Synthesis and characterization of elastin-mimetic protein gels derived from a well-defined polypeptide precursor

To elucidate the effects of uniformity of molecular architecture on gel pro perties, a protein polymer based on the elastin-mimetic repeat sequence [(V al-Pro-Gly-Val-Gly)(4)(Val-Pro-Gly-Lys-Gly)], 1 (Lys-25), was synthesized u sing genetic engineering and microbial protein expression. The regularly pl aced lysine residues in poly(Lys-25) underwent selective reaction with elec trophilic cross-linkers under mild conditions in either dimethyl sulfoxide or aqueous phosphate buffer to afford solvent-swollen networks. Chemical de rivatization and spectroscopic investigations of the cross-linking reaction indicated that approximately 85% of the lysine residues reacted with the c ross-linker. The protein hydrogel exhibited reversible, temperature-depende nt expansion and contraction with an estimated midpoint temperature for the phase transition at 35 degrees C. Scanning electron microscopy (SEM) inves tigations indicated profound differences in morphology between protein gels prepared in organic vs aqueous solution.