What is the difference between fluorescence and bioluminescence?
Fluorescence occurs when a molecule absorbs light from an outside source and then emits light due to the excitation and relaxation of electrons within the molecule, respectively. An example of a fluorescent compound is green fluorescent protein (GFP). Bioluminescence describes light creation by living organisms via chemical reactions between molecules without requiring the absorption of light from an outside source. For example, enzymes called luciferases act on pigment molecules called luciferins to create bioluminescence in insects such as fireflies, marine organisms, and some fungi and bacteria. Fluorescent and bioluminescent molecular compounds are commonly used in conjunction with optical imaging in preclinical research studies.