Resilin is an elastomeric
protein found in specialized regions of the cuticle of most insects, providing outstanding material properties including high resilience and
fatigue lifetime for insect flight and jumping needs. Two exons (1 and 3) from the
resilin gene in Drosophila melanogaster were cloned and the encoded
proteins expressed as soluble products in Escherichia coli. A heat and
salt precipitation method was used for efficient purification of the
recombinant proteins. The
proteins were
solution cast from water and formed into rubber-like
biomaterials via
horseradish peroxidase-mediated cross-linking. Comparative studies of the two
proteins expressed from the two different exons were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichrosim (CD) for structural features. Little structural organization was found, suggesting structural order was not induced by the
enzyme-mediated di-
tyrosine cross-links. Atomic Force Microscopy (AFM) was used to study the elastomeric properties of the uncross-linked and cross-linked
proteins. The
protein from exon 1 exhibited 90% resilience in comparison to 63% for the
protein from exon 3, and therefore may be the more critical domain for functional materials to mimic native
resilin. Further, the cross-linking of the recombinant exon 1 via the
citrate-modified photo-Fenton reaction was explored as an alternative di-
tyrosine mediated polymerization method and resulted in both highly elastic and adhesive materials. The
citrate-modified photo-Fenton system may be suitable for in vivo applications of
resilin biomaterials.