Influence of Hydration on Dihydroxyacetone-Induced Pigmentation of Stratum Corneum  Bach-Cuc Nguyen, Irene E. Kochevar  Journal of Investigative Dermatology  Volume 120, Issue 4, Pages 655-661 (April 2003) DOI: 10.1046/j.1523-1747.2003.12089.x Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Reactions of DHA with amino groups leading to pigment formation. Journal of Investigative Dermatology 2003 120, 655-661DOI: (10.1046/j.1523-1747.2003.12089.x) Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Influence of RH on the fluorescence of products formed between DHA and murine epidermis. (A) Relative fluorescence spectra obtained upon excitation at 490nm of murine epidermal samples treated with DHA at various RH for 24h. (B) Relative fluorescence at 550nm of DHA-initiated pigment formed in murine epidermis ex vivo at different RH. Data shown are from one experiment of three that all gave a similar pattern. Journal of Investigative Dermatology 2003 120, 655-661DOI: (10.1046/j.1523-1747.2003.12089.x) Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 Effect of preincubation of murine epidermis at various RH on development of DHA-initiated pigmentation. Relative fluorescence intensities were measured at 550nm upon excitation at 490nm. (A) Epidermal samples were equilibrated at 84% RH for 24h, and then DHA was applied and samples were re-incubated at 0% (84–0), 84% (84–84), and 100% (84–100) RH and fluorescence was measured at various times. (B) Epidermal samples were equilibrated at either 0% (0–100), 84% (84–100), or 100% (100–84) RH for 24h, and then DHA was applied and samples were re-incubated at 84% RH and fluorescence was measured at various times. Data shown are from one experiment of three that gave similar patterns. Journal of Investigative Dermatology 2003 120, 655-661DOI: (10.1046/j.1523-1747.2003.12089.x) Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Influence of RH on formation of fluorescent products between DHA and lysine in PVA films. Fluorescence was excited at 340nm. The heavy line indicates samples first incubated at 0%, 75%, 90%, or 100% RH that were treated with DHA and then re-incubated at the same RH. The thin line indicates samples treated with DHA and then incubated at 0%, 75%, 90%, or 100% RH. (A) Time course for development of fluorescence in DHA-treated PVA films containing lysine and incubated at 75% RH. (B) Comparison of development of fluorescence intensity upon excitation at either 340nm or 490nm in lysine-PVA films coated with DHA and held at 75% RH. (C) Relative fluorescence spectra of products formed after 46h of incubation of DHA-treated PVA films containing lysine at varying RH. (D) Relative maximal fluorescence intensity at 424nm at varying times (0, 6, 20, and 46 h) plotted as a function of RH. Data shown are from one experiment of three with similar results. Journal of Investigative Dermatology 2003 120, 655-661DOI: (10.1046/j.1523-1747.2003.12089.x) Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Relationship of percentage water content with efficiency of DHA reaction. (A) Effect of percentage water content in mixed ethylene glycol-aqueous buffer solvent on formation of products between DHA and lysine. The absorption at 340nm is shown as a function of water content after 3, 4, and 5h of incubation at room temperature. Data are from one experiment of three that all gave similar results. (B) Relationship between fluorescent product formation from reaction of DHA with murine epidermis as a function of the water content of the epidermis. Fluorescence was measured at 550nm with excitation at 490nm. These are the same data as shown in Fig 2(B). Journal of Investigative Dermatology 2003 120, 655-661DOI: (10.1046/j.1523-1747.2003.12089.x) Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions