Institute for Melanin Chemistry, Fujita Health University, Toyoake, Aichi, Japan.
Curtin Medical School, Faculty of Health Sciences, Curtin University, Perth, WA, Australia.
Photochem Photobiol. 2021 Nov;97(6):1493-1497. doi: 10.1111/php.13511. Epub 2021 Sep 4.
In order to characterize the phenotype and to examine the effects of sun exposure on the color and structure of eumelanin (EM) and pheomelanin (PM) in alpaca fibers, we applied Soluene-350 solubilization, alkaline hydrogen peroxide oxidation (AHPO) and hydroiodic acid (HI) hydrolysis to the base and tip fibers of 20 true-black (TB) and 20 warm-black (WB) alpacas. We analyzed absorbances at 500 nm (A500) and 650 nm (A650), Free and Total pyrrole-2,3,5-tricarboxylic acid (PTCA), 2,3,4,5-tetracarboxylic acid (PTeCA) as degradative products from EM, and 4-amino-3-hydroxyphenylalanine (4-AHP), 3-amino-4-hydroxyphenylalanine (3-AHP) and thiazole-2,4,5-tricarboxylic acid (TTCA) as degradative products from PM. We found that the ratio of PTeCA/Total PTCA increased significantly from the base to the tip in both colors of alpaca fibers, while the ratios of A650/A500 and 4-AHP/3-AHP decreased significantly. These results show that structures made of both EM and PM in alpaca fibers are modified significantly by sun exposure inducing color change. This study indicates that the ratios of A650/A500, PTeCA/Total PTCA and 4-AHP/3-AHP are highly sensitive markers of color change and photodegradation of EM and PM, respectively.
为了描述表型，并研究阳光照射对羊驼纤维中真黑色素（EM）和褐黑色素（PM）的颜色和结构的影响，我们应用 Soluene-350 溶解、碱性过氧化氢氧化（AHPO）和氢碘酸（HI）水解的方法，对 20 只纯黑（TB）和 20 只暖黑（WB）羊驼的毛尖和毛根纤维进行了处理。我们分析了 500nm（A500）和 650nm（A650）的吸光度、游离和总吡咯-2,3,5-三羧酸（PTCA）、2,3,4,5-四羧酸（PTeCA）作为 EM 的降解产物，以及 4-氨基-3-羟基苯丙氨酸（4-AHP）、3-氨基-4-羟基苯丙氨酸（3-AHP）和噻唑-2,4,5-三羧酸（TTCA）作为 PM 的降解产物。我们发现，在两种颜色的羊驼纤维中，从毛根到毛尖，PTeCA/总 PTCA 的比值显著增加，而 A650/A500 和 4-AHP/3-AHP 的比值则显著降低。这些结果表明，在羊驼纤维中，由 EM 和 PM 组成的结构因阳光照射而发生显著变化，导致颜色发生变化。本研究表明，A650/A500、PTeCA/总 PTCA 和 4-AHP/3-AHP 的比值分别是 EM 和 PM 颜色变化和光降解的高度敏感标志物。
