Probing the heterogeneous structure of eumelanin using ultrafast vibrational fingerprinting
Probing the heterogeneous structure of eumelanin using ultrafast vibrational fingerprinting
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DOI：
10.1038/s41467-020-18393-w
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发表时间：
2020-09-11
影响因子：
16.6
通讯作者：
Kohler, Bern
中科院分区：
文献类型：
--
作者：
Grieco, Christopher;Kohl, Forrest R.;Kohler, Bern
真黑素是一种棕黑色的生物色素，具有防晒和清除自由基的功能，对许多生物体都很重要。真黑素也是一种很有前途的氧化还原活性材料，用于能量转换和存储，但这种异质色素中存在的化学结构尚不清楚，限制了人们对其光响应亚基性质的了解。在这里，我们介绍了一种超快振动指纹图谱方法，用于探测真黑素等非均质材料中发色团的结构和相互作用。具体地说，记录了由通过紫外-可见光谱调谐的超快激发脉冲光选的电子生色团的子集在双键伸展区域的瞬时振动光谱。所有的子集都显示出一个共同的振动指纹，这表明真黑素中不同的电子吸收体，无论跃迁能量如何，都含有相同分布的红外活性官能团。氧化态不同发色团的聚集是真黑素在任何波长的光激发下普遍、超快失活行为的关键结构特性。
Eumelanin is a brown-black biological pigment with sunscreen and radical scavenging functions important to numerous organisms. Eumelanin is also a promising redox-active material for energy conversion and storage, but the chemical structures present in this heterogeneous pigment remain unknown, limiting understanding of the properties of its light-responsive subunits. Here, we introduce an ultrafast vibrational fingerprinting approach for probing the structure and interactions of chromophores in heterogeneous materials like eumelanin. Specifically, transient vibrational spectra in the double-bond stretching region are recorded for subsets of electronic chromophores photoselected by an ultrafast excitation pulse tuned through the UV-visible spectrum. All subsets show a common vibrational fingerprint, indicating that the diverse electronic absorbers in eumelanin, regardless of transition energy, contain the same distribution of IR-active functional groups. Aggregation of chromophores diverse in oxidation state is the key structural property underlying the universal, ultrafast deactivation behavior of eumelanin in response to photoexcitation with any wavelength.