342 Mr. R. H. A. Plimmer [April 8, 



IV. — Heterocyclic Acids. 



Proline CH,-CH, 

 II 



CH, CH.COOH 

 \V 

 NH 



Hydroxyproline HO.CH-CH, 



CH 2 CH.COOH 



\V 



NH 



V. — Mono-amino Acids with Aromatic Nucleus. 



Phenylalanine C 6 H 5 . CH 2 . CH(NH 2 ) . COOH 

 Tyrosine HO . C G H 4 . CH 2 . CH(NH 2 ) . COOH 



VI. — Mono-amino Acid with Indole Nucleus. 



Tryptophan C-CH 2 .CH(NH 1 ).COOH 



/ ^ 



C e H 4 CH 



\ / 



NH 



VII. — Hexone Bases, or Di-amino Acids. 



Lysine H 2 N . CH 2 . CH 2 . CH 2 . CH 2 . CH(NH 2 ) .COOH 



/NH 2 

 Ar^inine HN = C 



X NH . CH 2 . CH 2 . CH 2 . CH(NH 2 ) . COOH 

 Histidioe CH 



// \ 

 N NH 

 I \ 



HC = C - CH 2 . CH(NH 2 ) . COOH 



VIII. — Thio-amino Acid. 



Cystine HOOC . CH(NH 2 ) . CH 2 S - SCH 2 . CH(NH 2 ) . COOH 



The chemical analysis of the proteins shows that the various 

 proteins yield different amounts of the amino acids. Some of the 

 data are shown in Table I. The chief peculiarity is pointed out by 

 enclosing the figure in a square. In general, the albumin group of 

 proteins contains all the amino acids, except glycine, in various 

 proportions. The globulin group is similar, but contains glycine, 

 and has in addition a higher amount of glutamic acid, especially 

 those globulins of vegetable origin. The phosphoproteins resemble 

 the albumins with no striking preponderance of any single amino 

 acid. The gliadin group of cereal proteins is peculiar in its high 

 content of glutamic acid and proline. The members of the sclero- 

 protein group (horn, hair, gelatin) are heterogeneous ; and here we 

 may note that silk fibroin is composed mainly of three mono-amino 

 acids, and is the very antithesis of sturin (the protein of fish sperm), 

 which is made up of the tlrree hexone bases with no or very little 



