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Chlorophyll c refers to forms of chlorophyll found in certain marine algae, including the photosynthetic Chromista (e.g. diatoms and brown algae) and dinoflagellates. These pigments are characterized by their unusual chemical structure, with a porphyrin as opposed to the chlorin (which has a reduced ring D) as the core; they also do not have an isoprenoid tail. Both these features stand out from the other chlorophylls commonly found in algae and plants.

It has a blue-green color and is an accessory pigment, particularly significant in its absorption of light in the 447–520 nm wavelength region. Like chlorophyll a and chlorophyll b, it helps the organism gather light and passes a quanta of excitation energy through the light harvesting antennae to the photosynthetic reaction centre.

Chlorophyll c can be further divided into chlorophyll c₁, chlorophyll c₂, and chlorophyll c₃, plus at least eight other more recently found subtypes.

Chlorophyll c₁

Chlorophyll c₁ is a common form of chlorophyll c. It differs from chlorophyll c₂ in its C8 group, having an ethyl group instead of vinyl group (C-C single bond instead of C=C double bond). Its absorption maxima are around 444, 577, 626 nm and 447, 579, 629 nm in diethyl ether and acetone respectively.

Chlorophyll c₂

Chlorophyll c₂ is the most common form of chlorophyll c. Its absorption maxima are around 447, 580, 627 nm and 450, 581, 629 nm in diethyl ether and acetone respectively.

Chlorophyll c₃

Chlorophyll c₃ is a form of chlorophyll c found in microalga Emiliania huxleyi, identified in 1989. Its absorption maxima are around 452, 585, 625 nm and 452, 585, 627 nm in diethyl ether and acetone respectively.

Biosynthesis

Chlorophyll c synthesis branches off early from the typical Chlorophyllide synthesis pathway, after divinylprotochlorophyllide (DV-PChlide) is formed. It has been established that DV-PChlide and MV-PChlide are processed directly by a 17 oxidase (CHLC, chlorophyll c synthase) into Chl c₂ and Chl c₁, respectively. The 17 oxidtion was proposed to proceed by "hydroxylation of the 17-propionate reside at the 17-position and successive dehydration to the 17-acrylate residue." An 8-vinyl reductase (elaborating on the promiscuous behavior of ferredoxin-type 3,8-divinyl chlorophyllide reductase) could also convert Chl c₂ into Chl c₁. The two steps could be swapped for the same effect.

Structure

Chlorophyll c1	Chlorophyll c2	Chlorophyll c3
Names IUPAC name acrylato(2-)]magnesium Identifiers CAS Number 11003-45-5 c1: 18901-56-9 c2: 27736-03-4 c3: 111308-93-1 3D model (JSmol) Interactive image c1: Interactive image Beilstein Reference 5801077, 6996880 ChEBI CHEBI:38202 ChemSpider 21865345 PubChem CID 25245630 UNII 1A9E276K41 c1: 008W2KH70E c2: 8GAP92KIWW c3: FMN10170B8 InChI InChI=1S/C35H32N4O5.Mg/c1-8-19-15(3)22-12-24-17(5)21(10-11-28(40)41)32(38-24)30-31(35(43)44-7)34(42)29-18(6)25(39-33(29)30)14-27-20(9-2)16(4)23(37-27)13-26(19)36-22;/h8,10-14,31H,1,9H2,2-7H3,(H3,36,37,38,39,40,41,42);/q;+2/p-2/b11-10+,22-12-,23-13-,24-12-,25-14-,26-13-,27-14-,32-30-;Key: DGNIJJSSARBJSH-QRKQXEOSSA-L SMILES CCC1=C(C)/C2=C/c3c(C=C)c(C)c4\C=C5/N=C(C(\C=C\C(O)=O)=C/5C)C5=c6c(C(=O)C5C(=O)OC)c(C)c(=CC1=N\2)n6n34 c1: COC(=O)C9C(=O)c6c(C)c3n7c6c9c2c(C=CC(=O)O)c(C)c1cc5n8c(cc4n(78n12)c(c=3)c(CC)c4c)c(C=C)c5C Properties Chemical formula C35H30MgN4O5 Molar mass 610.953 g·mol Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references Chemical compound	Names IUPAC name acrylato(2-)]magnesium Identifiers CAS Number 27736-03-4 3D model (JSmol) Interactive image Interactive image Beilstein Reference 5801049 6996841 ChEBI CHEBI:38203 ChemSpider 21865346 PubChem CID 16070018 UNII 8GAP92KIWW InChI InChI=1S/C35H30N4O5.Mg/c1-8-19-15(3)22-12-24-17(5)21(10-11-28(40)41)32(38-24)30-31(35(43)44-7)34(42)29-18(6)25(39-33(29)30)14-27-20(9-2)16(4)23(37-27)13-26(19)36-22;/h8-14,31H,1-2H2,3-7H3,(H3,36,37,38,39,40,41,42);/q;+2/p-2/b11-10+,22-12?,23-13?,24-12?,25-14?,26-13?,27-14?,32-30?;Key: QDRBYWCRXZZVLY-JUQUGTHISA-L SMILES CC1=C(C2=CC3=NC(=CC4=C(C5=C(4)C(=C6C(=C(C(=N6)C=C12)C)C=CC(=O)O)C(C5=O)C(=O)OC)C)C(=C3C)C=C)C=C. COC(=O)C9C(=O)c6c(C)c3n7c6c9c2c(C=CC(=O)O)c(C)c1cc5n8c(cc4n(78n12)c(c=3)c(C=C)c4c)c(C=C)c5C Properties Chemical formula C35H28MgN4O5 Molar mass 608.937 g·mol Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references Chemical compound	Identifiers CAS Number 111308-93-1 3D model (JSmol) Interactive image ChemSpider 32699592 PubChem CID 71587417 UNII FMN10170B8 InChI InChI=1S/C36H30N4O7.Mg/c1-8-18-15(3)21-12-22-16(4)20(10-11-27(41)42)32(39-22)30-31(36(45)47-7)34(43)28-17(5)23(40-33(28)30)13-25-19(9-2)29(35(44)46-6)26(38-25)14-24(18)37-21;/h8-14,31,38,43H,1-2H2,3-7H3,(H,41,42);/q;+2/p-2/b11-10+,21-12?,25-13?,26-14?,32-30?;/t31-;/m1./s1Key: CWLZENTWIZFJMW-XUGDHDJXSA-L SMILES CC1=C(C2=NC1=CC3=NC(=C4C(C(=C5C4=NC(=C5C)C=C6C(=C(C(=C2)N6)C(=O)OC)C=C))C(=O)OC)C(=C3C)C=CC(=O))C=C. Properties Chemical formula C36H28MgN4O7 Molar mass 652.946 g·mol Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references Chemical compound

References

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8. ^ Jiang, Yanyou; Cao, Tianjun; Yang, Yuqing; Zhang, Huan; Zhang, Jingyu; Li, Xiaobo (2023-10-06). "A chlorophyll c synthase widely co-opted by phytoplankton". Science. 382 (6666): 92–98. doi:10.1126/science.adg7921.
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• Porphyrins
• Photosynthetic pigments
• Brown algae
• Diatom biology