Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 6, 2007
Publication Date: July 16, 2007
Citation: Barone, J.R., Dangaran, K.L., Schmidt, W.F. 2007. Protein-Transition Metal Ion Networks. Journal of Applied Polymer Science. 106:1518-1525.
Interpretive Summary: USDA-ARS has developed a novel class of polymers based on poultry feather keratin. Feather keratin is a protein composed of various amino acids. It is possible to elicit new properties from the protein by altering chemical groups on the amino acids in the protein. In this paper, chemical groups on the amino acids in feather keratin are altered using divalent transition metal ions. Cross-linking is observed manifesting as an increase in polymer stiffness. The effect of the divalent metal ion on chemical structure is elucidated using FT-IR spectroscopy and shows that the directed valence of the divalent transition metal ion interacts with carbonyls and amides on the protein and hydroxyls on glycerol.
Proteins obtained from agricultural sources were blended with divalent metal ions. Feather keratin, egg albumin, and wheat gluten showed increases of 2-3 times in modulus with addition of divalent transition metal ions Cu2+ and Zn2+. Increasing concentrations of ions resulted in increased stiffness. Birefringence experiments performed concurrently with tensile experiments showed refractive index changes indicative of network formation. Binding divalent alkaline earth metal Ca2+ ions did not result in a modulus increase. Addition of Zn2+ to egg albumin resulted in a 34% decrease in water permeability but no change in oxygen permeability. FT-IR spectroscopy showed that the directed valence of the transition metals was primarily binding glycerol and amide sites on the protein and secondarily carbonyl sites on the protein.