Following DNA damage or repair from UV light exposure, we increase the production of melanin and this creates a tanning effect. In mammals, it is known that more than genes have a role in pigmentation.
There is evidence that in addition to its photoprotective qualities, melanin can also be toxic to cells grown in culture dishes after UV exposure. Specifically, melanin can produce reactive oxygen compounds that can lead to a break in a single strand of DNA, and pheomelanin can generate hydrogen peroxide which may cause mutations.
Whether this happens in human skin and whether it impacts cancer is unknown at this time. In recent years, melanin research has expanded from studies aimed at understanding how melanin protects us from UV light to a variety of applied disciplines including materials science, drug delivery, and electronics.
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All rights reserved. Always consult your doctor about your medical conditions. Use of the site is conditional upon your acceptance of our terms of use. What is Melanin? By Editorial Team August 20, Share to Facebook Share to Twitter email print page Bookmark for later comment 0 Reactions 0 reactions. Why is melanin important? How does melanin protect us from UV rays and skin cancer?
How are race, melanin, and skin cancer connected? How does UV light impact skin pigmentation? The formation of a four-carbon ring between the pyrimidines makes it difficult for DNA replication enzymes to determine what base pairs should be across from the fused pyrimidines. A copying mistake like this can change how the DNA encodes a protein, resulting in an abnormal protein.
If the mutation occurs in an area which codes DNA repair enzymes or tumor suppressing proteins, this mutation could lead to cancer. Ultraviolet rays can also damage DNA indirectly.
The story starts with melanin, a class of compounds which organisms produce that give their skin color. The large system of freely-moving delocalized electrons that gives melanin its color is also what allows it to absorb UV light.
Melanin isn't the only light-absorbing compound in living things; chlorophylls and other bright pigments in plants also absorb light, acting in photosynthesis because of the large number of delocalized electrons in each molecule.
When melanin is hit by a photon of UV light, it goes into an excited state, where an electron has increased in energy. In chlorophylls, this excited state starts the chain of reactions that results in photosynthesis. Melanin is different. Instead of becoming very reactive when hit by UV light, melanin releases the extra energy as heat; it reacts less than 1 out of every times it becomes excited.
Occasionally, this protection doesn't work as intended. Ultraviolet radiation can either cause melanin to react or hit a molecule which isn't built to dissipate the energy, like an amino acid. When this happens, the excited molecule can excite an adjacent oxygen atom, turning the stable molecule into a reactive species. Oxygen is much less stable in its excited, higher energy state, so it will react with any proteins or lipids it collides with in the cell in order to go back to its more stable, lower energy state.
Although it can damage various molecules in the cell, the most damage occurs when it hits DNA. When an excited oxygen hits DNA, it can cause a guanine to thymine transversion, which means that the purine guanine is replaced by the pyrimidine thymine.
As in the case of direct DNA damage, this mutation alters how the DNA is translated into a protein and can be potentially harmful.
Part of what makes this type of DNA damage particularly dangerous is that it is caused by excited oxygen molecules, not the UV light itself.
Excited oxygen has an unusually long lifespan for a reactive species, so the damage can occur in cells other than skin cells. Damage can also arise if the excited oxygen collides with a molecule of hydrogen peroxide - the same compound in household disinfectant.
Hydrogen peroxide is produced in the mitochondria as a by-product of cellular respiration. The cell usually turns the peroxide into water, but some molecules escape this process. If an excited oxygen hits hydrogen peroxide, the peroxide splits in half and forms two hydroxyl radicals.
Hydroxyl radicals are a hydrogen atom bonded to an oxygen atom with an unpaired electron this is what makes it a radical. Electrons always prefer being in pairs, so having an unpaired electron makes a compound very reactive. The hydroxyl radical can attach to the backbone of DNA deoxyribose , which can cause the DNA strand to break or a base pair to be released.
Both of these outcomes can be very harmful to the DNA or the cell. Learn about the risks of photosensitivity and how to keep yourself safe. Though less common, Black people can get skin cancer. For this reason, skin cancer is often diagnosed later in Black people and may be more advanced…. A survey by an online pharmacy reports that about a quarter of sunscreen products contain the carcinogen benzene. Is there any evidence for micellar water cancer?
Learn what research suggests and what alternatives to use if you're concerned about this popular…. A large number of Americans aren't aware of how sun exposure can raise their risk of skin cancer. Health Conditions Discover Plan Connect. How Melanin Can Hurt Us. Examining Melanin in the Dark. Protecting Our Skin Inside and Outside. Lupus and Sun Exposure. Read this next.
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