Amide I vibrational mode suppression in surface (SERS) and tip (TERS) enhanced Raman spectra of protein specimens.
Amide I vibrational mode suppression in surface (SERS) and tip (TERS) enhanced Raman spectra of protein specimens.
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DOI：
10.1039/c2an36478f
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发表时间：
2013-03-21
期刊：
影响因子：
--
通讯作者：
Lednev IK
中科院分区：
文献类型：
--
作者：
Kurouski D;Postiglione T;Deckert-Gaudig T;Deckert V;Lednev IK
表面和针尖增强拉曼光谱（Sers和TERS）是一种现代光谱技术，在生物系统结构表征中显示出巨大的潜力。通过局部表面等离子体共振的拉曼信号的强增强使得能够在单分子尺度上进行化学检测。从生物样品（如肽、蛋白质或微生物）收集的增强拉曼光谱经常观察到缺乏酰胺I带，酰胺I带通常用作解释二级蛋白质结构的标记。几十年来，这种现象的原因一直不清楚。在这项工作中，我们研究了这一现象的天然胰岛素和胰岛素纤维使用TERS和Sers，并比较这些光谱的光谱定义明确的homo肽。结果表明，酰胺I拉曼谱带的出现与蛋白质聚集状态无关，而是由氨基酸侧链的大小决定的。对于短模型肽，TERS和Sers光谱中酰胺I带的缺失与大体积侧链的存在相关。同型甘氨酸和丙氨酸，这是肽与小侧链基团（H和CH 3，分别），表现出强烈的酰胺I带几乎100%的收购光谱。具有庞大侧链的肽，如酪氨酸和色氨酸，分别在70%和31%的所获得的光谱中显示酰胺I带。
Surface- and tip-enhanced Raman spectroscopy (SERS and TERS) are modern spectroscopic techniques, which are becoming widely used and show a great potential for the structural characterisation of biological systems. Strong enhancement of the Raman signal through localised surface plasmon resonance enables chemical detection at the single-molecule scale. Enhanced Raman spectra collected from biological specimens, such as peptides, proteins or microorganisms, were often observed to lack the amide I band, which is commonly used as a marker for the interpretation of secondary protein structure. The cause of this phenomenon was unclear for many decades. In this work, we investigated this phenomenon for native insulin and insulin fibrils using both TERS and SERS and compared these spectra to the spectra of well-defined homo peptides. The results indicate that the appearance of the amide I Raman band does not correlate with the protein aggregation state, but is instead determined by the size of the amino acid side chain. For short model peptides, the absence of the amide I band in TERS and SERS spectra correlates with the presence of a bulky side chain. Homo-glycine and -alanine, which are peptides with small side chain groups (H and CH3, respectively), exhibited an intense amide I band in almost 100% of the acquired spectra. Peptides with bulky side chains, such as tyrosine and tryptophan, exhibited the amide I band in 70% and 31% of the acquired spectra, respectively.
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