Editing Melanin (section)

=== Eumelanin ===
[[File:Eumelanine.svg|thumb|Part of the structural formula of eumelanin. "(COOH)" can be COOH or H, or (more rarely) other [[substituent]]s. The arrow denotes where the polymer continues.]]
Eumelanin ({{lit|true melanin}}) has two forms linked to [[5,6-dihydroxyindole]] (DHI) and [[DHICA|5,6-dihydroxyindole-2-carboxylic acid]] (DHICA). DHI-derived eumelanin is dark brown or black and insoluble, and DHICA -derived eumelanin which is lighter and soluble in alkali. Both eumelanins arise from the oxidation of tyrosine in specialized organelles called [[Melanosome|melanosomes]]. This reaction is catalyzed by the enzyme [[tyrosinase]]. The initial product, [[L-Dopaquinone|dopaquinone]] can transform into either 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI and DHICA are oxidized and then polymerize to form the two eumelanins.<ref name="Alaluf Heath Carter Atkins 2001 pp. 337–3472"/> 

In natural conditions, DHI and DHICA often co-polymerize, resulting in a range of eumelanin polymers. These polymers contribute to the variety of melanin components in human skin and hair, ranging from light yellow/red pheomelanin to light brown DHICA-enriched eumelanin and dark brown or black DHI-enriched eumelanin. These final polymers differ in solubility and color.<ref name="Alaluf Heath Carter Atkins 2001 pp. 337–3472"/> 

Analysis of highly pigmented ([[Fitzpatrick scale|Fitzpatrick type]] V and VI) skin finds that DHI-eumelanin comprises the largest portion, approximately 60–70%, followed by DHICA-eumelanin at 25–35%, and pheomelanin only 2–8%. Notably, while an enrichment of DHI-eumelanin occurs in during [[sun tanning]], it is accompanied by a decrease in DHICA-eumelanin and pheomelanin.<ref name="Alaluf Heath Carter Atkins 2001 pp. 337–3472">{{Cite journal |last1=Alaluf |first1=Simon |last2=Heath |first2=Alan |last3=Carter |first3=Nik |last4=Atkins |first4=Derek |last5=Mahalingam |first5=Harish |last6=Barrett |first6=Karen |last7=Kolb |first7=Ria |last8=Smit |first8=Nico |date=2001 |title=Variation in Melanin Content and Composition in Type V and VI Photoexposed and Photoprotected Human Skin: The Dominant Role of DHI |journal=Pigment Cell Research |volume=14 |issue=5 |pages=337–347 |doi=10.1034/j.1600-0749.2001.140505.x |issn=0893-5785 |pmid=11601655}}</ref> A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of eumelanin in the absence of other pigments causes blond hair.<ref>{{Cite journal |last1=Ito |first1=S. |last2=Wakamatsu |first2=K. |date=December 2011 |title=Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin |journal=Journal of the European Academy of Dermatology and Venereology |volume=25 |issue=12 |pages=1369–1380 |doi=10.1111/j.1468-3083.2011.04278.x |issn=1468-3083 |pmid=22077870 |s2cid=5121042}}</ref> Eumelanin is present in the skin and hair, etc.