Surface Enhanced Raman Scattering Selectivity in Proteins Arises from Electron Capture and Resonant Enhancement of Radical Species
Surface Enhanced Raman Scattering Selectivity in Proteins Arises from Electron Capture and Resonant Enhancement of Radical Species
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DOI：
10.1021/acs.jpcc.0c01436
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发表时间：
2020-04-30
影响因子：
3.7
通讯作者：
Schultz, Zachary D.
中科院分区：
文献类型：
--
作者：
Sloan-Dennison, Sian;Zoltowski, Chelsea M.;Schultz, Zachary D.
等离子体增强的拉曼散射是检测和表征活的和动态的生物系统中的蛋白质的强有力的方法。然而，特定残留物的选择性检测/增强以及光谱扩散和波动使生物物质的增强拉曼光谱和图像的解释复杂化。在这项工作中，我们证明了氨基酸色氨酸（Trp）可以从激发的等离子体中捕获电子，从而产生共振增强的自由基阴离子：充电时可见的激发电子状态滑入共振。这种表面增强共振拉曼散射（SERRS）机制解释了蛋白质的Sers和TERS光谱中Trp特征的持久性。这幅图的证据包括在紫外-可见消光光谱中观察到的可见共振，基态振动光谱的变化和等离子体共振依赖行为。DFT计算支持实验观察。从游离色氨酸分子观察到的行为被示出来解释色氨酸笼蛋白的Sers光谱。实际上，来自通过等离子体激元激发形成的自由基的共振拉曼散射表示可以用于化学感测应用的研究不足的机制。
Plasmon-enhanced Raman scattering is a powerful approach to detecting and characterizing proteins in live and dynamic biological systems. However, the selective detection/enhancement of specific residues as well as spectral diffusion and fluctuations have complicated the interpretation of enhanced Raman spectra and images of biological matter. In this work, we demonstrate that the amino acid tryptophan (Trp) can capture an electron from an excited plasmon, which generates a radical anion that is resonantly enhanced: a visible excited electronic state slides into resonance upon charging. This surface enhanced resonance Raman scattering (SERRS) mechanism explains the persistence of Trp signatures in the SERS and TERS spectra of proteins. Evidence for this picture includes the observation of visible resonances in the UV-vis extinction spectrum, changes in the ground state vibrational spectrum, and plasmon-resonance dependent behavior. DFT calculations support the experimental observations. The behavior observed from the free Trp molecule is shown to explain the SERS spectrum of the Trp-cage protein. In effect, resonant Raman scattering from radicals formed through plasmonic excitation represents an under-investigated mechanism that may be exploited for chemical sensing applications.