Effects of ultra violet radiation on the soluble proteins of human hair

• UVR enhanced elution of hair proteins and decreased their tryptophan fluorescence.
• UVR enhanced quantity of soluble hair proteins and their SH-content.
• Protein elution decreased SH-content of residual soluble proteins in hair fiber.
• Quantity of soluble proteins in distal parts of the hair fiber increased.
• Thiols and tryptophan fluorescence of proteins decreased from the proximal to distal parts.

Exposure of hair fibers from healthy volunteers to Ultra Violet Radiation (UVR) under laboratory conditions enhanced protein elution from the hair tresses into a buffer solution (pH 10.5). At the same time the UVR decreased the intensity of tryptophan fluorescence in the eluted proteins. After mechanical homogenization of these hair samples, the increase of soluble protein was registered for UVR treated hair as well as the rise in sulfhydryl group content of these proteins.Analysis of soluble proteins from hair samples homogenized before and after protein elution has shown that mainly proteins rich in sulfhydryl groups were eluted and as a result sulfhydryl content of proteins in hair shaft decreased. The hypothesis concerning the effects of environmental factors on the properties of hair shaft proteins was examined, the proximal and distal parts of normal hair (0–5 cm and 15–20 cm from hair root) were compared. In the distal parts there was a higher quantity of soluble proteins registered after homogenization, with decreased sulfhydryl group content and tryptophan fluorescence. It could be supposed that this difference results from the steady rupture of cystine in sulfur bridges and tryptophan under exposure to environmental factors (mainly, UVR), followed by elution of the resulting peptides.