Digoxigenin is a steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...

 found exclusively in the flowers and leaves of the plants Digitalis purpurea
Digitalis purpurea
Digitalis purpurea , is a flowering plant in the family Plantaginaceae , native to most of Europe.-Description:...

, Digitalis orientalis and Digitalis lanata
Digitalis lanata
Digitalis lanata is a species of foxglove that is part of the Plantaginaceae family. It gets its name due to the texture of the leaves. Digitalis lanata, like some other foxglove species, is highly toxic in all parts of the plant...

(foxgloves), where it is attached to sugars, to form the glycosides
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...

 (eg. Lanatoside C
Lanatoside C
Lanatoside C is a cardiac glycoside, which can be used by the intravenous route. It is marketed as Cedilanide in Brazil by Novartis. Its main indications are rapid responde atrial fibrilation and paroxistic supraventricular tachycardia. Its structure is composed of 4 sugars and an aglycon named...


Use in biotechnology

Digoxigenin is considered a hapten
A hapten is a small molecule that can elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself...

, a small molecule with high immunogenicity used in many molecular biology applications. Other popular haptens include DNP (dinitrophenol
2,4-Dinitrophenol , C6H4N2O5, is a cellular metabolic poison. It uncouples oxidative phosphorylation by carrying protons across the mitochondrial membrane, leading to a rapid consumption of energy without generation of ATP....

), biotin
Biotin, also known as Vitamin H or Coenzyme R, is a water-soluble B-complex vitamin discovered by Bateman in 1916. It is composed of a ureido ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring...

, and fluorescein
Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....

. In general, antibodies
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...

 generated against haptens have higher affinities for their targets than other antibodies, so haptens are conjugated
Bioconjugation is the process of coupling two biomolecules together in a covalent linkage. Common types of bioconjugation chemistry are amine coupling of lysine amino acid residues , sulfhydryl coupling of cysteine residues , and photochemically initiated free radical reactions, which have broader...

 to other biological molecules as all-purpose immuno-tags. This is because anti-hapten antibodies have high affinities and are readily available, while antibodies may not be commercially available for exotic biological targets.

Digoxigenin is a standard immunohistochemical
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...

 marker for in situ hybridization. In this case it is conjugated to a single species of RNA nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...

 triphosphate (typically uridine
Uridine is a molecule that is formed when uracil is attached to a ribose ring via a β-N1-glycosidic bond.If uracil is attached to a deoxyribose ring, it is known as a deoxyuridine....

), which is then incorporated into RNA (a "riboprobe
Riboprobes are RNA probes that can be produced by in vitro transcription of cloned DNA inserted in a suitable plasmid downstream of a viral promoter. Some bacterial viruses code for their own RNA polymerases, which are highly specific for the viral promoters...

") as it is synthesized by the cellular machinery. Later, the digoxigenin ("Dig") markers are detected with anti-digoxigenin antibodies, which may be labeled with dyes or enzymes (see ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...

) for visualization and detection. In a similar manner, digoxigenin may be conjugated to sugars
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...

 to study glycosylation
Glycosylation is the reaction in which a carbohydrate, i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule . In biology glycosylation refers to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules...

events in biological systems.
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