Rhodamine is a family of related dyes, a subset of the

triarylmethane dye Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes. Families Triarylmethane dyes can be grouped into families accordin ...

s. They are derivatives of

xanthene Xanthene (9''H''-xanthene, 10''H''-9-oxaanthracene) is the organic compound with the formula CH2 6H4sub>2O. It is a yellow solid that is soluble in common organic solvents. Xanthene itself is an obscure compound, but many of its derivatives are us ...

. Important members of the rhodamine family are

Rhodamine 6G Rhodamine 6G is a highly fluorescent rhodamine family dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with ...

Rhodamine 123 Rhodamine 123 is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with instrument ...

, and

Rhodamine B Rhodamine B is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers. ...

. They are mainly used to dye paper and inks, but they lack the

lightfastness Lightfastness is a property of a colourant such as dye or pigment that describes its resistance to fading when exposed to light. Dyes and pigments are used for example for dyeing of fabrics, plastics or other materials and manufacturing paints or ...

for fabric dyeing.

Use

Aside from their major applications, they are often used as a

tracer dye Dye tracing is a method of tracking and tracing various Fluid dynamics, flows using dye as a flow tracer when added to a liquid. Dye tracing may be used to analyse the flow of the liquid or the transport of objects within the liquid. Dye tracking m ...

, e.g. to determine the rate and direction of flow and transport of water. Rhodamine dyes

fluoresce 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 ...

and can thus be detected easily and inexpensively with instruments called

fluorometer A fluorometer, fluorimeter or fluormeter is a device used to measure parameters of visible spectrum fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters ar ...

s. Rhodamine dyes are used extensively in biotechnology applications such as

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 ...

, flow cytometry,

fluorescence correlation spectroscopy Fluorescence correlation spectroscopy (FCS) is a statistical analysis, via time correlation, of stationary fluctuations of the fluorescence intensity. Its theoretical underpinning originated from L. Onsager's regression hypothesis. The analysis p ...

and

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...

. Rhodamine 123 is used in biochemistry to inhibit mitochondrion function. Rhodamine 123 appears to bind to the mitochondrial membranes and inhibit transport processes, especially the electron transport chain, thus slowing down

cellular respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...

. It is a substrate of P-glycoprotein (Pgp), which is usually overexpressed in cancer cells. Recent reports indicate that rhodamine 123 may also be a substrate of multidrug resistance-associated protein (MRP), or more specifically,

MRP1 Multidrug resistance-associated protein 1 (MRP1) is a protein that in humans is encoded by the ''ABCC1'' gene. Function The protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins t ...

. In addition to their major applications, rhodamines are used in

dye laser A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 ...

gain media The active laser medium (also called gain medium or lasing medium) is the source of optical gain (laser), gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy ...

Other derivatives

There are many rhodamine derivatives used for imaging purposes, for example Carboxytetramethylrhodamine (TAMRA), tetramethylrhodamine (TMR) and its isothiocyanate derivative (TRITC) and,

sulforhodamine 101 Sulforhodamine 101 (SR101) is a red fluorescent dye. In neurophysiological experiments which comprise calcium imaging methods, it can be used for a counterstaining of astrocytes to be able to analyze data from neurons separately. However, in ad ...

(and its sulfonyl chloride form

Texas Red Texas Red or sulforhodamine 101 acid chloride is a red fluorescent dye, used in histology for staining cell specimens, for sorting cells with fluorescent-activated cell sorting machines, in fluorescence microscopy applications, and in immunohis ...

) and Rhodamine Red. TRITC is the base rhodamine molecule functionalized with an

isothiocyanate In organic chemistry, isothiocyanate is the functional group , formed by substituting the oxygen in the isocyanate group with a sulfur. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosi ...

group (−N=C=S), replacing a

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

atom on the bottom ring of the structure. This derivative is reactive towards

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

groups on proteins inside cells. A succinimidyl-ester functional group attached to the rhodamine core, creating NHS-rhodamine, forms another common amine-reactive derivative. Other derivatives of rhodamine include newer fluorophores such as Alexa 546, Alexa 633, DyLight 550 and DyLight 633, HiLyte fluor 555 HiLyte 594, Janelia Dyes JF549 and JF669 have been tailored for various chemical and biological applications where higher

photostability Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...

, increased brightness, different spectral characteristics, or different attachment groups are needed. Substituents of the

core are influencing the properties of the

dyes by both electrocnic and steric effects. Specifically designed

substituents A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...

also allows to allow xanthenes to bear specific funtions activatable upon excitation by

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

, e.g. they could act as photoremovable protecting group for

carboxylates In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...

and

halides In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

(thus being a photo

CORM A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ' ...

), or added as a secondary functionality of fluorescent dyes, e.g. fluorescent

pH indicators A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH ( acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Henc ...

References

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External links

Absorption and Emission Spectra of Rhodamine B
*Berlier et al. 2003 J. Histochem Cytochem refers to Alexa 633 as a rhodamine derivative. * Staining dyes Laser gain media Fluorescent dyes