Team:Cambridge/Project

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OVERVIEW
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Bactiridescence was based around the properties of <a href='/Team:Cambridge/Reflectin'>reflectin</a>, a squid protein with the highest refractive index of any known proteinaceous substance. In squid this protein forms complex platelets which act as Bragg reflectors to provide camouflage.

We aimed to <a href='/Team:Cambridge/Project/In_Vivo'>express reflectin in E. Coli</a> and to investigate it's optical properties in order to build the groundwork for the manipulation of living structural colour. We also looked at the <a href='/Team:Cambridge/Project/In_Vitro'>over-expression of reflectin in E.Coli</a>, in order to obtain relatively pure samples of the protein for making thin films.

Initially we looked at some squid tissue using a confocal microscope, to see it's effect in squid cells.

When we over-expressed reflectin in E.Coli, we found (by making a GFP fusion) that while reflectin is surprisingly non-toxic to E.Coli, it formed inclusion bodies. We then extracted these inclusion bodies, purified the protein using a number of different techniques, and made thin films by spin-coating.

In order to express reflectin at lower levels, we made an arabinose inducible version, both with and without a GFP-fusion. We found that at lower levels of expression, reflectin would not form inclusion bodies, but appeared to be uniformly distributed throughout the cell. We made several attempts to image this – hoping to find some change in optical properties – but found that while the induced cells did appear to exhibit iridescence, so did the uninduced. This, we theorise, is due to thin film interference around the cell wall and membrane.

We also attempted to export both our reflectin and our reflectin-GFP to the periplasm, in the hope that this environment would be more similar to the environment in which reflectin naturally occurs. As of writing, this has yet to be successful .

Our project attempts to lay some groundwork for future research in to reflectins. Reflectin has several possible future applications, from display technologies to rapid bio-reporters.