Glowing insights: luciferase in research

Bioluminescence and chemiluminescence both occur as the result of an enzymatic reaction. Chemiluminescence is the emission of light, due to chemical reactions. For example found in glow sticks. When chemiluminescence takes place in living organisms such as insects, the phenomenon is called bioluminescence. Therefore, bioluminescence is one particular form of chemiluminescence. However, bioluminescence is emitted by a biological source, while chemiluminescence occurs as the result of a non-biological chemical reaction. A well-known bioluminescence example is the reaction of luciferin with ATP in the presence of the enzyme luciferase, which occurs within fireflies to produce their light.⁽¹⁾

Photoluminescence is distinct from bioluminescence and chemiluminescence in that it requires the excitation energy to come from a light source. Photoluminescence light emission is caused by the absorption of photons. Following the absorption of light with a specific wavelength, specialized molecules known as fluorophores produce emissions at another, longer wavelength to return to their ground state. There are two main types Fluorescence and Phosphorescence. Fluorescence occurs when a substance absorbs photons and re-emits them very quickly, within nanoseconds. An everyday example is a fluorescent highlighter pen, which glows under UV light. Phosphorescence is similar to fluorescence, but the substance re-emits the absorbed photons over a longer period, resulting in a sustained glow even after the removal of the exciting source. Glow-in-the-dark stars are a common example. ⁽²⁾

Luciferase enzymes have been isolated from many different species. These include the North American firefly (Photinus pyralis), the sea pansy (Renilla reniformis), and the Jamaican click beetle (Pyrophorus plagiophthalamus), as well as various bacteria, glow-worms, and fish. Reasons that these organisms produce bioluminescence include to attract a mate, lure in prey, and scare away predators. Bioluminescence may also serve as a form of counterillumination camouflage.

Depending on the species in question, the spectral properties of the emitted light can vary considerably. For example, the North American firefly produces yellow-green emissions, and the sea pansy emits blue light, while the Jamaican click beetle expresses several distinct luciferases that are each capable of emitting light of a different color. This spectral diversity can be exploited for multiplexed applications, provided the chosen luciferases have distinct substrate specificities.