Synthesis and Properties of High Molecular Weight Polypeptides Containing Proline

Abstract

Abstract High-purity N-carboxy-l-proline anhydride (N-carboxy-2-pyrrolidinecarboxylic acid anhydride) was synthesized. We used triethylamine instead of expensive Ag2O to remove HCl during the synthesis. Copolypeptides with a random sequence of l-proline (Pro) with glycine, l-alanine (Ala), l-α-aminobuthyric acid (Abu), l-Norvaline (Nva) or l-leucine (Leu) were synthesized by copolymerization of the corresponding N-carboxy-α-amino acid anhydrides in solution. Copolypeptides of Pro with Ala or Abu were partially soluble in water. However, the copolypeptides of proline with Nva or Leu with longer side chains were insoluble in water. The conformation of water-soluble copolymer at various pH was analyzed by circular dichroism (CD). The structures of the polypeptides in aqueous solution were almost independent of the pH, and were in a collagen-like conformation.