Abstract
Summary
Twelve amino acids had proved essential for the survival and growth of both the mouse fibroblast (strain L) and a human carcinoma cell (strain HeLa). In media lacking a single essential amino acid; in which the cells would otherwise degenerate and die, normal growth and multiplication were obtained on the addition of a dipeptide containing the essential amino acid. The effective concentrations of the dipeptide were of the same order of magnitude as those required of the simple amino acid. It remains to be seen whether the dipeptide is incorporated into cellular protein as such, or whether it is first split into its component amino acids(3).
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