Chemistry Between Cross-Links Determines the Properties of Protein Rubbers

Unlike synthetic rubbers, protein rubbers can have very high resiliency. Small or no thermodynamic losses make these materials interesting for many applications. Protein rubbers mimic real systems found in nature. The chemical diversity of different amino acids in proteins facilitates their modification. A simple nucleophilic addition reaction known as the Michael addition was used to add vinyl groups to amines and thiols in ovalbumin at standard conditions. Ovalbumin was first cross-linked with divinylsulfone (DVS) then sequences between cross-links were modified with acrylic acid (AA) or ethyl vinyl sulfone (EVS). Protein rubbers modified with AA were opaque while those modified with EVS were clear. Swelling properties of the two rubbers were different and an association model is presented to show the differences between the two protein rubbers based on the chemistry between cross-links.