Rhodamine is a family of related dyes, a subset of the triarylmethane dyes. 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 u ...

. Important members of the rhodamine family are rhodamine 6G, Rhodamin WT, Texas Red (Sulforhodamin 101), rhodamine 123, and rhodamine B. They are mainly used to dye paper and inks, but they lack the lightfastness for fabric dyeing.

Use

Aside from their major applications, they are often used as a tracer dye, e.g. to determine the rate and direction of flow and transport of water. Rhodamine dyes

fluoresce 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 ...

and can thus be detected using Fluorometers. 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. A fluorescence micro ...

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 ...

, fluorescence correlation spectroscopy 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 is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of ...

. Rhodamine 123 is used in biochemistry to inhibit

mitochondrion A mitochondrion () is an organelle found in the cell (biology), cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosine tri ...

function. Rhodamine 123 appears to bind to the mitochondrial membranes and inhibit transport processes, especially the

electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...

, thus slowing down

cellular respiration Cellular respiration is the process of oxidizing biological fuels using an inorganic electron acceptor, such as oxygen, to drive production of adenosine triphosphate (ATP), which stores chemical energy in a biologically accessible form. Cell ...

. It is a substrate of

P-glycoprotein P-glycoprotein 1 (permeability glycoprotein, abbreviated as P-gp or Pgp) also known as multidrug resistance protein 1 (MDR1) or ATP-binding cassette sub-family B member 1 (ABCB1) or cluster of differentiation 243 (CD243) is an important protein ...

(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. In addition to their major applications, rhodamines are used in dye laser as gain media.

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 (and its sulfonyl chloride form Texas Red) and Rhodamine Red. TRITC is the base rhodamine molecule functionalized with an

isothiocyanate In organic chemistry, isothiocyanate is a functional group as found in compounds with the formula . Isothiocyanates are the more common isomers of thiocyanates, which have the formula . Occurrence Many isothiocyanates from plants are produce ...

group (−N=C=S), replacing a

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

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

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

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

core are influencing the properties of the

dyes by both electronic and steric effects. Specifically designed

substituents In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety (chemistry), moiety in the resultant (new) molecule. The suffix ''-yl'' is used when naming organic compounds that conta ...

also allows xanthenes to bear specific functions activatable upon excitation by

visible light Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...

, e.g. they could act as

photoremovable protecting group A photolabile protecting group (PPG; also known as: photoremovable, photosensitive, or photocleavable protecting group) is a chemical modification to a molecule that can be removed with light. PPGs enable high degrees of chemoselectivity as they al ...

for carboxylates 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 fluo ...

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

(thus being a photo

CORM 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 ''c ...

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

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