Beautiful Bioluminescence: Cool Chemistry (and Amusing Alliteration?). You’ve all seen the What’s Hot photos. Here comes the science.
• What is it? Bioluminescence is light produced by a chemical reaction within a living organism. It requires a chemical, generically called luciferin, and an enzyme catalyst, luciferase. It is different from fluorescence or phosphorescence, which involve the re-emission of absorbed light.
• Where is it? Over 80% of bioluminescence comes from the ocean. There is virtually none in fresh water,for unknown reasons. On land, most bioluminescence comes from fireflies and mushrooms (see images).
• How did it evolve? Based on the number of distinct light-producing chemical mechanisms, it is estimated that bioluminescence evolved independently at least 40 times! This convergent evolution suggests that it is important to organisms, and also it must be relatively easy to make. In fact, there are surprisingly few luciferins, most are acquired in the food chain (as vitamins or chlorophyll) or synthesized from common amino acids. For example, coelenterazine is the light emitter for nine phyla. However, luciferase enzymes are very different proteins across species. More on chemistry: http://www.lifesci.ucsb.edu/~biolum/chem/detail2.html
• Biophysics: Bioluminescence is typically blue light, which is best suited for the optical transparency of sea water. Sometimes, as in infra-red detecting Malacosteid fish, the initial blue light is absorbed and re-emitted as red, which is then used to find prey. Light intensity varies from 6e8 photons to 2e11photons, lasting from a fraction of second to many tens of seconds long.
• Neuroscience: In multicelled animals, luminescence is neurally controlled by neurotransmitters like glutamate or nor-adrenaline. In single celled dinoflagellates, a proton channel was just cloned that links mechanical perturbation to pH changes, as a trigger for bioluminescence.
• Milky Seas: Did you know that bioluminescence has been observed from satellites? Or that Jules Verne described milky seas in his novel Twenty Thousand Leagues Under the Sea? (I’ll let you intrepid plussers find out more).
• Biomedical Science: Bioluminescence is a favorite tool of researchers (including myself)! Firefly luciferin uses ATP to generate light, so it can be used as a highly sensitive and quantitative biosensor for ATP. If the luciferase gene is inserted into tumor cells, then tumor growth and metastasis can be followed in live mice using whole body imaging. Similarly, bioluminescence generated by jellyfish aqueorin requires calcium ions, so many researchers use it to follow calcium signaling in cells.
#bioluminescence , #sciencesunday for ScienceSunday . Thanks to Allison Sekuler and Robby Bowles for maintaining this Page and inviting me to guest-curate this morning. It was fun!