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==Structure==
[[Porphyrin complexes]] consist of a square planar MN<sub>4</sub> core. The periphery of the porphyrins, consisting of sp<sup>2</sup>-hybridized carbons, generally display small deviations from planarity. "Ruffled" or saddle-shaped porphyrins is attributed to interactions of the system with its environment.<ref>{{cite journal | vauthors = Senge MO, MacGowan SA, O'Brien JM | title = Conformational control of cofactors in nature - the influence of protein-induced macrocycle distortion on the biological function of tetrapyrroles | journal = Chemical Communications | volume = 51 | issue = 96 | pages = 17031–17063 | date = December 2015 | pmid = 26482230 | doi = 10.1039/C5CC06254C | hdl-access = free | hdl = 2262/75305 }}</ref> Additionally, the metal is often not centered in the N<sub>4</sub> plane.<ref>{{cite book |doi=10.1002/9781119951438.eibc0104 |chapter=Iron Porphyrin Chemistry |title=Encyclopedia of Inorganic and Bioinorganic Chemistry |year=2011 | vauthors = Walker FA, Simonis U |isbn=9781119951438 }}</ref> For free porphyrins, the two pyrrole protons are mutually trans and project out of the N<sub>4</sub> plane.<ref> {{cite journal | vauthors = Jentzen W, Ma JG, Shelnutt JA | title = Conservation of the conformation of the porphyrin macrocycle in hemoproteins | journal = Biophysical Journal | volume = 74 | issue = 2 Pt 1 | pages = 753–763 | date = February 1998 | pmid = 9533688 | pmc = 1302556 | doi = 10.1016/S0006-3495(98)74000-7 | bibcode = 1998BpJ....74..753J }}</ref> These nonplanar distortions are associated with altered chemical and physical properties. [[Chlorophyll]]-rings are more distinctly nonplanar, but they are more saturated than porphyrins.<ref>{{Cite journal | vauthors = Senge MO, Ryan AA, Letchford KA, MacGowan SA, Mielke T | year = 2014 | title = Chlorophylls, Symmetry, Chirality, and Photosynthesis | journal = Symmetry | volume = 6 | issue = 3 | pages = 781–843 | doi = 10.3390/sym6030781 | bibcode = 2014Symm....6..781S | doi-access = free | hdl = 2262/73843 | hdl-access = free }}</ref>
==Complexes of porphyrins==
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:H<sub>2</sub>porphyrin + [ML<sub>n</sub>]<sup>2+</sup> → M(porphyrinate)L<sub>n−4</sub> + 4 L + 2 H<sup>+</sup>, where M = metal ion and L = a ligand
<gallery caption="Representative porphyrins and derivatives" widths="140px" heights="
File:PPIXtransH.png|Derivatives of [[protoporphyrin IX]] are common in nature, the precursor to [[heme]]s.
File:H2octaethylporphyrin.png |[[Octaethylporphyrin]] (H<sub>2</sub>OEP) is a synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, OEP<sup>2−</sup> is highly symmetrical.
File:H2TPP.png|[[Tetraphenylporphyrin]] (H<sub>2</sub>TPP)is another synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, TPP<sup>2−</sup> is highly symmetrical. Another difference is that its methyne centers are occupied by phenyl groups.
File:Heme
CP40model.png|A macrocycle of 40 porphyrin molecules, model
CP40-STM.png|A macrocycle of 40 porphyrin molecules, [[scanning tunneling microscope|STM image]]
</gallery>
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=== Biological applications ===
Porphyrins have been investigated as possible anti-inflammatory agents<ref>{{cite journal | vauthors = Alonso-Castro AJ, Zapata-Morales JR, Hernández-Munive A, Campos-Xolalpa N, Pérez-Gutiérrez S, Pérez-González C | title = Synthesis, antinociceptive and anti-inflammatory effects of porphyrins | journal = Bioorganic & Medicinal Chemistry | volume = 23 | issue = 10 | pages = 2529–2537 | date = May 2015 | pmid = 25863493 | doi = 10.1016/j.bmc.2015.03.043 }}</ref> and evaluated on their anti-cancer and anti-oxidant activity.<ref>{{cite journal | vauthors = Bajju GD, Ahmed A, Devi G | title = Synthesis and bioactivity of oxovanadium(IV)tetra(4-methoxyphenyl)porphyrinsalicylates | journal = BMC Chemistry | volume = 13 | issue = 1 | pages = 15 | date = December 2019 | pmid = 31384764 | pmc = 6661832 | doi = 10.1186/s13065-019-0523-9 | doi-access = free }}</ref> Several porphyrin-peptide conjugates were found to have antiviral activity against HIV ''in vitro''.<ref>{{cite journal | vauthors = Mendonça DA, Bakker M, Cruz-Oliveira C, Neves V, Jiménez MA, Defaus S, Cavaco M, Veiga AS, Cadima-Couto I, Castanho MA, Andreu D, Todorovski T | display-authors = 6 | title = Penetrating the Blood-Brain Barrier with New Peptide-Porphyrin Conjugates Having anti-HIV Activity | journal = Bioconjugate Chemistry | volume = 32 | issue = 6 | pages = 1067–1077 | date = June 2021 | pmid = 34033716 | pmc = 8485325 | doi = 10.1021/acs.bioconjchem.1c00123 }}</ref>
=== Toxicology ===▼
Heme biosynthesis is used as [[biomarker]] in environmental toxicology studies. While excess production of porphyrins indicate [[organochlorine]] exposure, [[lead]] inhibits [[ALA dehydratase]] enzyme.<ref>{{Cite book|title=Principles of Ecotoxicology| vauthors = Walker CH, Silby RM, Hopkin SP, Peakall DB |publisher=CRC Press|year=2012|isbn=978-1-4665-0260-4|location=Boca Raton, FL|pages=182}}</ref>▼
==Gallery==
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* Corphins, the highly reduced porphyrin coordinated to nickel that binds the [[Cofactor F430]] active site in [[methyl coenzyme M reductase]] (MCR)
* Nitrogen-substituted porphyrins: [[phthalocyanine]]
▲=== Toxicology ===
▲Heme biosynthesis is used as [[biomarker]] in environmental toxicology studies. While excess production of porphyrins indicate [[organochlorine]] exposure, [[lead]] inhibits [[ALA dehydratase]] enzyme.<ref>{{Cite book|title=Principles of Ecotoxicology| vauthors = Walker CH, Silby RM, Hopkin SP, Peakall DB |publisher=CRC Press|year=2012|isbn=978-1-4665-0260-4|location=Boca Raton, FL|pages=182}}</ref>
== References ==
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