Families
- fluorescent proteins
GFP (green), YFP (yellow) and RFP (red) can be attached to other specific proteins to form a fusion protein, synthesized in cells after tranfection of a suitable plasmid carrier.
- Non-protein organic fluorophores belong to following major chemical families
- Xanthene derivatives: fluorescein, rhodamine, Oregon green, eosin, and Texas red
- Cyanine derivatives: cyanine, indocarbocyanine, oxacarbocyanine, thiacarbocyanine, and merocyanine
- Naphthalene derivatives (dansyl and prodan derivatives)
- Coumarin derivatives
- oxadiazole derivatives: pyridyloxazole, nitrobenzoxadiazole and benzoxadiazole
- Pyrene derivatives: cascade blue etc.
- Oxazine derivatives: Nile red, Nile blue, cresyl violet, oxazine 170 etc.
- Acridine derivatives: proflavin, acridine orange, acridine yellow etc.
- Arylmethine derivatives: auramine, crystal violet, malachite green
- Tetrapyrrole derivatives: porphin, phtalocyanine, bilirubin
These fluorophores fluoresce thanks to delocalized electrons which can jump a band and stabilize the energy absorbed. Benzene, one of the simplest aromatic hydrocarbons, for example, is excited at 254 nm and emits at 300 nm. This discrimates Fluorophores from quantum dots, which are fluorescent semiconductor nanoparticles.
- They can be attached to protein to specific functional groups, such as
- amino groups (Active ester, Carboxylate, Isothiocyanate, hydrazine) - carboxyl groups (carbodiimide) - thiol (maleimide, acetyl bromide) - azide (via click chemistry or non-specifically (glutaraldehyde)).
Additionally, various functional groups can be present to alter its proprerties, such as solubility, or confer special proprieties, such as boronic acid which binds to sugars or multiple carboxyl groups to bind to certain cations. When the dye contains an electron-donating and an electron-accepting group at opposite ends of the aromatic system, this dye will probably be sensitive to the environment's polarity (solvatochromic), hence called environment-sensitive. Often dyes are used inside cells, which are impermeable to charged molecules, as a result of this the carboxyl groups are converted into an ester, which is removed by esterases inside the cells, e.g., fura-2AM and fluorescein-diacetate.
The following dye families are trademark groups, and do not necessarily share structural similarities.
- CF dye (Biotium)
- BODIPY (Invitrogen)
- Alexa Fluor (Invitrogen)
- DyLight Fluor (Thermo Scientific, Pierce)
- Atto and Tracy (Sigma Aldrich)
- FluoProbes (Interchim)
- DY and MegaStokes Dyes (Dyomics)
- Sulfo Cy dyes (CYANDYE, LLC)
- Setau and Square Dyes (SETA BioMedicals)
- Quasar and Cal Fluor dyes (Biosearch Technologies)
- SureLight Dyes (APC, RPE, PerCP, Phycobilisomes)(Columbia Biosciences])
- APC, APCXL, RPE, BPE (Phyco-Biotech)
A few examples of commonly used dyes:
Read more about this topic: Fluorescent Dyes
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