8

Chitinous Membranes and Analogous Material

113

where ε = ^L

Lo ^{= strain in the resilin.}

However, Eq. 7.6 can also be expressed as integral of Hooke’s law as

Ue =



kx.dx = ¹

2^kx2

(8.7)

The above mathematical expressions will help in understanding the physico-

mechanical properties of resilin, which are quite complex.

Structure of Resilin

Some parts of the insect cuticle undergo elastic deformations during locomotion. In

Fig. 8.3, the TS of wing hinge ligament of Schistocera gregaria has been enlarged by

using a light microscope. The relation of exocuticle to endocuticle to fibrous protein

and epidermis can clearly be seen. Resilin is found in between the two cuticle layers

and is in contact with the epidermis.

Resilin consists of a protein having 620 amino acid molecules long chain included

with a signal peptide of 17 residues at N-Terminus. This protein is secreted in the

extracellular space. Its relative molecular mass is 56,771 daltons and its isoelectric

point of 5.0 is composed of three domains. Resilin exhibits elasticity due to the cross

links, which are composed of dityrosine and trityrosine. It also possesses fluorescent

properties. Dityrosine, trityrosine and resilin emit a blue fluorescence when treated

by Ultraviolet (UV) light [11]. The elastic efficiency of resilin has been reported

from locust tendons by isolation of the protein. It is unaffected by deep freezing and

Fig. 8.3 Basic structure of wing hinge (TS) (modified after [3, 12])