University of Strathclyde, Department of Physics, Photophysics Group, Centre for Molecular Nanometrology, SUPA, Glasgow, G4 0NG, Scotland.
J Biomed Opt. 2012 Jul;17(7):075001. doi: 10.1117/1.JBO.17.7.075001.
We describe the auto-oxidation of 3, 4-dihydroxy-L-phenylalanine (L-DOPA) in the synthesis of eumelanin to spontaneously produce fibrils upon drying. The self-assembled fibrils are of characteristic diameter ∼1 to 2 μm, composed of filaments, and are unidirectional, apart from branches that are formed at typically an angle of 20 to 22 deg. The fibrils are characterized using fluorescence spectroscopy, fluorescence decay times, scanning electron microscopy, atomic force microscopy, and fluorescence lifetime imaging microscopy. The fibrils mimic natural melanin in consisting of core eumelanin with efficient nonradiative properties, but they also display pockets of electronically isolated species with higher radiative rates on the nanosecond timescale. Eumelanin fibrils formed occasionally in solution are tentatively attributed to a scaffold of bacteria or fungus. Fabricating and characterizing novel synthetic eumelanin structures such as fibrils are of interest in helping to reveal a functional structure for eumelanin, in understanding its photophysics, in learning more about L-DOPA as it is used in the treatment of Parkinson's disease, and in producing novel materials which might embody some of the diverse properties of eumelanin.
我们描述了 3,4-二羟基-L-苯丙氨酸（L-DOPA）在合成真黑素过程中的自动氧化，该氧化会在干燥时自发产生纤维。自组装纤维的特征直径约为 1 到 2 微米，由细丝组成，且是单向的，除了通常以 20 到 22 度的角度形成的分支。使用荧光光谱、荧光衰减时间、扫描电子显微镜、原子力显微镜和荧光寿命成像显微镜对纤维进行了表征。纤维类似于由具有高效非辐射特性的核心真黑素组成的天然黑色素，但它们也显示出具有更高辐射率的电子隔离物种的口袋，其辐射率在纳秒时间尺度上。溶液中偶尔形成的真黑素纤维被暂时归因于细菌或真菌的支架。制造和表征新型合成真黑素结构，如纤维，有助于揭示真黑素的功能结构，了解其光物理特性，更多地了解在帕金森病治疗中使用的 L-DOPA，以及产生可能体现真黑素多样化特性的新型材料。
