数据之源，洞见之始

Metabolite Card

Note

Dermal melanin is produced by melanocytes, which are found in the stratum basale of the epidermis. Although human beings generally possess a similar concentration of melanocytes in their skin, the melanocytes in some individuals and races more frequently or less frequently express the melanin-producing genes, thereby conferring a greater or lesser concentration of skin melanin. Some individual animals and humans have no or very little melanin in their bodies, which is a condition known as albinism. Higher eumelanin levels also can be a disadvantage, however, beyond a higher disposition toward vitamin D deficiency. Dark skin is a complicating factor in the laser removal of port-wine stains. Effective in treating fair skin, lasers generally are less successful in removing port-wine stains in Asians and people of African descent. Higher concentrations of melanin in darker-skinned individuals simply diffuse and absorb the laser radiation, inhibiting light absorption by the targeted tissue. Melanin similarly can complicate laser treatment of other dermatological conditions in people with darker skin. Under the microscope melanin is brown, non-refractile and finely granular with individual granules having a diameter of less than 800 nanometers. This differentiates melanin from common blood breakdown pigments which are larger, chunky and refractile and range in color from green to yellow or red-brown. In heavily pigmented lesions, dense aggregates of melanin can obscure histologic detail. A dilute solution of potassium permanganate is an effective melanin bleach. Pigments causing darkness in skin, hair, feathers, etc. They are irregular polymeric structures and are divided into three groups: allomelanins in the plant kingdom and eumelanins and phaeomelanins in the animal kingdom. Because melanin is an aggregate of smaller component molecules, there are a number of different types of melanin with differing proportions and bonding patterns of these component molecules. Both pheomelanin and eumelanin are found in human skin and hair, but eumelanin is the most abundant melanin in humans, as well as the form most likely to be deficient in albinism. Freckles and moles are formed where there is a localized concentration of melanin in the skin. They are highly associated with pale skin. Melanin is a biopolymer and a neuropeptide. In the early 1970s, John McGinness, Peter Corry, and Peter Proctor reported that melanin is a high-conductivity organic semiconductor (Science, vol 183, 853-855 (1974)). Studies revealed that melanin acted as a voltage-controlled solid-state threshold switch. Further, it emitting a flash of light electroluminescence when it switched.