Redheads remain more susceptible

Differences in how ultraviolet light affects the photochemistry of human pigments may explain why redhaired people are more prone to skin cancer than those with black locks.

John Simon, professor of chemistry at Duke University, Durham, N.C., 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, [which] can produce compounds called radicals that put oxidative stress on cells," he explains. "Such stress could ultimately lead to cancer and other diseases."

Simon found that the pigment produced by cells in black-haired individuals has an oxidation potential "indicating that it's thermodynamically unfavorable for black melanosomes to activate oxygen." 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."

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