Firefly luciferin
Firefly luciferin is the light‑emitting molecule used by fireflies and several related glow-worm beetles. It is the substrate that the enzyme luciferase acts on to produce light. When oxygen is present and the cell provides ATP and magnesium, luciferin is oxidized, goes through a high‑energy intermediate, and releases energy as visible light. The typical glow is in the green‑yellow to orange range (roughly 530–630 nm), but the color can vary among species and conditions.
Historically, luciferin was first isolated and purified in 1949 by William D. McElroy’s group at Johns Hopkins University. Emil H. White later crystallized and fully characterized the compound. In early work, luciferin was extracted from thousands of firefly lanterns using acid–base chemistry and organic solvents. In solution, luciferin absorbs ultraviolet light around 327 nm and emits light around 530 nm; changes in pH can shift some properties, but the emission color is mainly determined by the luciferase enzyme and the environment.
The chemical formula is C11H8N2O3S2, and solid luciferin appears as a yellow powder. The final step of its natural assembly is believed to be a condensation between D‑cysteine and 2‑cyano‑6‑hydroxybenzothiazole. In fireflies, oxidation of luciferin by luciferase yields a high‑energy peroxide that decomposes to produce light.
Luciferin and its variants are widely used in bioluminescence imaging and research. Modifications of the molecule can shift the emission toward red, with some derivatives emitting up to about 675 nm. Beyond imaging, luciferin serves as a fatty‑acid–mimicking substrate in studies of metabolism and is used in assays related to the ABCG2 transporter and fatty‑acid–related enzymes.
This page was last edited on 2 February 2026, at 13:06 (CET).