title: Photoprotection by silk cocoons.
abstract: A silk cocoon protects a silkworm during its pupal stage from various threats. We systematically investigated the role of fiber, sericin, and embedded crystals in the UV protection of a silk cocoon. Diffuse reflectance and UV absorbance were measured and free radicals generated during exposure to UV radiation were quantified using photoinduced chemiluminescence (PICL). We identified the response to both UV-A and UV-B radiations by silk materials and found that sericin was primarily responsible for UV-A absorption. When sericin was removed, the photoinduced chemiluminescence intensity increased significantly, indicating higher UV-A-induced reactions of cocoons in the absence of sericin. There is progressively higher sericin content toward the outer part of the cocoon shell that allows an effective shield to pupae from UV radiation and resists photodegradation of silk fibers. The study will inspire development of advanced organic photoprotective materials and designing silk-based, free-radical-scavenging antioxidants.
authors.affiliation: Australian Future Fibres Research and Innovation Centre, Institute for Frontier Materials, and §CSIRO Materials Science and Engineering, Geelong Technology Precinct, Deakin University , Geelong, VIC 3216, Australia.
authors.forename: Jasjeet
authors.initials: J
authors.lastname: Kaur
authors.forename: Rangam
authors.initials: R
authors.lastname: Rajkhowa
authors.forename: Takuya
authors.initials: T
authors.lastname: Tsuzuki
authors.forename: Keith
authors.initials: K
authors.lastname: Millington
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Xungai
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D008163:Luminescent Measurements; D009036:Moths / Q000737:chemistry*; D010316:Particle Size; D055668:Photochemical Processes; D011835:Radiation Protection; D047011:Silk / Q000737:chemistry*; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D047011:Silk