Digoxigenin is a hapten, a small molecule with high antigenicity, that is used in many molecular biology applications similarly to other popular haptens such as 2,4-Dinitrophenol, biotin, and fluorescein. Typically, digoxigenin is introduced chemically (conjugation) into biomolecules (proteins, nucleic acids) to be detected in further assays. Kd of the digoxigenin-antibody interaction has been estimated at ~12 nM (compare to Kd~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 (Kd) of 541 (+/- 193) pM.
Anti-digoxigenin antibodies with high affinities and specificity are used in a variety of biological immuno-assays (e.g. ELISA). 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 this case it is conjugated to a single species of RNA nucleoside triphosphate (typically uridine), 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 1μg 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 0.2ng mL−1.
Digoxigenin may be conjugated to sugars to study glycosylation events, even in biological systems.
↑Polya G (2003). Biochemical Targets of Plant Bioactive Compounds. New York: CRC Press. ISBN978-0-415-30829-8.
↑Tetin SY, Matayoshi ED (August 2002). "Measuring antibody affinity and performing immunoassay at the single molecule level". Analytical Biochemistry. 307 (1): 84–91. doi:10.1016/S0003-2697(02)00011-8. PMID12137783.
↑Eisel D, Grünewald-Janho S, Krushen B, eds. (2002). DIG Application Manual for Nonradioactive in situ Hybridization (3rded.). Penzberg: Roche Diagnostics.
↑Hauptmann G, Gerster T (August 1994). "Two-color whole-mount in situ hybridization to vertebrate and Drosophila embryos". Trends in Genetics. 10 (8): 266. doi:10.1016/0168-9525(90)90008-T. PMID7940754.
↑Décarie A, Drapeau G, Closset J, Couture R, Adam A (1994). "Development of digoxigenin-labeled peptide: application to chemiluminoenzyme immunoassay of bradykinin in inflamed tissues". Peptides. 15 (3): 511–8. doi:10.1016/0196-9781(94)90214-3. PMID7937327. S2CID19210640.
↑Mayilo S, Ehlers B, Wunderlich M, Klar TA, Josel HP, Heindl D, Nichtl A, Kürzinger K, Feldmann J (July 2009). "Competitive homogeneous digoxigenin immunoassay based on fluorescence quenching by gold nanoparticles". Analytica Chimica Acta. 646 (1–2): 119–22. Bibcode:2009AcAC..646..119M. doi:10.1016/j.aca.2009.05.023. PMID19523564.
↑Goodarzi MT, Rafiq M, Turner G (May 1995). "An improved multiwell immunoassay using digoxigenin-labelled lectins to study the glycosylation of purified glycoproteins". Biochemical Society Transactions. 23 (2): 168S. doi:10.1042/bst023168s. PMID7672194.