Wróbel D, Planner A, Hanyz I, Wielgus A, Sarna T
Molecular Physics Department, Institute of Physics, Poznań, University of Technology, Poland.
J Photochem Photobiol B. 1997 Nov;41(1-2):45-52. doi: 10.1016/s1011-1344(97)00079-1.
Even though melanin is commonly viewed as a photoprotective agent, the molecular mechanism of the melanin-related photoprotective action remains unclear. We studied the interaction of a synthetic dopa melanin with positively and negatively charged porphyrins using an array of spectroscopic techniques. Thus absorption, fluorescence, time-resolved delayed luminescence in the microsecond time range, and photoacoustic spectra at different modulation frequencies of both porphyrins and their mixtures with dopa melanin were measured in buffered aqueous solution at room temperature. It has been confirmed that dopa melanin forms a complex with the cationic porphyrin in its ground state, which significantly modifies the optical properties of the dye molecule. Although no such complex can be detected for the anionic porphyrin, some interaction between melanin and the porphyrin molecule can be detected in its excited state. Both porphyrins show delayed luminescence with a decay time of 35-38 microseconds, which is substantially reduced by melanin. Our photoacoustic measurements indicate that upon photoexcitation, melanin efficiently liberates heat. Our data also suggest that the thermal properties of melanin can be modified by porphyrins, particularly by the cationic form of the dye. The ionic complexes of dopa melanin with the positively charged porphyrin exhibit properties typical for a supermolecular system that liberates heat as a whole.
尽管黑色素通常被视为一种光保护剂，但其相关光保护作用的分子机制仍不清楚。我们使用一系列光谱技术研究了合成多巴黑色素与带正电和负电的卟啉之间的相互作用。因此，在室温下的缓冲水溶液中测量了卟啉及其与多巴黑色素混合物在不同调制频率下的吸收光谱、荧光光谱、微秒时间范围内的时间分辨延迟发光光谱和光声光谱。已证实多巴黑色素在基态下与阳离子卟啉形成复合物，这显著改变了染料分子的光学性质。虽然阴离子卟啉未检测到此类复合物，但在其激发态下可检测到黑色素与卟啉分子之间存在一些相互作用。两种卟啉均显示出延迟发光，衰减时间为35 - 38微秒，黑色素可使其大幅降低。我们的光声测量表明，光激发时，黑色素能有效释放热量。我们的数据还表明，卟啉，特别是染料的阳离子形式，可改变黑色素的热性质。多巴黑色素与带正电卟啉的离子复合物表现出超分子系统的典型性质，即整体释放热量。
