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Team:Cambridge/Project
From 2011.igem.org
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Contents |
Bactiridescence - Reflectin' the Future
Reflectins are a recently identified protein family rich in aromatic and sulphur-containing amino acids, responsible for the 'reflective' camouflage exhibited by certain cephalopods. To date, researchers have isolated the protein, over-expressed it in Escherichia coli and shown it to exhibit self-assembling behaviour and a changeable morphology which leads to dynamic manipulation of incident light.
Under in-vitro conditions Kramer et. al produced thin films, photonic gratings and fibres which exhibited structural colour extending across the entire visual spectrum by varying the thickness. In particular the colour change was demonstrated to be reversible. It is hypothesized the colouration is a result of thin film interference.
Within the Atlantic squid Loligo pealeii, Morse et.al found a multi-layer alternating structure of iridophore platelets of reflectin and an unidentified material, each possessing different refractive indices. By studying tissue samples in-vitro the researchers observed conformational changes in the multi-layer structure due to phosphorylation.
As part of our iGEM project we propose to express reflectin in-vivo within Escherichia coli to reproduce the same multi-layer structure. Further we wish to demonstrate the ability to dynamically tune structural colour in-vivo through phosphorylation. Our work will directly impact upon the design of next-generation novel biosensors.
Project Details
Reflectin and its Properties - A Summary of Our Research
In choosing our project we read all the papers we could find on reflectin and several on the squid species that have been worked on.
What species of squid have reflectin proteins?
Reflectin was initially identified in the Hawaiian bobtail Euprymna scolopes as the protein responsible for this species' iridescence and Reflectin 1a from E. scolopes has been successfully expressed in E.coli and purified (the interesting properties of this purified protein are discussed below). Related proteins in Lolliguncula brevis and squid of the genus Loligo have caused much research interest because these species appear to control their iridescence, a property called dynamic iridescence.
What purpose do reflectins have in these species? Reflectins are contained within stacks of repeating membranous structures with in cells in squid skin known as iridophores and together these structures and the reflectin proteins form natural Bragg reflectors (see below). Iridophores and other cell types with optical properties contribute to the squid's ability to camouflage itself and communicate with other animals via manipulating light, What is dynamic iridescence?
How does dynamic iridescence work in squid? (membrane association)
What is Bragg reflector?
What is known about the unsual amino acid content of reflectins?
What is known about the structure of the reflectin proteins?
What are the differences and conserved sequences between different reflectins and between reflectins in different species?
What work has been done on expressing reflectins in E.coli?
What in vitro experiments have been performed on reflectins?
What are the properties of in vitro films of reflectin?
1. Kramer et al. nature materials 533-538 VOL 6 JULY 2007
The Experiments
Part 3
Results
