Melanins


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Melanins

 

brown and black (eumelanins) or yellow (pheomelanins) water-insoluble macromolecular pigments.

Melanins, which are widespread in plants and animals, are responsible for the color of the integuments and their derivatives (hair, feathers, scales) in vertebrates, the cuticles in insects, and the rind in some fruits. In vertebrates, melanins are formed in special cells called melanocytes and deposited in the form of granules in which the melanins are bound to proteins (melano-proteins). The precursor of melanins in the body is the amino acid tyrosine, whose oxidation to dihydroxyphenylalanine (dopa) and subsequently to dopa quinone is catalyzed by the enzyme tyrosinase. Further transformations occur without the participation of enzymes and result in the formation of the melanins, whose chemical structures have not yet been established (empirical formula, C77H98O33N14S).

To a large extent, melanins determine the color of human skin, one of the main characteristics of race.

REFERENCES

Lerner, A. B. “Hormones and Skin Color.” Scientific American, 1961, vol. 205, no. 1.
Mason, H. S. “Structure of Melanins.” In Pigment Cell Biology. New York, 1959. Page 563.
Harley-Mason, J. “Melanins.” In Comprehensive Biochemistry, vol. 6. Amsterdam-London-New York, 1965.

E. V. BUDNITSKAIA

References in periodicals archive ?
Galvan says, "Knowing beforehand that different pigments and structures produce different types of colors in feathers, we examined the appearance of the plumage of all species of extant birds and determined if the color patches that they contain are produced by melanins or by other pigmentary elements.
Building on this idea, the researchers experimented with battery designs that use melanin pigments at either the positive or negative terminals; various electrode materials such as manganese oxide and sodium titanium phosphate; and cations such as copper and iron that the body uses for normal functioning.
In the case of both the elytra and the pronota, females tend to have more of those surfaces covered in melanins and the black coloration is more intense than the comparable areas on males.
Melanin is essential for protecting human skin against radiation, but the accumulation of abnormal melanin induces pigmentation disorders, such as melasma, freckles, ephelide, and senile lentigines (Rees 2003).
Thus, IR absorption spectroscopy could be informative about the immediate binding environment of metal ion in melanins.
They analyzed melanins and melanosomes in hair and skin from adult pigmented Argentine llamas, and their results showed that pheomelanins were present in small quantities in each sample.
The fossils may not contain any actual melanin since most organic matter breaks down before fossilizing.
On exposure to sunlight, the human epidermis undergoes gradual tanning as a result of an increase in melanin pigment.
3) and Ito and co-workers (4,5) described methods for quantitative analysis of melanin in hair and other tissues.
Melanin content, tyrosinase activity and Western blot analysis were performed to elucidate the possible underlying mechanisms.
They indicated that melanin can itself play a role in certain chemical processes that damage DNA and other molecules in cells.