{{Short description|Natural emission of light by biological structures}} [[Image:PaperAutofluorescence.jpg|thumb|300px|[[Micrograph]] of paper autofluorescing under [[ultraviolet]] illumination. The individual fibres in this sample are around 10 [[micrometre|μm]] in diameter.]] '''Autofluorescence''' is the natural [[fluorescence]] of biological structures ('''autofluorophores''')<ref name=":0">{{Cite journal |last=Campbell |first=Jared M. |last2=Gosnell |first2=Martin |last3=Agha |first3=Adnan |last4=Handley |first4=Shannon |last5=Knab |first5=Aline |last6=Anwer |first6=Ayad G. |last7=Bhargava |first7=Akanksha |last8=Goldys |first8=Ewa M. |date=2024-06-12 |title=Label‐Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications |url=https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202403761 |journal=Advanced Materials |language=en |volume=36 |issue=42 |doi=10.1002/adma.202403761 |issn=0935-9648 |archive-url=http://web.archive.org/web/20250611122824/https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202403761 |archive-date=2025-06-11|doi-access=free }}</ref> such as [[mitochondria]] and [[lysosome]]s, in contrast to fluorescence originating from artificially added fluorescent markers ([[fluorophore]]s).<ref name=Monici-2005> {{cite journal |author=Monici, M. |year=2005 |title=Cell and tissue autofluorescence research and diagnostic applications |journal=Biotechnology Annual Review |volume=11 |pages=227–256 |doi=10.1016/S1387-2656(05)11007-2 |pmid=16216779 |isbn=9780444519528 }} </ref>
The most commonly observed autofluorescencing molecules are [[NADPH]] and [[flavin group|flavins]]; the [[extracellular matrix]] can also contribute to autofluorescence because of the intrinsic properties of [[collagen]] and [[elastin]].<ref name=Monici-2005/>
Generally, proteins containing an increased amount of the [[amino acid]]s [[tryptophan]], [[tyrosine]], and [[phenylalanine]] show some degree of autofluorescence.<ref name=Menter-2006/>
Autofluorescence also occurs in non-biological materials found in many papers and textiles. Autofluorescence from U.S. paper money has been demonstrated as a means for discerning counterfeit currency from authentic currency.<ref> {{cite journal |last1=Chia |first1=Thomas |last2=Levene |first2=Michael |date=17 November 2009 |title=Detection of counterfeit U.S. paper money using intrinsic fluorescence lifetime |journal=Optics Express |volume=17 |issue=24 |pages=22054–22061 |doi=10.1364/OE.17.022054 |doi-access=free |pmid=19997451 |bibcode=2009OExpr..1722054C |url=https://zenodo.org/record/894876 }} </ref>
==Microscopy== [[Image:Unmixed Autofluorescence.gif|thumb|300px|A [[multispectral]] image of tissue from a [[mouse]] intestine, showing how autofluoresce can obscure several fluorescence signals.]] Autofluorescence can be problematic in [[fluorescence microscopy]]. Light-emitting [[staining|stains]] (such as fluorescently labelled [[antibody|antibodies]]) are applied to [[Sample (material)|samples]] to enable visualisation of specific structures.
Autofluorescence interferes with detection of specific fluorescent signals, especially when the signals of interest are very dim — it causes structures other than those of interest to become visible.
In some microscopes (mainly [[confocal microscope]]s), it is possible to make use of different lifetime of the [[excited state]]s of the added fluorescent markers and the endogenous molecules to exclude most of the autofluorescence. [[File:Label-free Localisation Microscopy SPDM - Super Resolution Microscopy Christoph Cremer.jpg|left|thumb|300px|Autofluorescence super resolution microscopy/optical nanoscopy image of cellular structures that are invisible with confocal light microscopy]]
In a few cases, autofluorescence may actually illuminate the structures of interest, or serve as a useful [[diagnosis|diagnostic]] indicator.<ref name=Monici-2005/>
For example, cellular autofluorescence can be used as an indicator of [[cytotoxicity]] without the need to add fluorescent markers.<ref name="Fri10">{{cite journal |author1=Fritzsche, M. |author2=Mandenius, C.F. |date=September 2010 |title=Fluorescent cell-based sensing approaches for toxicity testing |journal=Anal Bioanal Chem |volume=398 |issue=1 |pages=181–191 |pmid=20354845 |s2cid=22712460 |doi=10.1007/s00216-010-3651-6 }} </ref>
The autofluorescence of human [[skin]] can be used to measure the level of [[advanced glycation end-product]]s (AGEs), which are present in higher quantities during several human [[disease]]s.<ref name="Ger09"> {{cite journal |author1=Gerrits, E.G. |author2=Smit, A.J. |author3=Bilo, H.J. |date=March 2009 |title=AGEs, autofluorescence and renal function |journal=Nephrol. Dial. Transplant. |volume=24 |issue=3 |pages=710–713 |pmid=19033250 |doi=10.1093/ndt/gfn634 |doi-access=free }} </ref> [[File:BananaSkin40X_Fluorescence.tif|thumb|220px|right|Autofluorescence in [[banana]] skin under different light conditions.]]
[[Optical imaging]] systems that utilize [[multispectral]] imaging can reduce signal degradation caused by autofluorescence while adding enhanced [[multiplexing]] capabilities.<ref>{{cite journal | url=https://dx.doi.org/10.1117/1.2032458 | doi=10.1117/1.2032458 | title=Autofluorescence removal, multiplexing, and automated analysis methods for in-vivo fluorescence imaging | date=2005 | last1=Mansfield | first1=James R. | last2=Gossage | first2=Kirk W. | last3=Hoyt | first3=Clifford C. | last4=Levenson | first4=Richard M. | journal=Journal of Biomedical Optics | volume=10 | issue=4 | page=041207 | pmid=16178631 | bibcode=2005JBO....10d1207M | s2cid=35269802 | doi-access=free }}</ref>
The [[super resolution microscopy]] [[Vertico SMI|SPDM]] revealed autofluorescent cellular objects which are not detectable under conventional fluorescence imaging conditions.<ref> {{cite journal | author1 = Kaufmann, R. | author2 = Müller, P. | author3 = Hausmann, M. | author4 = Cremer, C. | year = 2010 | title = Imaging label-free intracellular structures by localisation microscopy | journal = Micron | volume = 42 | issue = 4 | pages = 348–352 | doi = 10.1016/j.micron.2010.03.006 | pmid = 20538472 }} </ref>
==List of dominant autofluorophores== :{| class="wikitable sortable" style="text-align:center;" |- style="vertical-align:bottom;" !Group ! Molecule ! [[Excited state|Excitation]]<br/>(nm) ! [[Fluorescence]]<br/>(nm) Peak ! {{vertical header| '''Animals''' (Zoae) }} <!-- "Z" for zoae / metazoae --> ! {{vertical header| '''Fungi''' }} <!-- "F" --> ! {{vertical header| '''Plants''' }} <!-- "P" --> <!-- ! {{vertical header| '''Archea''' }} < !-- "A" -- > ! {{vertical header| '''Bacteria''' }} < !-- "B" -- > --> ! {{vertical header| '''Reference''' }} |- | | [[NAD(P)H]] | 340 | 450 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Georgakoudi-Jacobson-etal-2002-02-01> <!-- former ref name=nad --> {{cite journal |author1=Georgakoudi, I. |author2=Jacobson, B.C. |author3=Müller, M.G. |author4=Sheets, E.E. |author5=Badizadegan K. |author6=Carr-Locke, D.L. |author7=Crum, C.P. |author8=Boone, C.W. |author9=Dasari, R.R. |author10=van Dam, J. |author11=Feld, MS |display-authors=6 |date=2002-02-01 |title=NAD(P)H and collagen as ''in vivo'' quantitative fluorescent biomarkers of epithelial precancerous changes |journal=Cancer Research |volume=62 |issue=3 |pages=682–687 |pmid= 11830520 }} </ref> |- | | [[Chlorophyll]] | 465–665 | 673–726 |style="text-align:center;"| |style="text-align:center;"| |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | |- | |[[Collagen]] | 270–370 | 305–450 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Georgakoudi-Jacobson-etal-2002-02-01/> |- | | [[Retinol]] | | 500 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Zipfel-Williams-etal-2003-06-10> <!-- former ref name=liv --> {{cite journal |author1=Zipfel, W.R. |author2=Williams, R.M. |author3=Christie, R. |author4=Nikitin, A.Y. |author5=Hyman, B.T. |author6=Webb, W.W. |date=2003-06-10 |title=Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=100 |issue=12 |pages=7075–7080 |doi=10.1073/pnas.0832308100 |doi-access=free |pmc=165832 |pmid=12756303 |bibcode=2003PNAS..100.7075Z }} </ref> |- | | [[Riboflavin]] | | 550 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Zipfel-Williams-etal-2003-06-10/> |- | | [[Cholecalciferol]] | | 380–460 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Zipfel-Williams-etal-2003-06-10/> |- | | [[Folic acid]] | | 450 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Zipfel-Williams-etal-2003-06-10/> |- | | [[Pyridoxine]] | | 400 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Zipfel-Williams-etal-2003-06-10/> |- | | [[Tyrosine]] | 270 | 305 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Menter-2006> {{cite journal |author=Menter, Julian M. |year=2006 |title=Temperature dependence of collagen fluorescence |journal= Photochemical & Photobiological Sciences |volume=5 |issue=4 |pages=403–410 |pmid=16583021 |doi=10.1039/b516429j |s2cid=34205474 }} </ref> |- | | [[Dityrosine]] | 325 | 400 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Menter-2006/> |- | | Excimer-like<br/>aggregate<br/>(collagen) | 270 | 360 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Menter-2006/> |- | | Glycation adduct | 370 | 450 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Menter-2006/> |- | | [[Indolamine]] | | |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| |style="text-align:center;"| <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | |- | | [[Lipofuscin]] | 410–470 | 500–695 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Schönenbrücher-etal-2008> {{cite journal |author1=Schönenbrücher, Holger |author2=Adhikary, Ramkrishna |author3=Mukherjee, Prasun |author4=Casey, Thomas |author5=Rasmussen, Mark |author6=Maistrovich, Frank |author7=Hamir, Amir |author8=Kehrli, Marcus |author9=Richt, Jurgen |author10=Petrich, Jacob |display-authors=6 |year=2008 |title=Fluorescence-based method, exploiting lipofuscin, for real-time detection of central nervous system tissues on bovine carcasses |journal=Journal of Agricultural and Food Chemistry |volume=56 |issue=15 |pages=6220–6226 |doi=10.1021/jf0734368 |pmid=18620407 |url=https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1548&context=chem_pubs }} </ref> |- | | [[Lignin]]<br/>(a [[polyphenol]]) | 335–488 | 455–535 |style="text-align:center;"| |style="text-align:center;"| |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref> {{cite journal |author1=Donaldson, Lloyd |author2=Williams, Nari |date=February 2018 |title=Imaging and spectroscopy of natural fluorophores in pine needles |journal=Plants |volume=7 |issue=1 |page=10 |doi=10.3390/plants7010010 |doi-access=free |pmid=29393922 |pmc=5874599 }} </ref> |- | | [[Fluorescence spectroscopy#Tryptophan fluorescence|Tryptophan]] | 280 | 300–350 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | |- | |[[Flavin adenine dinucleotide|Flavin]] | 380–490 | 520–560 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | |- | | [[Melanin]] | 340–400 | 360–560 |style="text-align:center;"| '''{{sc|Z}}''' |style="text-align:center;"| '''{{sc|F}}''' |style="text-align:center;"| '''{{sc|P}}''' <!-- |style="text-align:center;"| '''{{sc|A}}''' |style="text-align:center;"| '''{{sc|B}}''' --> | <ref name=Gallas-Eisner-1987-05> {{cite journal |author1=Gallas, James M. |author2=Eisner, Melvin |name-list-style=amp |date=May 1987 |title=Fluorescence of melanin-dependence upon excitation wavelength and concentration |journal= Photochemistry and Photobiology |volume=45 |issue=5 |pages=595–600 |doi=10.1111/j.1751-1097.1987.tb07385.x |s2cid=95703924 }} </ref> |- | rowspan="4" |[[Nicotinamide|Nicotinamides]] |[[Molecular binding|Unbound]] [[Nicotinamide adenine dinucleotide|NADH]] | rowspan="2" |250–300 and 300–380 | rowspan="2" |420–480 | style="text-align: center;" | | | | rowspan="21" |<ref name=":0" /> |- |Unbound [[Nicotinamide adenine dinucleotide phosphate|NADPH]] | | | |- |[[Binding protein|Protein-bound]] NADH | rowspan="2" |Blue shifts ≈20 nm compared to its unbound form | rowspan="2" |Blue shifts ≈20 nm compared to unbound form | | | |- |Protein-bound NADPH | | | |- | rowspan="3" |[[Flavin group|Flavins]] |[[Riboflavin]] (Vitamin B2) | rowspan="3" |210–290 and 325–490 | rowspan="3" |480–625 and 490–600 | | | |- |[[Flavin mononucleotide]] (FMN) | | | |- |[[Flavin adenine dinucleotide]] (FAD<sup>+</sup>) | | | |- |[[Collagen|Collagens]] |[[Collagen#Types|Types 1-28]] |250–450<ref name=":1">Diverse results in literature varying with type, structure, and preparation method</ref> |250–550<ref name=":1" /> | | | |- | rowspan="2" |[[Porphyrin|Porphyrins]] |[[Coproporphyrin I]] |≈360–440 |580–730 | | | |- |[[Protoporphyrin IX]] |350–650 |580–730 | | | |- | rowspan="3" |[[Aromatic amino acid|Aromatic amino acids]] |[[Tyrosine]] |250–325 |300–400 and 500–600 | | | |- |[[Tryptophan]] |250–310 |300–425 | | | |- |[[Dityrosine]] |250–350 |350–410 | | | |- | |[[Elastin]] |300–480 |450–650 | | | |- | |[[A2E]] |250–550 |500–750 | | | |- | |[[Lipofuscin]] |320–480 |400–700 | | | |- | |[[Melanin]] |350–600 |450–800 | | | |- | |[[Keratin]] |365–460 |410–600 | | | |- | rowspan="3" |[[Retinol|Retinols]] |[[Retinol]] |250–380 |414–550 | | | |- |[[Retinol-binding protein]] (RBP) bound to retinol | rowspan="2" |260–400 |250–575 | | | |- |Unbound RBP |250–575 | | | |}
:{{small| Substances luminous in animal tissue are, by taxonomic inclusion, also luminous in [[hominid|human]] tissue.}}
==See also== * [[wikt:autoluminescence|Autoluminescence]] * [[Phosphorescence]] * [[Fluorescence in the life sciences]]
==References== {{reflist}}
[[Category:Microscopy]]