Wilczok T, Bilińska B, Buszman E, Kopera M
Arch Biochem Biophys. 1984 Jun;231(2):257-62. doi: 10.1016/0003-9861(84)90386-2.
The infrared and electron spin resonance spectra of synthetic 3,4-dihydroxyphenylalanine (DOPA) and tyrosine melanins and chemically modified melanin samples were determined, and it was shown that unmodified and reduced DOPA melanins exhibited similar ir spectra. Oxidized DOPA melanins showed a higher number of carboxy groups in the sample. A significant increase of free radical content in reduced DOPA melanin and a decrease of free radical content in oxidized DOPA melanin in comparison to unmodified samples were demonstrated by the use of ESR methodology. Methylation of tyrosine melanin with an excess of diazomethane gave very rich ir spectra as compared to melanins methylated with methanol saturated by gaseous HCl. In tyrosine melanin samples the esterification of carboxy groups with methanol caused a decrease in the free radical content. When diazomethane was used, the methylated melanin samples had free radical levels reduced to only about 4% of the total observed for unmodified tyrosine melanin.
测定了合成的3,4 - 二羟基苯丙氨酸（DOPA）黑色素、酪氨酸黑色素以及化学修饰黑色素样品的红外光谱和电子自旋共振光谱，结果表明未修饰和还原的DOPA黑色素呈现相似的红外光谱。氧化的DOPA黑色素样品中羧基数量更多。通过电子自旋共振方法证明，与未修饰样品相比，还原的DOPA黑色素中自由基含量显著增加，而氧化的DOPA黑色素中自由基含量减少。与用气态HCl饱和的甲醇甲基化的黑色素相比，用过量重氮甲烷对酪氨酸黑色素进行甲基化得到的红外光谱非常丰富。在酪氨酸黑色素样品中，羧基与甲醇的酯化导致自由基含量降低。当使用重氮甲烷时，甲基化的黑色素样品的自由基水平降低至仅约为未修饰酪氨酸黑色素中观察到的总量的4%。
