Methyl green (CI 42585) is a

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

ic or positive charged

stain A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials app ...

related to Ethyl Green that has been used for staining

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

since the 19th century. It has been used for staining

cell nuclei The cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoc ...

either as a part of the classical Unna-Pappenheim stain or as a nuclear

counterstain A counterstain is a stain with colour contrasting to the principal stain, making the stained structure easily visible using a microscope. Examples include the malachite green counterstain to the fuchsine stain in the Gimenez staining techniqu ...

ever since.
In recent years, its

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

properties, when bound to DNA, have positioned it as useful for

far-red Far-red light is a range of light at the extreme red end of the visible spectrum, just before infrared light. Usually regarded as the region between 700 and 750 nm wavelength, it is dimly visible to human eyes. It is largely reflected or transmit ...

imaging of live cell nuclei. Fluorescent DNA staining is routinely used in cancer prognosis. Methyl green also emerges as an alternative stain for DNA in

agarose Agarose is a heteropolysaccharide, generally extracted from certain red algae. It is a linear polymer made up of the repeating unit of agarobiose, which is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose. Agarose is on ...

gels,

fluorometric assays Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition. Enzyme units The quantity or concentration of an enzyme can be expressed in molar amounts, as with any ...

, and

flow cytometry Flow cytometry (FC) is a technique used to detect and measure the 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 ...

. It has also been shown that it can be used as an exclusion

viability Viability or viable may refer to: Biology, medicine or ecology * Viability selection, the selection of individual organisms who can survive until they are able to reproduce * Fetal viability, the ability of a fetus to survive outside of the uter ...

stain for cells. Its interaction with DNA has been shown to be non-intercalating, in other words, not inserting itself into the DNA, but instead

electrostatic Electrostatics is a branch of physics that studies slow-moving or stationary electric charges. Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word (), mean ...

with the DNA

major groove In molecular biology, the term double helix refers to the structure formed by double-stranded molecules of nucleic acids such as DNA. The double helical structure of a nucleic acid complex arises as a consequence of its secondary structure, a ...

. It is used in combination with pyronin in the methyl green–pyronin stain, which stains and differentiates DNA and RNA. When excited at 244 or 388 nm in a neutral aqueous solution, methyl green produces a fluorescent emission at 488 or 633 nm, respectively. The presence or absence of DNA does not affect these fluorescence behaviors. When binding DNA under neutral aqueous conditions, methyl green also becomes fluorescent in the far red with an excitation maximum of 633 nm and an emission maximum of 677 nm. Commercial Methyl green preparations are often contaminated with

Crystal violet Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triphenylmethane, triarylmethane dye used as a histological stain and in Gram staining, Gram's method of classifying bacteria. Crystal ...

. Crystal violet can be removed by

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

extraction.

References

{{reflist Biological techniques and tools Staining dyes Triarylmethane dyes Dimethylamino compounds Chlorides