Synthesis of polypeptide models of elastin. Synthesis and properties of a cross-linked polytetrapeptide

Synthesis of two copolymers, H-(phi-Pro-Gly-Gly)n-Val-OMe and H-(phi'-Pro-Gly-Gly)n-Val-OMe, where phi is Val or Lys and phi' is Val or Glu is described. Cross-linking between the two copolymers is achieved by a coupling reaction between the epsilon-amino groups of the lysine containing copolymer and delta-carboxyls of the glutamic acid of the other copolymer. The cross-linking reaction was performed during a temperature elicited phase separation with flow orientation of the copolymers. Coacervation of the intermediate polymers is presented, as is the scanning electron micrograph of the insoluble cross-linked product and its calcifiability as determined with electron probe microanalysis. The purity of the key intermediates and polymers is demonstrated by the usual analytical methods. Carbon-13 magnetic resonance spectra of the intermediate monomer units are included to validate the purity of their synthesis.