Digoxigenin (DIG) is a

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...

found exclusively in the flowers and leaves of the plants '' Digitalis purpurea'', '' Digitalis orientalis'' and '' Digitalis lanata'' (foxgloves), where it is attached to sugars, to form the

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

s (e.g. Lanatoside C).

Use in biotechnology

Digoxigenin is a

hapten In immunology, haptens are small molecules that 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 (in general, only large molecules, i ...

, a small

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and b ...

with high antigenicity, that is used in many molecular biology applications similarly to other popular haptens such as

2,4-Dinitrophenol 2,4-Dinitrophenol (2,4-DNP or simply DNP) is an organic compound with the formula HOC6H3(NO2)2. It is a yellow, crystalline solid that has a sweet, musty odor. It sublimates, is volatile with steam, and is soluble in most organic solvents as well ...

biotin Biotin (or vitamin B7) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name ''biotin'', bo ...

, and

fluorescein Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used ...

. Typically, digoxigenin is introduced chemically (

conjugation Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change ...

) into biomolecules (proteins, nucleic acids) to be detected in further assays. K_d of the digoxigenin-antibody interaction has been estimated at ~12 nM (compare to K_d~0.1pM for the biotin-streptavidin interaction). DIG-binding proteins. Tinberg et al. designed artificial proteins that bind DIG. Their best binder, DIG10.3, was a 141 amino acid protein that bound DIG with a

dissociation constant In chemistry, biochemistry, and pharmacology, a dissociation constant (K_D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex ...

(K_d) of 541 (+/- 193) pM. Anti-digoxigenin

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of ...

with high

affinities In post-classical history, an affinity was a collective name for the group (retinue) of (usually) men whom a lord gathered around himself in his service; it has been described by one modern historian as "the servants, retainers, and other fol ...

and specificity are used in a variety of biological immuno-assays (e.g.

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 uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...

). The antibodies are labeled with dyes, enzymes or fluorescence, directly or secondarily, for visualization and detection. Digoxigenin is thus an all-purpose immuno-tag, and in particular a standard immunohistochemical marker for

in situ hybridization ''In situ'' hybridization (ISH) is a type of hybridization that uses a labeled complementary DNA, RNA or modified nucleic acids strand (i.e., probe) to localize a specific DNA or RNA sequence in a portion or section of tissue (''in situ'') or ...

. In this case it is conjugated to a single species of RNA

nucleoside Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleoti ...

triphosphate (typically

uridine Uridine (symbol U or Urd) is a glycosylated pyrimidine analog containing uracil attached to a ribose ring (or more specifically, a ribofuranose) via a β-N1-glycosidic bond. The analog is one of the five standard nucleosides which make up nucle ...

), which is then incorporated into RNA (a " riboprobe") as it is synthesized by the cellular machinery. It allows to make : * sensitive non-radioactive in situ hybridization probes to detect nucleic acids in plants, able to detect 1 µg of plasmid DNA. * peptide-DIG conjugates, i.e. bradykinin assay by very sensitive chemiluminescence immunoassays. * fluorescent and DIG-labeled tracers for competitive immunoassays, i.e. to limit detect digoxin, a drug used to cure cardiac arrhythmia, down to 0.2 ng mL⁻¹. * Digoxigenin may be conjugated to

sugars Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...

to study

glycosylation Glycosylation is the reaction in which a carbohydrate (or ' glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not al ...

events, even in biological systems.

References

{{Reflist Cardenolides Triols

Use in biotechnology

See also

References