CHEMICAL AND PHOTO-OXIDATIVE HAIR DAMAGE 391 MW 116/97.4 66 45 31 21.5 14.4 6.5 .. Figure 8. Electrophoretic separation of proteins of hair exposed to combinations of chemical and photo- chemical treatments. much less extractable as a result of increasing UV exposure. This suggests UV-radiation- induced crosslinking of the intermediate-filament proteins, turning them into insoluble, less extractable, high-molecular-weight proteins. Permed hair (lane 7) again shows a decrease in the amount of extracted intermediate- filament proteins, while the matrix proteins can still be extracted. Comparing lanes 7 and 8, it can be seen that the amount of extracted protein decreases even further in permed/UV-exposed fibers. This may suggest that not only perming, but also UV radiation, can turn the intermediate-filament proteins into less extractable, high- molecular-weight proteins. Hair fibers exposed to a combination of short-term bleaching followed by perming (lane 9) show high amounts of extractable matrix, intermediate-filament, and high-molecular- weight proteins. This means that the combination of short-term bleaching and perming modifies the hair proteins in a similar way to the long-term four-hour bleaching of the hair sample. In both treatments, severe modifications of the hair proteins into soluble and extractable protein fragments had occurred. The effect of bleaching dominates. A second study takes an additional step and looks at the effects of additional treatment combinations on the main classes of hair proteins: (1) Large amounts of easily soluble/extractable matrix, intermediate-filament, and high- molecular-weight proteins had been formed in hair fibers exposed to a combination of treatments involving bleaching followed by perming. The question we want to answer

392 JOURNAL OF COSMETIC SCIENCE here is whether subsequent UV radiation will crosslink and/or fuse these soluble/ extractable proteins and convert them into less soluble, and therefore, less extractable high-molecular-weight proteins. (2) The readily extractable intermediate-filament and high-molecular-weight proteins of the four-hour-bleached hair fibers had become much less extractable as a result of possible crosslinking during increasing UV exposure. The question we want to answer in this study is whether subsequent peroxide bleaching of these originally bleached/ UV-exposed fibers will again form readily soluble and thus easily extractable proteins, which had been obtained during the first bleaching sequence. UV-radiation-induced crosslinking of hair proteins. Figure 9 shows the separation patterns from hair subjected to dual treatments. Lane 9 shows typical protein bands of the broad-range standard (reference). The readily extractable intermediate-filament and high-molecular-weight proteins of the four-hour-bleached hair fibers (lane 4) had be- come much less extractable as a result of increasing UV exposure (lane 5). It had been suggested that UV irradiation may crosslink and/or fuse matrix and intermediate- filament proteins, turning them into insoluble and less extractable high-molecular- weight proteins. It was theorized that a post-bleaching treatment with peroxide of these already bleached and UV-exposed fibers would degrade the UV-radiation-induced crosslinked and/or fused matrix and intermediate-filament proteins and turn them again 2• 116197.4 66 45 31 21.S 14.4 6.S Figure 9. Electrophoretic separation o.f the main classes of proteins of hair exposed to combinations of chemical and photochemical treatments.