Structure of thermal polymers of amino acids.

When glutamic acid is a predominant amino acid in a thermally polymerized mixture of amino acids, pyro Glu is exclusively found at the N-terminal end of the poly-amino acid polymer. It probably initiates the polymerization process. Lysine-containing polymers will probably contain epsilon N-(glutamyl)L-lysine cross links which may account for the higher molecular weights observed in these polymers (100-200 000). Incorporation of some amino acids facilitates the incorporation of others. When utilizing mixtures of three to eight amino acids with glutamic acid as one of the amino acids, some fractions are obtained which include all the amino acids in the polymerization mixture. The biosynthesis of glutathione, gramicidin, tyrocidine and cell-wall polypeptides has demonstrated that non-random amino acid sequence peptides can be biologically synthesized without the direct participation of nucleic acids. That is, the enzymes appear to provide adequate chemical specificity to form non-random amino acid sequence peptides. The properties and replication of the scrapie agent may provide us with more profound insight as to the evolution of purely physical-chemical systems into biological systems.