Reversibly labile, sclerotization-induced elastic properties in a keratin analog from marine snails: whelk egg capsule biopolymer (WECB)

Egg capsules from two caenogastropod whelks, Busycon canaliculatum and Kelletia kelletii, were studied to investigate the genesis of mechanical properties of nascent capsules and to formulate a biomechanical model of this material. Scanning electron microscopy revealed that the capsules possess fibrous hierarchical arrangements at all stages during processing while the mechanical integrity is developing. This suggests that an as yet uncharacterized sclerotization mechanism occurring in the ventral pedal gland primarily binds these fibrous components together. Decomposing the mechanical behavior of WECB through various physical and chemical treatments led us to develop a model for the structure and mechanical properties of this material that supports its designation as a keratin analog. Keratin mechanical models were applied to WECB in its representation as an intermediate state between matrix-free intermediate filament (IF)-type proteins and the more complex composite materials incorporating IFs such as keratin.