Redheads and Skin Cancers

January 31, 2006

Redheads have long recognized--sometimes painfully--that they need to stay out of the sun because they burn more easily. Now Duke chemists have used lasers, microscopes, and clever analysis to explain how sun exposure could make redheads more prone to skin cancer than people with black hair.

John Simon, George B. Geller Professor of chemistry, and his collaborators used a broadly tunable ultraviolet laser and a special microscope to distinguish between the oxidation potentials of pigments of redheaded and black-haired people. Oxidation potentials measure how likely chemicals are to activate oxygen by taking up electrons.

"We were very interested in determining if there are differences in the ability of the two kinds of human pigments to activate oxygen," Simon says. "Activating oxygen can produce compounds called radicals that put oxidative stress on cells. Such stress could ultimately lead to cancer and other diseases."

In their talk at a meeting of the American Chemical Society, the researchers described how they were able for the first time to compare the chemical characteristics of red and black skin pigments. Previously, researchers have been unable to isolate the natural pigments that are contained in skin structures called melanosomes.

Other researchers also had been unable to measure the oxidation potential of the pigments--a hurdle that the Duke chemists overcame by using the highly tunable laser at Duke's Free-Electron Laser Laboratory (FELL). They combined the laser with a microscope at FELL that could resolve the tiny pigment granules.

The group found that the pigment produced by cells in black-haired people has an oxidation potential "indicating that it's thermodynamically unfavorable for black melanosomes to activate oxygen," Simon says. By contrast, "we found it is thermodynamically favorable for red melanosomes to activate oxygen."

"This is the first measurement to ever be reported that compared the two human pigments, and also clearly links the red pigments to possible oxidative stress through their electrochemical properties."