W. H. Stein''^) have put forward the suggestion that the 

 chemical, and even the physiological, characteristics of any 

 particular protein could be deduced from a detailed and 

 complete knowledge of its amino acid composition and an 

 understanding of the properties of the different amino acids 

 of which it is made up. 



Quantitative and qualitative analytical studies on various 

 proteins with a view^ to determining their amino acid com- 

 position have been going on for many years. However, the 

 methods devised in the classical works of A. Kossel, E. Fischer 

 and T. B. Osborne^^ and others depended on the separation 

 of amino acids from hydrolysates and involved the expendi- 

 ture of enormous amounts of effort, time and starting ma- 

 terials. For this reason such studies were very few and far 

 from complete. However, there have been introduced into 

 protein chemistry in recent years new and satisfactory micro- 

 methods based on up-to-date principles of investigation^'* 

 (isotope dilution^^ and the isotope-derivative method,^^ 

 microbiological assay^^ and chromatography^^). This led to 

 signal advances in the field of amino acid analysis and a very 

 large number of proteins may now be taken to have been 

 fully analysed in this respect. (The extensive factual material 

 is given in the numerous tables in the article by G. R. 

 Tristram. ^^) 



Detailed studies have also been made of the chemical 

 properties of the separate amino acids which are found in 

 proteins, those which are common to all carboxylic acids and 

 primary amines and also the specific functional attributes 

 which belong to each separate amino acid and characterise 

 its radical (R). The extensive data on this subject have been 

 recently collated in a review by P. Desnuelle.^^ 



The results obtained in this way were, however, rather 

 unexpected. In particular, it was found that only a very 

 limited number of different amino acids are to be found in 



