Excerpt - page 55: "... chosen for the formation of 34 different structures of di-, tri-, and tetrapeptides. These amino acids had been known for their probable presence in prebiotic ..."
Excerpt - page 91: "... a series of peptides composed of methionine and one other amino acid, or of di-, tri-, and tetrapeptides in which the position of the substituent is ..."
Excerpt - page 186: "... ANALYSIS [331 [33] Penicillamine By ELISABETH M. WOLF-HEUSS Introduction D-Penicillamine (2-amino-3-mercapto-3-methylbutanoic acid) is a tri- functional thiol amino acid. ..."