Rhodamine

    Rhodamine (IPA: /ˈroʊdəmiːn/) is a family of related chemical compounds, fluorone dyes. Examples are Rhodamine 6G and Rhodamine B. They are used as a dye and as a dye laser gain medium. 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 instruments called fluorimeters. Rhodamine dyes are used extensively in biotechnology applications such as fluorescence microscopy, flow cytometry and ELISA.

Rhodamine dyes are generally toxic, and are soluble in water, methanol and ethanol.

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Rhodamine B

Molecular Formula: C₂₈H₃₁N₂O₃Cl

Molecular Weight: 479.02 grams per mole

CAS Number: 81-88-9

SMILES structure: [Cl-].CCN(CC)c1ccc2c(OC3=CC(C=CC3=C2c4ccccc4C(O)=O)=[N+](CC)CC)c1

Rhodamine B is used in biology as a staining fluorescent dye, sometimes in combination with auramine O, as the auramine-rhodamine stain to demonstrate acid-fast organisms, notably Mycobacterium.

Rhodamine B is tunable around 610 nm when used as a laser dye.

Rhodamine B is also called Rhodamine 610, Basic Violet 10, or C.I. 45170.

Rhodamine 6G

  Molecular Formula: C₂₈H₃₁N₂O₃Cl

Molecular Weight: 479.02 g/mol

CAS Number: 989-38-8

SMILES structure: [Cl-].CCNc1cc2OC3=CC(=[NH+]CC)C(=CC3=C(c2cc1C)c4ccccc4C(=O)OCC)C

Rhodamine 6G is often used as a laser dye, and is pumped by the 2nd (532 nm) harmonic from a Nd:YAG laser. The dye has a remarkably high photostability, high quantum yield, low cost, and its lasing range has close proximity to its absorption maximum (approximately 530 nm). The lasing range of the dye is 555 to 585 nm with a maximum at 566 nm.

Rhodamine 6G is also called Rhodamine 590, R6G, Basic Rhodamine Yellow , or C.I. 45160.

Rhodamine 123

The laser dye rhodamine 123 is also used in biochemistry to inhibit mitochondrion function. Rhodamine 123 seems to bind to the mitochondrion membranes and inhibit transport processes, especially the electron transport chain, thus slowing down inner respiration. It is a substrate of P-glycoprotein (Pgp), which is usually overexpressed in cancer cells. Recent reports indicate that rhodamine 123 may be also a substrate of multidrug resistance-associated protein (MRP), or more specifically, MRP1.

Other Rhodamine Derivatives

There are many rhodamine derivatives used for imaging purposes, for example the tetramethyl rhodamine derivatives TRITC and TAMRA, sulforhodamine 101 (and its sulfonyl chloride form Texas Red) and Rhodamine Red. TRITC is the base rhodamine molecule functionalized with an isothiocyanate group (-N=C=S), replacing a hydrogen atom on the bottom ring of the structure. This derivative is reactive towards amine 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 555, Alexa 633, DyLight 549 and DyLight 633, have been tailored for various chemical and biological applications where higher photostability, increased brightness, different spectral characteristics, or different attachment groups are needed.