What Makes Fireflies Glow?

Pretty soon, when you look outside at night you will notice the intermittent glow of fireflies throughout your backyard. This is one of the sure-tell signs that summer is finally here and while these twinkling bugs can keep us in awe for what seems like hours at a time, there is some serious chemistry happening in their bodies.

Research shows that fireflies glow when a substrate called luciferin – an enzyme called luciferase and oxygen – combine to produce a chemical reaction that causes their abdomens to light up. But Dr. Bruce Branchini, a chemist from Connecticut College, proved that’s only part of the story when he replicated the reaction in the lab.

Dr. Branchini and his colleagues discovered that it also takes a charged particle to create the magical glow fireflies give off called superoxide. Dr. Branchini used a special instrument that uses a magnet and microwaves that were able to trap the reaction long enough to see what was happening. If the superoxide was present, it would react with another substance in such a way as to confirm its presence.

Dr. Branchini’s findings could hopefully lead to new biomedical procedures such as improving the detection of cancerous cells by using bioluminescence methods. Instead of using an MRI or taking tissue samples to monitor a tumor, doctors could make it more visible by lighting it up, a procedure that would be much less invasive.


Classroom Discussion

  • What other living organisms glow? Why do they glow?
  • What other applications are there for bioluminescence?


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