Surface Characterization of Insulin Protofilaments and Fibril Polymorphs Using Tip-Enhanced Raman Spectroscopy (TERS)
Surface Characterization of Insulin Protofilaments and Fibril Polymorphs Using Tip-Enhanced Raman Spectroscopy (TERS)
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DOI：
10.1016/j.bpj.2013.10.040
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发表时间：
2014-01-07
影响因子：
3.4
通讯作者：
Lednev, Igor K.
中科院分区：
文献类型：
--
作者：
Kurouski, Dmitry;Deckert-Gaudig, Tanja;Lednev, Igor K.
淀粉样原纤维是富含β折叠的蛋白质聚集体，其与多种神经退行性疾病（例如阿尔茨海默病和帕金森病）强烈相关。即使这种原纤维的二级结构得到了很好的表征，对其表面组织的透彻理解仍然是难以捉摸的。尖端增强拉曼光谱（TERS）是少数几种可以直接表征淀粉样蛋白原纤维表面的氨基酸组成和蛋白质二级结构的技术之一。在此，我们研究了两种胰岛素原纤维多晶型物的表面，其具有平坦（平坦）和左扭曲（扭曲）形态。结果发现，两者在氨基酸组成和蛋白质二级结构上都有很大差异。例如，Tyr、Pro和His的量不同，相应表面上羧基的数量也不同，而Phe以及带正电荷的氨基和亚氨基的量保持相似。此外，还利用TERS研究了成熟的扁平纤维和扭曲纤维的前体--原丝的表面。结果表明，相对于成熟的原纤维的实质性差异。氨基酸频率和蛋白质二级结构的原丝表面上，并在平面和扭曲的原纤维的相关性，使我们能够提出一个假设的机制，为特定的原纤维多态性的传播。这些知识可以揭示淀粉样蛋白的毒性，并确定纤维多态性的关键因素。最后，这项工作表明了潜在的TERS淀粉样纤维的表面表征的多晶型物。
Amyloid fibrils are beta-sheet-rich protein aggregates that are strongly associated with a variety of neurodegenerative maladies, such as Alzheimer's and Parkinson's diseases. Even if the secondary structure of such fibrils is well characterized, a thorough understanding of their surface organization still remains elusive. Tip-enhanced Raman spectroscopy (TERS) is one of a few techniques that allow the direct characterization of the amino acid composition and the protein secondary structure of the amyloid fibril surface. Herein, we investigated the surfaces of two insulin fibril polymorphs with flat (flat) and left-twisted (twisted) morphology. It was found that the two differ substantially in both amino acid composition and protein secondary structure. For example, the amounts of Tyr, Pro, and His differ, as does the number of carboxyl groups on the respective surfaces, whereas the amounts of Phe and of positively charged amino and imino groups remain similar. In addition, the surface of protofilaments, the precursors of the mature flat and twisted fibrils, was investigated using TERS. The results show substantial differences with respect to the mature fibrils. A correlation of amino acid frequencies and protein secondary structures on the surface of protofilaments and on flat and twisted fibrils allowed us to propose a hypothetical mechanism for the propagation to specific fibril polymorphs. This knowledge can shed a light on the toxicity of amyloids and define the key factors responsible for fibril polymorphism. Finally, this work demonstrates the potential of TERS for the surface characterization of amyloid fibril polymorphs.