Fura-2, an
aminopolycarboxylic acid left, 120px, a metal complex with the EDTA anion
120px, Aspartic acid is an aminodicarboxylic acid and precursor to other ligands.
An aminopolycarboxylic acid (sometimes abbreviated APCA) is a chemical compound containing one or more nitrogen at ...
, is a ratiometric
fluorescent
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
dye which binds to free intracellular
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...
. It was the first widely used dye for
calcium imaging, and remains very popular. Fura-2 is excited at 340
nm and 380 nm of light, and the ratio of the emissions at those wavelengths is directly related to the amount of intracellular calcium. Regardless of the presence of calcium, Fura-2 emits at 510 nm of light. The use of the ratio automatically cancels out confounding variables, such as variable dye concentration and cell thickness, making Fura-2 one of the most appreciated tools to quantify calcium levels. The high photon yield of fura-2 allowed the first real time (video rate) measurements of calcium inside living cells in 1986. More recently, genetically-encoded calcium indicators based on spectral variants of the
green fluorescent protein
The green fluorescent protein (GFP) is a protein that exhibits bright green fluorescence when exposed to light in the blue to ultraviolet range. The label ''GFP'' traditionally refers to the protein first isolated from the jellyfish '' Aequor ...
, such as
Cameleons,
have supplemented the use of Fura-2 and other small molecule dyes for calcium imaging, but Fura-2 remains faster.
See also
*
Fura-2AM, a membrane-permeant derivative of Fura-2
*
Indo-1
References
{{reflist
Biochemistry methods
Cell culture reagents
Cell imaging
Chelating agents
Fluorescent dyes
Oxazoles
Benzofuran ethers at the benzene ring
Potassium compounds
Hydroquinone ethers
Glycol ethers
Anilines