What Is Coelenterazine?

1. What Is Coelenterazine?

· Chemical nature: Coelenterazine (also known as Renilla luciferin) is an imidazo[1,2-a]pyrazin-3-one derivative, often orange-yellow crystalline solid with peak UV absorption around 435 nm.

· It serves as a luciferin, meaning it is oxidized in luciferase-or photoprotein-catalyzed reactions to emit light (bioluminescence).

2. Origins & Natural Sources

· Discovered independently in the sea pansy Renilla reniformis and jellyfish Aequorea victoria, named after phylum Coelenterata.

· Interestingly, jellyfish do not synthesize it—they obtain it from their diet (e.g. crustaceans, copepods).

· Naturally present in many marine organisms: radiolarians, ctenophores, cnidarians, copepods, shrimp, squid, fish and even non-luminescent species like Atlantic herring.

· Biochemically, biosynthesis in species like Metridia longa starts from tyrosine and phenylalanine via a cyclized FYY peptide.

3. Applications—Where It’s Used

· Calcium sensing via photoproteins (e.g. aequorin, obelin): upon Ca²⁺ binding, coelenterazine oxidation emits blue light (~465 nm) measured to monitor intracellular calcium flux in living cells and organisms.

· Luciferase reporter systems: used with Renilla luciferase (Rluc), Gaussia luciferase (Gluc), Metridia luciferase for reporter gene assays, BRET-based proteinprotein interaction studies, and HTS/ELISA-type assays

· Reactive oxygen species detection: as a chemiluminescent probe, it reacts with superoxide anion and peroxynitrite—used in assays detecting oxidative stress, tumor microenvironment ROS, etc.

4. How to Use Coelenterazine—Practical Details

· Solubility & handling: poorly soluble in water. Typically prepared fresh in 100% ethanol, DMSO or methanol. Avoid buffers alone, as precipitation can occur—and IV injection of precipitate may be toxic to animals.

· Prepare working stocks immediately before use (it is unstable in solution), store aliquots at −20 °C under inert gas/dark conditions.

· For cellular experiments involving live cells expressing apoaequorin, add coelenterazine to culture medium to reconstitute functional photoprotein inside cells.

· Concentration varies based on assay type—typically low micromolar (e.g. 2–8 µM for reporter/BRET assays).

5. Advantages & Usage Tips

· High sensitivity & minimal background: bioluminescence does not require external excitation light, eliminating autofluorescence and phototoxicity.

· Low leakage and no compartmentalization compared to fluorescent dyes, since aequorin is a large protein and remains intracellular.

· Derivatives such as Coelenterazine-h offer 10–20× higher luminescent intensity than native CTZ—ideal for detecting subtle Ca²⁺ changes.

· Limitations: The luciferin is consumed irreversibly, so continuous addition may be needed for time-course or repeated measurements. It is sensitive to oxygen and light, so handle rapidly and protected from air / light exposure.

6. Radical Thinking & Innovations

· Novel CTZ derivatives engineered with red-shifted emission or longer half-lives could enable deeper tissue imaging in vivo (NIR-emitting analogs).

· Multiplexed biosensors: combining CTZ-based BRET systems with fluorescent protein sensors for multi-signal imaging in single cells.

· Real-time in vivo oxidative stress imaging: leveraging CTZ chemiluminescence in live animal models of inflammation or cancer to non-invasively map ROS dynamics.

· Cell-penetrant CTZ pro-substrates: novel masked forms that are activated intracellularly to improve targeting and reduce background.

7. Coelenterazine from Aladdin Scientific

· Aladdin (Shanghai, also US-based Aladdin Scientific) offers product code C131248 Coelenterazine (native, ≥94% purity) with recommended storage at −20 °C, protected from light and argon-charged conditions Aladdin Scientific.

· Their product information is consistent with global standards for research-grade reagents: typically supplied as 10 mM in DMSO solution (product code C580349 )or solid form, suitable for molecular and cell biology applications.

Summary Table

Topic	Key Points
What	CTZ is a marine luciferin, oxidized by luciferases to emit light.
Where from	Found in marine organisms; acquired via diet; biosynthesis in some copepods.
Applications	Ca²⁺ sensors (aequorin), BRET reporter assays, ROS detection, bioluminescent imaging.
Usage	Dissolve fresh in ethanol/DMSO, store cold/dark, prepare fresh, use low µM concentrations.
Advantages	High sensitivity, low background, no excitation needed, stable intracellular reporter.
Tips	Use Coelenterazine-h for stronger signal; prevent precipitation; handle carefully for live-cell or in vivo use.

Final Thoughts

Coelenterazine remains a gold-standard reagent in bioluminescence research—with powerful applications in molecular biology, imaging, biosensing, and high-throughput screening. Choosing the right derivative (e.g. CTZ-h), careful handling (fresh solutions, protection from light/oxygen), and creative assay designs (e.g. multiplexed BRET or ROS imaging) can make it even more versatile in cutting-edge research.

Aladdinsci: https://www.aladdinsci.com