In butterfly wing scales, chitin is organized into stacks of gyroids constructed of chitin photonic crystals that produce various iridescent colors serving phenotypic signaling and communication for mating and foraging. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry. Scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales (five to fifteen micrometres thick) that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, which serve to scatter light. The multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some social wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes, composed of paper.
The immune response can sometimes clear the chitin and its associated organism, but sometimes the immune response is pathological and becomes an allergy; allergy to house dust mites is thought to be driven by a response to chitin.
Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1 and chitin elicitor-binding protein. The first chitin receptor was cloned in 2006. When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, which in turn activate systematic defenses.Commensal fungi have ways to interact with the host immune response that as of 2016[update] were not well understood.
Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors.Zymoseptoria tritici is an example of a fungal pathogen that has such blocking proteins; it is a major pest in wheat crops.
Chitin was probably present in the exoskeletons of Cambrian arthropods such as trilobites. The oldest preserved chitin dates to the Oligocene, about 25 million years ago, consisting of a scorpion encased in amber.
Chitin is used in industry in many processes. Examples of the potential uses of chemically modified chitin in food processing include the formation of edible films and as an additive to thicken and stabilize foods. Processes to size and strengthen paper employ chitin and chitosan.
How chitin interacts with the immune system of plants and animals has been an active area of research, including the identity of key receptors with which chitin interacts, whether the size of chitin particles is relevant to the kind of immune response triggered, and mechanisms by which immune systems respond. Chitin and chitosan have been explored as a vaccine adjuvant due to its ability to stimulate an immune response.
^Auguste Odier (presented: 1821 ; published: 1823) "Mémoire sur la composition chimique des parties cornées des insectes" (Memoir on the chemical composition of the horny parts of insects), Mémoires de la Société d'Histoire Naturelle de Paris, 1 : 29-42. From page 35: "... la Chitine (c'est ainsi que je nomme cette substance de chiton, , enveloppe) ..." (... chitine (it is thus that I name this substance from chiton, , covering) ...)
^Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia. See:
A. Hofmann (1929) "Über den enzymatischen Abbau des Chitins und Chitosans" (On the enzymatic degradation of chitin and chitosan), Ph.D. thesis, University of Zurich (Zurich, Switzerland).
P. Karrer and A. Hofmann (1929) "Polysaccharide XXXIX. Über den enzymatischen Abbau von Chitin and Chitosan I," Helvetica Chimica Acta, 12 (1) : 616-637.
Nathaniel S. Finney and Jay S. Siegel (2008) "In Memorian: Albert Hofmann (1906-2008)," Chimia, 62 (5) : 444-447 ; see page 444. Available on-line at: University of Zurich
^Campbell, N. A. (1996) Biology (4th edition) Benjamin Cummings, New Work. p.69 ISBN0-8053-1957-3
^Gilbert, Lawrence I. (2009). Insect development : morphogenesis, molting and metamorphosis. Amsterdam Boston: Elsevier/Academic Press. ISBN978-0-12-375136-2.
^Kudô, K. Nest materials and some chemical characteristics of nests of a New World swarm-founding polistine wasp, (Hymenoptera Vespidae). Ethology, ecology & evolution 13.4 Oct 2001: 351-360. Dipartimento di biologia animale e genetica, Università di Firenze. 16 Oct 2014.
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^ abSharp, Russell G. (21 November 2013). "A Review of the Applications of Chitin and Its Derivatives in Agriculture to Modify Plant-Microbial Interactions and Improve Crop Yields". Agronomy. 3 (4): 757-793. doi:10.3390/agronomy3040757.
^Rovenich, H; Zuccaro, A; Thomma, BP (December 2016). "Convergent evolution of filamentous microbes towards evasion of glycan-triggered immunity". The New Phytologist. 212 (4): 896-901. doi:10.1111/nph.14064. PMID27329426.