178 JOURNAL OF COSMETIC SCIENCE 10 Gauss Figure 6. ESR spectrum of the DMPO-OH adduct from irradiated hair. A 0.015-g sample of hair was irradiated for 10 min in 1 ml 20 mM DMPO, after which the sample solution phase was transferred to the quartz fiat cell. Spectrometer settings: microwave power, 20 mw sweep width, 100 G modulation am- plitude, 1 G receiver gain, 1.25 x 104 number of scans, 5. a. DMPO blank (no hair). b. Brown hair. c. Red hair. d. Bleached hair. oxidations. Additional reactions result in the oxidation of amino acids, most notably tryptophan, within the hair matrix. Thus, photodamaged hair (and wool) is characterized by reduced tryptophan and increased cysteic acid (5,6,50,41). The reduced fiber strength of weathered hair appears to be the consequence of the scission of disulfide bonds and their conversion to cysteic acid residues. Tryptophan photodamage appears to precede disulfide photooxidation. In cysteine-containing protein such as keratin, the disulfide bond contributes strongly to the overall stability and integrity of the structure. With the destruction of disulfide bonds, the hair may lose its natural elasticity, become more porous, and, hence, become more sensitive to changes in humidity. Degradation of

OXYRADICALS FROM PHOTOIRRADIATED HAIR 179 10 Gauss Figure 7. Effect of cinnamic acid on the DMPO adduct from irradiated red hair: 0.02 g red hair in 1 ml of 20 mM DMPO solution. The spectrometer settings are the same as in Figure 6. a. No irradiation. b. Irradiated for 10 min. c. 10 mM cinnamic acid added, irradiated for 10 min. Propagation: RS' + 02 • RSOO' RSOO' + RSH • RSOOH + RS- RS' + RSH • RSSR'- + H + RSSR'- + 02 • RSSR + 02'- 02 + RSH • H202 + RS'- Reduction of hydrogen peroxide: RSSR-- + H202 • RSSR + OH- + OH Termination: 2RS' --- RSSR RS' + RSSR'- • RSSR + RS- 202'- + 2H + • H202 + 02 Scheme 2