The use of silver nanoparticles (Ag NPs) as substrates to obtain satisfactory Raman spectra of native proteins is a simple and valuable but challenging process. Herein, the Ag NPs modified with aluminum and iodide ions (Ag IANPs) were introduced for Raman detection of proteins, including acidic BSA (PI 4.7), catalase (PI 5.4), β-casein (PI 4.5), α-casein (PI 4.0), insulin (PI 5.35), basic myoglobin (PI 6.99), and lysozyme (PI 11.2). The Raman signals of all the detected proteins were significantly improved in comparison with the reported spectra obtained by using Ag NPs containing Na₂SO₄, I^–, and Mg²⁺. Specifically, detection sensitivities of the acidic proteins were drastically increased. The limit of detection (LOD) of bovine serum albumin (BSA), α-casein, and β-casein was 0.03 ng/mL. The LOD of insulin and catalase were 0.3 and 3 ng/mL, respectively. As the bands corresponding to disulfide bonds, α-helices, residues of Phe, Trp, and Tyr, and carboxyl groups were also greatly enhanced, it was easy to monitor the folding of native protein and the denaturation of protein under acidic and heated conditions. Thus, Ag IANPs as substrates open a way for surface-enhanced Raman spectroscopy (SERS) detection of proteins. Hence, the method can provide more valuable information about protein and, therefore, has the potential for wide applications.

中文翻译：

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Ag IANP通过表面增强拉曼光谱技术对天然蛋白进行无标签和高度灵敏的检测

使用银纳米颗粒（Ag NPs）作为底物以获得令人满意的天然蛋白质拉曼光谱是一个简单而有价值的但具有挑战性的过程。本文介绍了用铝和碘离子修饰的Ag NPs（Ag IANPs）用于蛋白质的拉曼检测，包括酸性BSA（PI 4.7），过氧化氢酶（PI 5.4），β-酪蛋白（PI 4.5），α-酪蛋白（PI 4.0），胰岛素（PI 5.35），碱性肌红蛋白（PI 6.99）和溶菌酶（PI 11.2）。与使用含有Na ₂ SO ₄，I ^–和Mg ^2+的Ag NP所获得的光谱相比，所有检测到的蛋白质的拉曼信号均得到了显着改善。。特别地，酸性蛋白质的检测灵敏度大大提高。牛血清白蛋白（BSA），α-酪蛋白和β-酪蛋白的检出限（LOD）为0.03 ng / mL。胰岛素和过氧化氢酶的LOD分别为0.3和3 ng / mL。由于对应于二硫键，α-螺旋，Phe，Trp和Tyr的残基以及羧基的条带也大大增强，因此在酸性和高温条件下易于监测天然蛋白质的折叠和蛋白质的变性。因此，Ag IANPs作为底物为蛋白质的表面增强拉曼光谱（SERS）检测开辟了道路。因此，该方法可以提供有关蛋白质的更有价值的信息，因此具有广泛应用的潜力。