State Key Laboratory of Physical Chemistry of Solid Surfaces, ‡The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, and §Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University , Xiamen 361005, China.
Anal Chem. 2014 Feb 18;86(4):2238-45. doi: 10.1021/ac403974n. Epub 2014 Feb 5.
Proteins perform vital functional and structural duties in living systems, and the in-depth investigation of protein in its native state is one of the most important challenges in the postgenomic era. Surface-enhanced Raman spectroscopy (SERS) can provide the intrinsic fingerprint information of samples with ultrahigh sensitivity but suffers from the reproducibility and reliability issues. In this paper, we proposed an iodide-modified Ag nanoparticles method (Ag IMNPs) for label-free detection of proteins. The silver nanoparticles provide the huge enhancement to boost the Raman signal of proteins, and the coated iodide layer offers a barrier to prevent the direct interaction between the proteins and the metal surface, helping to keep the native structures of proteins. With this method, highly reproducible and high-quality SERS signals of five typical proteins (lysozyme, avidin, bovine serum albumin, cytochrome c, and hemoglobin) have been obtained, and the SERS features of the proteins without chromophore were almost identical to the respective normal Raman spectra. This unique feature allows the qualitative identification of them by simply taking the intensity ratio of the Raman peaks of tryptophan to phenylalanine residues. We further demonstrated that the method can also be used for label-free multiplex analysis of protein mixture as well as to study the dynamic process of protein damage stimulated by hydrogen peroxide. This method proves to be very promising for further applications in proteomics and biomedical research.
蛋白质在生命系统中执行重要的功能和结构任务，而在基因组后时代，深入研究蛋白质的天然状态是最重要的挑战之一。表面增强拉曼光谱（SERS）可以提供具有超高灵敏度的样品的固有指纹信息，但存在重现性和可靠性问题。在本文中，我们提出了一种碘化物修饰的银纳米粒子方法（Ag IMNPs）用于蛋白质的无标记检测。银纳米粒子提供了巨大的增强作用，以提高蛋白质的拉曼信号，而涂层的碘化物层提供了一个屏障，以防止蛋白质与金属表面的直接相互作用，有助于保持蛋白质的天然结构。使用这种方法，已经获得了五种典型蛋白质（溶菌酶、亲和素、牛血清白蛋白、细胞色素 c 和血红蛋白）的高度重现性和高质量 SERS 信号，并且没有生色团的蛋白质的 SERS 特征几乎与各自的正常拉曼光谱相同。通过简单地取色氨酸残基与苯丙氨酸残基的拉曼峰的强度比，就可以对它们进行定性鉴定。我们进一步证明，该方法还可用于蛋白质混合物的无标记多重分析以及研究过氧化氢刺激的蛋白质损伤的动态过程。该方法在蛋白质组学和生物医学研究中的进一步应用中证明非常有前景。
