EXPERTS in Glasgow have made a major discovery they hope could pave the way to more effective treatments for skin cancer.
A six-year study by physicists at Strathclyde University has cracked the mystery of how melanin – the naturally occurring pigment in skin, hair and eyes which acts as a sunscreen against ultraviolet rays – is structured.
While the structure of complex materials such as DNA has been known for almost 60 years, the shape of melanin has so far eluded scientists.
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The Strathclyde project, which applied a fluorescent dye to laboratory-made melanin, now suggests the pigment is arranged in a sheet-like structure similar to that of graphite.
The development could offer clues to what causes malignant melanomas to develop in the skin. These tumours, while accounting for just 5% of all skin cancer cases, make up 75% of all deaths from the disease.
The incidence of malignant melanomas in Scotland has rocketed since the mid-1980s, believed to be driven by the effects of increasing exposure to natural and artificial sunlight on foreign holidays and sunbeds.
Between 1985 and 2009, the number of people diagnosed with a malignant melanoma in Scotland rose from 429 to 1181. Although survival rates have improved, over the same period deaths from the tumours climbed from 95 in 1985 to 185 in 2009.
They occur in the body's melanocyte cells – responsible for producing melanin – but it is still unclear what "disturbs" the pigment to bring about melanomas.
Professor David Birch, the photo-physicist who led the research, said: "There's so little known about melanin, but we know that when it absorbs light it can produce harmful free radicals. Free radicals do occur naturally, but they're quite unstable compounds and they'll react with other things. They're known to kill cells. So the feeling is that the production of a free radical by melanin has an effect on the cell and kills it, leading to cancer.
"Now, if we don't know what the structure of melanin is, we don't know really how it's interacting with light – we don't know how free radicals are produced, we don't know whether they're mobile and can move around.
"But if we've demonstrated a sheet structure – which we have – then we can now start looking at what disturbs that structural integrity. We still don't know the detailed structure, but we know it forms sheets. So, for example, melanin is known to bind with metal ions very efficiently, which occur in cells all over the body. Do these metal ions disturb the structural integrity of melanin, or do other things like cholesterol or protein disturb it?
"These things can now be monitored and the effect of these on the structure can be studied quite effectively for the first time, and quite simply, by the method we've used."
The fluorescent dye technique is similar to one used in an earlier research project involving Mr Birch, for a system to detect Alzheimer's disease in its earliest stages.
He now hopes to repeat the experiment with natural melanin.
Mr Birch believes their research will contribute to the development of new treatments for disease.
He said: "We're not clinicians – I'm a physicist that looks at molecules – but we've collaborated with clinicians in the past and we're hoping very much that we can develop the tools that will enable clinicians and medical researchers to have a better handle on these things.
"The detailed structure is still to be confirmed, but this gives an important indication of melanin's make-up from a hitherto unexplored direction. We will be exploring this further and hope to gain more insight into how melanoma occurs."
The research paper is published in the journal Applied Physics Letters.