Texas Red or sulforhodamine 101 acid chloride is a red

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 ...

dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...

, used in

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

for

staining Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissue (biology), tissues), in cytology (microscopic ...

cell specimens, for sorting cells with fluorescent-activated cell sorting machines, 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. A fluorescence micro ...

applications, and in

immunohistochemistry Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of Antibody, antibodies binding specifically to antigens in biological tissues. Alber ...

. Texas Red fluoresces at about 615 nm, and the peak of its absorption spectrum is at 589 nm. The powder is dark purple. Solutions can be excited by a

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 n ...

tuned to 595-605 nm, or less efficiently a

krypton laser An ion laser is a gas laser that uses an ionized gas as its lasing medium. Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry–Pérot resonator. Unlike helium–neon lasers, the ...

at 567 nm. The absorption extinction coefficient at 596 nm is about 85,000 M⁻¹cm⁻¹. The compound is usually a mixture of two monosulfonyl chlorides, i.e., as pictured, or with the SO₃ and SO₂Cl groups exchanged. It can be used as a marker of proteins, with which it easily forms conjugates via the

sulfonyl chloride In chemistry, a sulfonyl halide consists of a sulfonyl () group singly bonded to a halogen atom. They have the general formula , where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > ...

(SO₂Cl) group. In water, the

group of unreacted Texas Red molecules

hydrolyses Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

sulfonate In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the conjugate bases of ...

and the molecule becomes the very water-soluble sulforhodamine 101 which is easy to wash out selectively. This is one of the advantages of conjugating with Texas Red vs. using a rhodamine-

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 ...

for conjugation. A protein with the Texas Red chromophore attached can then itself act as a fluorescent labeling agent; an

antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

with a fluorescent marker attached will bind to a specific

antigen In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

and then show the location of the antigens as shining spots when irradiated. It is relatively bright, and therefore can be used to detect even weakly expressed

s. Other molecules can be labeled by Texas Red as well, e.g., various toxins. The dye dissolves very well in water as well as other polar solvents, e.g.,

Dimethylformamide Dimethylformamide, DMF is an organic compound with the chemical formula . Its structure is . Commonly abbreviated as DMF (although this initialism is sometimes used for 2,5-dimethylfuran, dimethylfuran, or dimethyl fumarate), this colourless liqui ...

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

. Texas Red, attached to a strand of DNA or RNA, can be used in Fluorescent ''in situ'' Hybridisation (FISH) as a

molecular beacon Molecular beacons, or molecular beacon probes, are oligonucleotide hybridization probes that can report the presence of specific nucleic acids in homogenous solutions. Molecular beacons are Stem-loop, hairpin-shaped molecules with an internally Que ...

for highlighting specific sequences of

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 ...

. Texas Red can be linked with another

fluorophore A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with se ...

. A tandem conjugate of Texas Red with R-

phycoerythrin Phycoerythrin (PE) is a red protein-pigment complex from the light-harvesting phycobiliprotein family, present in cyanobacteria, red algae and Cryptomonad, cryptophytes, accessory to the main chlorophyll pigments responsible for photosynthesis.The ...

(PE-Texas Red) is often used. Fluorophores, like Texas Red, are commonly used in

molecular biology Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...

techniques like quantitative

RT-PCR Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase chain ...

and cellular

assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity ...

s. Newer

rhodamine Rhodamine is a family of related dyes, a subset of the triarylmethane dyes. They are derivatives of xanthene. Important members of the rhodamine family are rhodamine 6G, Rhodamin WT, Texas Red (Sulforhodamin 101), rhodamine 123, and rhod ...

derivatives, such as Alexa 594 and DyLight 594, have been tailored to match the excitation and emission spectra of Texas Red and are used in various chemical and biological applications where greater photostability or higher fluorescence intensity are needed.

References

{{reflist Staining dyes Rhodamine dyes Triarylmethane dyes Nitrogen heterocycles Oxygen heterocycles Heterocyclic compounds with 7 or more rings