Texas Red
Encyclopedia
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 immunohistochemistry
.
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
tuned to 595-605 nm, or less efficiently a krypton laser 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 conjugate
s via the sulfonyl chloride (SO2Cl) group. In water, the sulfonyl chloride group of unreacted Texas Red molecules hydrolyses
to sulfonate
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
for conjugation.
A protein with the Texas Red chromophore attached can then itself act as a fluorescent labelling agent; an antibody
with a fluorescent marker attached will bind to a specific antigen
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 antigen
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
, acetonitrile
.
Texas Red, attached to a strand of DNA or RNA, can be used as a molecular beacon
for highlighting specific sequences of DNA
. Texas Red can be linked with another fluorophore
. A tandem conjugate of Texas Red with R-phycoerythrin
(PE-Texas Red) is often used.
Fluorophores, like Texas Red, are commonly used in molecular biology
techniques like quantitative RT-PCR and cellular assay
s.
Labeling efficiency of nucleic acids as well as proteins has to be quantified prior to furhter experiments. In most cases the amount of labeled sample is minimal. Therefore, specialized nano-volume photometer offer the possibility to determine the DNA, RNA or protein concentration of a sample as well as incorporation of Texas Red with submicroliter volumes (starting with 0.3 µl). In addition, due to the reduction of the optical pathlength with the NanoPhotometer samples are diluted automatically in comparison to standard cuvette measurements.
Newer rhodamine
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.
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
, used in histology
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
for staining cell specimens, for sorting cells with fluorescent-activated cell sorting machines, in fluorescence microscopy applications, and in immunohistochemistry
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
.
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
Dye laser
A dye laser is a laser which 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. The wide bandwidth makes them particularly suitable for tunable lasers and...
tuned to 595-605 nm, or less efficiently a krypton laser 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 conjugate
Conjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...
s via the sulfonyl chloride (SO2Cl) group. In water, the sulfonyl chloride group of unreacted Texas Red molecules hydrolyses
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
to sulfonate
Sulfonate
A sulfonate is a salt or ester of a sulfonic acid. It contains the functional group R-SO2O-.- Sulfonate salts:Anions with the general formula RSO2O− are called sulfonates. They are the conjugate bases of sulfonic acids with formula RSO2OH. As sulfonic acids tend to be strong acids, the...
and the molecule becomes the very water soluble sulforhodamine 101
Sulforhodamine 101
Sulforhodamine 101 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....
which is easy to wash out selectively. This is one of the advantages of conjugating with Texas Red vs. using a rhodamine-isothiocyanate
Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinolates. These natural isothiocyanates, such as allyl isothiocyanate, are also...
for conjugation.
A protein with the Texas Red chromophore attached can then itself act as a fluorescent labelling agent; an antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
with a fluorescent marker attached will bind to a specific antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
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 antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
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
Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...
, acetonitrile
Acetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
.
Texas Red, attached to a strand of DNA or RNA, can be used as a molecular beacon
Molecular beacon
Molecular beacons are oligonucleotide hybridization probes that can report the presence of specific nucleic acids in homogenous solutions. The terms more often used is molecular beacon probes. Molecular beacons are hairpin shaped molecules with an internally quenched fluorophore whose fluorescence...
for highlighting specific sequences of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. Texas Red can be linked with another fluorophore
Fluorophore
A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength...
. A tandem conjugate of Texas Red with R-phycoerythrin
Phycoerythrin
Phycoerythrin is a red protein from the light-harvesting phycobiliprotein family, present in cyanobacteria, red algae and cryptomonads.Like all phycobiliproteins, phycoerythrin is composed of a protein part, organised in a hexameric structure of alpha and beta chains, covalently binding...
(PE-Texas Red) is often used.
Fluorophores, like Texas Red, are commonly used in molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
techniques like quantitative RT-PCR and cellular assay
Assay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
s.
Labeling efficiency of nucleic acids as well as proteins has to be quantified prior to furhter experiments. In most cases the amount of labeled sample is minimal. Therefore, specialized nano-volume photometer offer the possibility to determine the DNA, RNA or protein concentration of a sample as well as incorporation of Texas Red with submicroliter volumes (starting with 0.3 µl). In addition, due to the reduction of the optical pathlength with the NanoPhotometer samples are diluted automatically in comparison to standard cuvette measurements.
Newer rhodamine
Rhodamine
Rhodamine 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. They are often used as a tracer dye within water to determine the rate and direction of flow and transport...
derivatives, such as Alexa 594
Alexa (fluor)
The Alexa Fluor family of fluorescent dyes is produced by Molecular Probes, a subsidiary of Invitrogen. Alexa Fluor dyes are typically used as cell and tissue labels in fluorescence microscopy and cell biology....
and DyLight 594
DyLight Fluor
The DyLight Fluor family of fluorescent dyes are produced by Dyomics in collaboration with Thermo Fisher Scientific. DyLight dyes are typically used in biotechnology and research applications as biomolecule, cell and tissue labels for fluorescence microscopy, cell biology or molecular...
, 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
Photobleaching
Photobleaching is the photochemical destruction of a fluorophore. In microscopy, photobleaching may complicate the observation of fluorescent molecules, since they will eventually be destroyed by the light exposure necessary to stimulate them into fluorescing...
or higher fluorescence intensity are needed.