Glow in the Dark

One of Cate’s top ten good things about living in Indiana is the fireflies. While I am not a biologist and know very little about the critter itself, I am well versed in the reaction that occurs to produce the glowing abodomen and it's biomedical applications. In response to my comment, Cate has invited me to teach her chemistry (and by extension anyone else who stops by here). I am never one to turn down an opportunity to teach, so here goes.

Bioluminescence (from the Greek bios meaning living and Latin lumen meaning light) is the production and emission of light by a living organism as the result of a chemical reaction in which chemical energy is converted to light energy. For a firefly the reaction is the oxidation of luciferin. The basic component sof the reaction are as follows:

Oxygen (O2) + Luciferin --> Oxyluciferin + Energy (Light)

This reaction occurs very slowly independently, but in the presence of luciferase (an enzyme) the reaction rate increases.

Luciferase can be used as a reporter system for biomedical imaging research. Cells can have DNA added to them that includes the luciferase gene linked to a gene of interest. When the gene of interest is expressed by the cells, so is the luciferase. When the substrate, luciferin, is added, if luciferase is being expressed, the luciferin will be oxidized and the cells will glow. If luciferase, and hence the gene of interest, are not being expressed, then any bioluminescence will be minimal to non-existent. Thus, the luciferase reports on the activation status of one’s gene of interest.
This image overlays a bioluminescent image over a photo of a mouse who has been implanted with breast cancer cells labeled with a luciferese reporter gene. Serial bioluminescent imaging of a tumor such as this one will allow the researchers to monitor tumor growth, or possibly metastasis, non-invasively. While such a method would not be possible for human patients, it is helpful in the drug design and testing.

Any questions?