Melanin
Melanins (Greek μέλας ( MELAS ) "black" ) are reddish, brown or black pigments, which result from the enzymatic oxidation of tyrosine (enzymatic browning ) and the effect of the skin, hair, feathers and eyes, except for albinism. They occur in vertebrates and insects, as a colorant in the ink of cuttlefish and also in microorganisms and plants. Made in vertebrates is melanin in the melanocytes of the skin and in the retina and iris of the eye.
Melanin in humans
Melanin occurs in humans, especially in two versions: a brown - blackish ( eumelanin ), which is derived from the amino acids tyrosine and L- dopa and a lighter yellowish -red ( pheomelanin ) variant, which contains sulfur. There are also other color variations, so-called allomelanins resulting from hydroxybenzenes. These are mainly found in plants, fungi and bacteria. Almost always contact the melanins as mixed types and are also linked to lipids or proteins.
The melanin in human skin and the hair are mixed forms of eumelanins and the sulfur-containing phaeomelanins. The mixing ratio of these two types of melanin is co-determines the skin type of a person. The content of pheomelanin is particularly high in deep red hair and takes about brown and black hair from back. The melanin is stimulated by UVB radiation and it probably serves as a light protection from the harmful effects of UV radiation from the sun. One of the main arguments for the UV protection is the observation that heavily pigmented populations to a lesser extent to sonneninduziertem skin cancer ( " melanoma " ) cancer than less pigmented populations. Meanwhile, the photochemical processes which make melanin at an excellent UV filter, has been studied. It has been shown that melanin converts more than 99.9 % of the radiation energy into harmless heat. This is done by the ultrafast internal conversion (s: internal conversion) from the electronically excited state to vibrational states of the molecule. With this ultra- fast conversion, the lifetime of the excited state shortened. This prevents the formation of free radicals. The excited state of the melanin is very short-lived, and therefore it offers an excellent photoprotection.
Red-haired people have a higher probability of developing melanoma. Therefore, it is assumed that this type of melanin protects the skin less efficient.
Due to genetic predisposition or by acquired over time damage to the genetic material may be disturbed, the synthesis of melanin. A reduced formation leads to hypopigmentation. If production is blocked, so missing the color in skin, hair and eyes, resulting in a very bright white skin, an unusually bright hair color and blue, blue-gray or green eyes, and this may appear red depending on the angle of light. One speaks of albinism and referred the affected organisms as albinos. In case of overproduction (hyperpigmentation ) occur more dark spots in the skin (liver spots, freckles ), which can be malignant ( melanoma). The melanin production can be specifically disrupted by the drug Rucinol.
Melanin in fungi
On May 23, 2007, a scientific work under the direction of Arturo Casadevall was published that deals with fungi that are likely to ionizing radiation by melanin into usable energy for your body to convert ( radiotrophe fungi).
Is explicitly acknowledged that the role of melanin is unclear in energy as before. It is clear only that at the coming of samples from the sealed nuclear reactor Unit 4 of the Chernobyl mushrooms
- A higher metabolic rate was given when they were enriched with melanin than in untreated fungi.
- Was detected in the energy changes in the electron configuration of the electron shell of their melanin. This indicates a modified energy level that is expected in the production of energy as well.
- Is observed a four-fold increase in the reduction of NAD when they are irradiated. It is a metabolic process.
- The metabolism of Wangiella dermatitidis and Cryptococcus neoformans was significantly more active than under conventional conditions at a radiation exposure equivalent to approximately the five- hundred times the natural background radiation.