"
Team:Cambridge/Project
From 2011.igem.org
Felix Zhou (Talk | contribs) (→Reflectin and its Properties - A summary of our literature review) |
Felix Zhou (Talk | contribs) (→What is Bragg reflector?) |
||
| Line 46: | Line 46: | ||
Bragg reflectors are structures of alternating layers of materials with different refractive indices. These structures dominantly reflect at a certain peak wavelength in relation to the individual separation of the layers. Each boundary layer exhibits partial reflection which through superposition lead to interference phenomena. The peak reflected wavelength is 4 times the spacing distance between layers whereby the path difference is such as to allow constructive interference. This is the fundamental principle behind thin film interference, responsible for the rainbow colours reflected by oil droplets on the surface of water and that present on soap films. | Bragg reflectors are structures of alternating layers of materials with different refractive indices. These structures dominantly reflect at a certain peak wavelength in relation to the individual separation of the layers. Each boundary layer exhibits partial reflection which through superposition lead to interference phenomena. The peak reflected wavelength is 4 times the spacing distance between layers whereby the path difference is such as to allow constructive interference. This is the fundamental principle behind thin film interference, responsible for the rainbow colours reflected by oil droplets on the surface of water and that present on soap films. | ||
| - | ====What is dynamic iridescence and does work in squid?==== (membrane association) | + | ====What is dynamic iridescence and does work in squid?==== |
| - | Iridescence describes material colour change as the viewing angle or the angle of incidence of light is varied. However dynamic iridescence observed in certain squid genera is believed to be a result of neural control. Specifically, the application of the neurotransmitter Acetyl Choline (ACH) to fresh skin samples resulted in detectable post-translational modifications of the protein, namely phosphorylation. It is believed that phosphorylation of reflectin proteins cause changes in the chemical interactions within the nanoparticles reflectin forms in-vivo within the iridophore. These changes subsequently induce an alteration in the volume of protein platelets of reflectin and critically the thicknesses of reflectin layers in the iridophore. The path difference between incident light on individual layers is thus altered resulting in a shift in peak reflected wavelength and therefore colour. | + | (membrane association) |
| + | Iridescence describes material colour change as the viewing angle or the angle of incidence of light is varied. However dynamic iridescence observed in certain squid genera is believed to be a result of neural control. Specifically, the application of the neurotransmitter Acetyl Choline (ACH) to fresh skin samples resulted in detectable post-translational modifications of the protein, namely phosphorylation. It is believed that phosphorylation of reflectin proteins cause changes in the chemical interactions within the nanoparticles reflectin forms in-vivo within the iridophore. These changes subsequently induce an alteration in the volume of protein platelets of reflectin and critically the thicknesses of reflectin layers in the iridophore. The path difference between incident light on individual layers is thus altered resulting in a shift in peak reflected wavelength and therefore colour. | ||
====What is known about the nucleotide sequence of reflectins?==== | ====What is known about the nucleotide sequence of reflectins?==== | ||
Revision as of 23:39, 19 July 2011
| You can write a background of your team here. Give us a background of your team, the members, etc. Or tell us more about something of your choosing. | File:Cambridge logo.png 200px |
|
Tell us more about your project. Give us background. Use this is the abstract of your project. Be descriptive but concise (1-2 paragraphs) | File:Cambridge team.png Your team picture |
| Team Example |
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 literature review
In choosing our project we research all the papers we could find on reflectin and several on the squid species that have been studied.
What species of squid have reflectin proteins?
Reflectin was first identified in the Hawaiian bobtail Euprymna scolopes as the protein responsible for this species' iridescence. Reflectin 1a from E. scolopes has been successfully expressed in E.coli and purified (1 ##create link##) (the interesting properties of this purified protein are discussed below). Related proteins in Lolliguncula brevis and in squid of the genus Loligo have attracted much research interest due to their ability to actively control their iridescence, a property termed dynamic iridescence.
What purpose do reflectins have in these species?
Reflectins are contained within stacks of repeating membranous structures known as iridophores within cells in squid skin. Within these structures, the reflectin proteins self-assemble to form a natural 'Bragg stack' (see below ##insert link##). Along with other cell types with optical properties these Bragg stacks contribute to the squid's ability to camouflage itself and communicate with other animals via manipulation of incident light.
What is Bragg reflector?
Bragg reflectors are structures of alternating layers of materials with different refractive indices. These structures dominantly reflect at a certain peak wavelength in relation to the individual separation of the layers. Each boundary layer exhibits partial reflection which through superposition lead to interference phenomena. The peak reflected wavelength is 4 times the spacing distance between layers whereby the path difference is such as to allow constructive interference. This is the fundamental principle behind thin film interference, responsible for the rainbow colours reflected by oil droplets on the surface of water and that present on soap films.
What is dynamic iridescence and does work in squid?
(membrane association) Iridescence describes material colour change as the viewing angle or the angle of incidence of light is varied. However dynamic iridescence observed in certain squid genera is believed to be a result of neural control. Specifically, the application of the neurotransmitter Acetyl Choline (ACH) to fresh skin samples resulted in detectable post-translational modifications of the protein, namely phosphorylation. It is believed that phosphorylation of reflectin proteins cause changes in the chemical interactions within the nanoparticles reflectin forms in-vivo within the iridophore. These changes subsequently induce an alteration in the volume of protein platelets of reflectin and critically the thicknesses of reflectin layers in the iridophore. The path difference between incident light on individual layers is thus altered resulting in a shift in peak reflected wavelength and therefore colour.
What is known about the nucleotide sequence of reflectins?
No introns were found in the reflectin genes when reflectin genes amplified from Euprymna scolopes genomic DNA were sequenced. (2)
What is known about the unusual 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?
References
1. Kramer et al. nature materials 533-538 VOL 6 JULY 2007
2. Crookes et al. p235-238 SCIENCE VOL 303 9 JANUARY 2004
The Experiments
Part 3
Results
