melanin

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melanin

(mĕl`ənĭn), water-insoluble polymer of various compounds derived from the amino acid tyrosinetyrosine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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. It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotenecarotene
, long-chained, unsaturated hydrocarbon found as a pigment in many higher plants, particularly carrots, sweet potatoes, and leafy vegetables. Carotene is thought to assist in trapping light energy for photosynthesis or to aid in chemical reduction.
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, which contributes yellow coloring. The synthesis of melanin reactions is catalyzed by the enzyme tyrosinase; an inherited lack of tyrosinase activity results in one of the forms of albinism. Tyrosinase is found in only one specialized type of cell, the melanocyte, and in this cell melanin is found in membrane-bound bodies called melanosomes. Melanosomes can be transferred from their site of synthesis in the melanocytes to other cell types. The various hues and degrees of pigmentation found in the skin of human beings are directly related to the number, size, and distribution of melanosomes within the melanocytes and other cells. Besides it role in pigmentation, melanin, which absorbs ultraviolet light, plays a protective role when skin is exposed to the damaging rays of the sun (see sunburnsunburn,
inflammation of the skin caused by actinic rays from the sun or artificial sources. Moderate exposure to ultraviolet radiation is followed by a red blush, but severe exposure may result in blisters, pain, and constitutional symptoms.
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; skin cancerskin cancer,
malignant tumor of the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma.
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).

melanin

[′mel·ə·nən]
(biochemistry)
Any of a group of brown or black pigments occurring in plants and animals.

melanin

any of a group of black or dark brown pigments present in the hair, skin, and eyes of man and animals: produced in excess in certain skin diseases and in melanomas
References in periodicals archive ?
Liebler finds most convincing the test-tube experiments with eumelanin that show that it has antioxidant properties.
The presentation, "Nonlinear High-Resolution Imaging of Eumelanin and Pheomelanin Distributions in Normal Skin Tissue and Melanoma" is at 8:45 a.
If eumelanin confers greater resistance to feather-degrading bacteria and abrasion than phaeomelanin, then these environmental factors may select for gray feathers at the southern and western periphery of the species' range.
Most scientists agree the development of black skin occurred in early humans primarily because of the ability of eumelanin to effectively absorb ultraviolet radiation.
Skin cells produce two types of pigment - dark brown eumelanin and red/orange pheomelanin.
The pigment, eumelanin, is one of the colouring agents responsible for brown eyes and dark hair in many modern species, including humans.
Melanotropic ligands such as a-melanocyte-stimulating hormone and adrenocorticotropic hormone act via MC1R and regulate the proportion of the photo-protective melanins eumelanin and pheomelanin, which may contribute to ultraviolet (UV) radiation-induced skin damage (1) by favoring the synthesis of eumelanin.
117-121) Eumelanin is characterized by the presence of paramagnetic centers that are solely of the semiquinone type, while pheomelanin contains a hyperfine structure with an unpaired electron near the nucleus of [sup.
Most redheads lack a skin pigment called eumelanin, making them more likely to burn in the sun, and ten times more likely to get skin cancer.
Melanogenesis is a biochemical process that stimulates the production of eumelanin, the dark pigment of the skin which is known to protect the body from skin damage as a result of exposure to both UV-A and UV-B radiation.
In the chicken, the MC1R gene plays a key role in the regulation of eumelanin (black/brown) and pheomelanin (red/yellow) feather pigmentation (Robbins et al.