96 



Albert I. Lansing 



Table II 



Amino Acid Composition of Young Light and Old Heavy Elastin 



♦This preparation contained 1 • 14 per cent calcium and 14-9 per cent N, 

 fThis preparation contained 6-39 per cent Ca and 12-5 per cent N. 



These data indicate that the amino acid composition of 

 young and old arterial elastin is significantly different. 



It is doubtful that the shift in amino acid distribution 

 represents a change with time in the amino acid composition 

 of a pure protein. The elastin studied may be a mixture of 

 two or more proteins, and the changes observed may be 

 related to differences in the ratios of the separate constituents. 

 How such a change can come about is not yet known. It is 

 possible that the proteins laid down later in life may be 

 difPerent from those formed earlier because they are formed 

 under the influence of fibroblasts which themselves have 

 undergone age changes. 



