7-Aminoactinomycin D (7-AAD) is a

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 ...

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with a strong affinity for DNA. It is used as a fluorescent marker for DNA in

fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. "Fluorescence microscop ...

and

flow cytometry Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flo ...

. It intercalates in double-stranded DNA, with a high affinity for GC-rich regions, making it useful for

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

banding studies.

Applications

With an absorption maximum at 546 nm, 7-AAD is efficiently excited using a 543 nm

helium–neon laser A helium–neon laser or He-Ne laser, is a type of gas laser whose high energetic medium gain medium consists of a mixture of 10:1 ratio of helium and neon at a total pressure of about 1 torr inside of a small electrical discharge. The bes ...

; it can also be excited with somewhat lower efficiency using a 488 nm or 514 nm argon laser lines. Its emission has a very large Stokes shift with a maximum in the deep red: 647 nm. 7-AAD is therefore compatible with most blue and green fluorophores – and even many red fluorophores – in multicolour applications. 7-AAD does not readily pass through intact

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

s; if it is to be used as a stain for imaging DNA fluorescence, the cell membrane must be permeabilized or disrupted. This method can be used in combination with formaldehyde fixation of samples. 7-AAD is also used as a cell viability stain. Cells with compromised membranes will stain with 7-AAD, while live cells with intact cell membranes will remain dark.

Actinomycin D

The related compound actinomycin D is nonfluorescent, but binds DNA in the same way as 7-AAD. Its

absorbance Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...

changes when bound to DNA, and it can be used as a stain in conventional transmission microscopy.

References

Gallery

File:7-AADSpektrum.png, Absorptions

External links

Structure from Invitrogen

{{DEFAULTSORT:Aminoactinomycin D, 7- Fluorescent dyes Cell imaging Staining dyes Cell biology DNA intercalaters