Editing Green fluorescent protein (section)

== Other fluorescent proteins ==
[[File:Fluorescence from Fluorescent Proteins.jpg|alt=A rack of test tubes showing solutions glowing in different colors|thumb|Different proteins produce different fluorescent colors when exposed to ultraviolet light.]]

There are many GFP-like proteins that, despite being in the same protein family as GFP, are not directly derived from ''Aequorea victoria''. These include [[dsRed]], eqFP611, Dronpa, TagRFPs, KFP, EosFP/IrisFP, Dendra, and so on. Having been developed from proteins in different organisms, these proteins can sometimes display unanticipated approaches to chromophore formation. Some of these, such as KFP, are developed from naturally non- or weakly-fluorescent proteins to be greatly improved upon by mutagenesis.<ref>{{cite journal | vauthors = Chudakov DM, Belousov VV, Zaraisky AG, Novoselov VV, Staroverov DB, Zorov DB, Lukyanov S, Lukyanov KA | title = Kindling fluorescent proteins for precise in vivo photolabeling | journal = Nature Biotechnology | volume = 21 | issue = 2 | pages = 191–4 | date = February 2003 | pmid = 12524551 | doi = 10.1038/nbt778 | s2cid = 52887792 }}</ref> When GFP-like barrels of different spectra characteristics are used, the excitation spectra of one chromophore can be used to power another chromophore (FRET), allowing for conversion between wavelengths of light.<ref>{{cite journal | vauthors = Wiens MD, Shen Y, Li X, Salem MA, Smisdom N, Zhang W, Brown A, Campbell RE | title = A Tandem Green-Red Heterodimeric Fluorescent Protein with High FRET Efficiency | journal = ChemBioChem | volume = 17 | issue = 24 | pages = 2361–2367 | date = December 2016 | pmid = 27781394 | doi = 10.1002/cbic.201600492 | s2cid = 4301322 }}</ref>

[[FMN-binding fluorescent proteins]] (FbFPs) were developed in 2007 and are a class of small (11–16 kDa), oxygen-independent fluorescent proteins that are derived from blue-light receptors. They are intended especially for the use under anaerobic or hypoxic conditions, since the formation and binding of the Flavin chromophore does not require molecular oxygen, as it is the case with the synthesis of the GFP chromophore.<ref name = "Drepper">{{cite journal | vauthors = Drepper T, Eggert T, Circolone F, Heck A, Krauss U, Guterl JK, Wendorff M, Losi A, Gärtner W, Jaeger KE | title = Reporter proteins for in vivo fluorescence without oxygen | journal = Nature Biotechnology | volume = 25 | issue = 4 | pages = 443–445 | date = April 2007 | pmid = 17351616 | doi = 10.1038/nbt1293 | s2cid = 7335755 }}</ref>

[[File:White Light Image of Fluorescent Proteins.jpg|thumb|White light image, or image seen by the eye, of fluorescent proteins in image above.]]

Fluorescent proteins with other chromophores, such as UnaG with bilirubin, can display unique properties like red-shifted emission above 600&nbsp;nm or photoconversion from a green-emitting state to a red-emitting state. They can have excitation and emission wavelengths far enough apart to achieve conversion between red and green light.

A new class of [[fluorescent protein]] was evolved from a [[cyanobacteria]]l (''[[Trichodesmium erythraeum]]'') [[phycobiliprotein]], α-[[allophycocyanin]], and named small ultra [[red fluorescent protein]] ([[smURFP]]) in 2016. [[smURFP]] [[Catalysis|autocatalytically]] self-incorporates the [[chromophore]] [[biliverdin]] without the need of an external [[protein]], known as a [[lyase]].<ref name=":0">{{cite journal | vauthors = Rodriguez EA, Tran GN, Gross LA, Crisp JL, Shu X, Lin JY, Tsien RY | title = A far-red fluorescent protein evolved from a cyanobacterial phycobiliprotein | journal = Nature Methods | volume = 13 | issue = 9 | pages = 763–9 | date = September 2016 | pmid = 27479328 | pmc = 5007177 | doi = 10.1038/nmeth.3935 }}</ref><ref>{{cite book | vauthors = Mattson S, Tran GN, Rodriguez EA |chapter=Directed Evolution of Fluorescent Proteins in Bacteria |date=2023 |title=Fluorescent Proteins |series=Methods in Molecular Biology |volume=2564 |pages=75–97 | veditors = Sharma M |place=New York, NY |publisher=Springer US |language=en |doi=10.1007/978-1-0716-2667-2_4 |isbn=978-1-0716-2666-5 |pmid=36107338 }}</ref> [[Jellyfish]]- and [[coral]]-derived GFP-like proteins require [[oxygen]] and produce a [[Stoichiometry|stoichiometric]] amount of [[hydrogen peroxide]] upon [[chromophore]] formation.<ref>{{cite journal | vauthors = Tsien RY | s2cid = 8138960 | title = The green fluorescent protein | journal = Annual Review of Biochemistry | volume = 67 | issue = 1 | pages = 509–44 | date = 1998-01-01 | pmid = 9759496 | doi = 10.1146/annurev.biochem.67.1.509 }}</ref> [[smURFP]] does not require [[oxygen]] or produce [[hydrogen peroxide]] and uses the [[chromophore]], [[biliverdin]]. [[smURFP]] has a large [[Molar attenuation coefficient|extinction coefficient]] (180,000 M<sup>−1</sup> cm<sup>−1</sup>) and has a modest [[quantum yield]] (0.20), which makes it comparable biophysical brightness to [[eGFP]] and ~2-fold brighter than most red or far-red [[fluorescent protein]]s derived from [[coral]]. [[smURFP]] spectral properties are similar to the organic dye [[Cy5]].<ref name=":0" /><ref>{{cite journal | vauthors = Maiti A, Buffalo CZ, Saurabh S, Montecinos-Franjola F, Hachey JS, Conlon WJ, Tran GN, Hassan B, Walters KJ, Drobizhev M, Moerner WE, Ghosh P, Matsuo H, Tsien RY, Lin JY, Rodriguez EA | title = Structural and photophysical characterization of the small ultra-red fluorescent protein | journal = Nature Communications | volume = 14 | issue = 1 | pages = 4155 | date = July 2023 | pmid = 37438348 | pmc = 10338489 | doi = 10.1038/s41467-023-39776-9 | bibcode = 2023NatCo..14.4155M }}</ref>
[[File:E. coli expressing fluorescent proteins.jpg|thumb|296x296px|E. coli colonies expressing fluorescent proteins.]]
Reviews on new classes of fluorescent proteins and applications can be found in the cited reviews.<ref>{{cite journal | vauthors = Rodriguez EA, Campbell RE, Lin JY, Lin MZ, Miyawaki A, Palmer AE, Shu X, Zhang J, Tsien RY | title = The Growing and Glowing Toolbox of Fluorescent and Photoactive Proteins | journal = Trends in Biochemical Sciences | volume = 42 | issue = 2 | pages = 111–129 | date = February 2017 | pmid = 27814948 | pmc = 5272834 | doi = 10.1016/j.tibs.2016.09.010 }}</ref><ref>{{cite journal| vauthors = Montecinos-Franjola F, Lin JY, Rodriguez EA |date=2020-11-16|title=Fluorescent proteins for in vivo imaging, where's the biliverdin? |journal=Biochemical Society Transactions |volume=48|issue=6|pages=2657–2667 |doi=10.1042/BST20200444 |pmid=33196077|s2cid=226971864 }}</ref>