SKIN PIGMENT RENDERS SUN'S UV RADIATION HARMLESS USING PROJECT ILES
Researchers at Lund University in Sweden and
other institutions have worked out how the pigment of the skin manages to
protect the body from the sun's dangerous UV rays. The skin pigment converts
the UV radiation into heat through a rapid chemical reaction that shoots
protons from the molecules of the pigment.
In
a new study, the team from Lund University, working with colleagues in France
and Italy, have studied pigment in the skin and its building blocks. Pigment in
both skin and hair comprises two different types of melanin: eumelanin and
pheomelanin. Eumelanin makes us develop a suntan and gives colour to brown and
black hair, whereas those with red hair and pale skin instead have high levels
of pheomelanin.
"We
found that eumelanin converts harmful UV radiation into heat with almost 100
per cent efficiency. The chemical reaction is incredibly quick, taking less
that a thousandth of a billionth of a second," said Villy Sundström,
Professor of Chemistry at Lund University.
What
happens in detail in the chemical reaction is that a hydrogen ion -- a proton
-- is ejected from the pigment at the same moment the UV light reaches the
pigment molecule. The chain of events could be likened to the melanin getting
rid of the energy of the UV light by very quickly shooting a proton projectile.
This projectile in turn gives off energy to the surrounding membrane tissue in
the form of heat. It has therefore converted dangerous UV energy into harmless
heat.
"In
this way, the pigment disarms the energy in the UV light and prevents it
causing harmful chemical reactions," said Villy Sundström.
Eumelanin
is considered to be the pigment that protects against UV radiation while
pheomelanin is believed to cause skin cancer in some way, which explains why
people with red hair are more likely to develop malignant melanoma. However, researchers
have not previously been aware of what chemical reactions UV light causes in
the pigment. There has therefore also been a lack of knowledge of the pigment
processes that lead to protection against or development of cancer.
"By
understanding how the body naturally protects itself against UV light, we can
develop better sun protection products based on the same principles. This would
provide better protection against skin cancer," said Villy Sundström.
The
idea is also in the long run to find treatment methods and substances that
replace natural pigment for those with defective production of eumelanin.
Eumelanin is composed of two similar building blocks, but only one of them
produces the protective effect. This shows that the effect is very specific --
it is a matter of small differences in the chemical structure of the building
blocks. This insight could prove important in the development of substances for
treatment and sun protection products.
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