Since Ar-gas cluster ion beams (Ar-GCIBs) have been introduced into time-of-flight secondary ion mass spectrometry (ToF-SIMS), there have been various attempts to analyze organic materials and biomolecules that require low-damage analysis and high sensitivity, because Ar-GCIBs allow soft ionization of large molecules such as peptides and proteins due to the low energy per atom. Here, the authors adopted the Ar-GCIB as a primary beam to detect proteins including human insulin, ubiquitin, and cytochrome C (molecular weights are 5808, 8564, and 12 327 Da, respectively). They have confirmed that the detection of the intact proteins was possible when the Ar-GCIB was used as a primary ion beam. In addition, they successfully identified each protein by analyzing the trypsin-digested peptides in myoglobin, cytochrome C, and bovine serum albumin. They also attempted on-surface enzymatic digestion to identify proteins on the surface of the Si wafer and obtained results identical to those of in-solution digestion. It is expected that the authors’ on-surface digestion method can enable the application of ToF-SIMS for the analysis of proteins present in biological tissues.

中文翻译：

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ToF-SIMS中的Ar-气体团簇离子束，用于肽和蛋白质分析。

自从将氩气簇离子束（Ar-GCIBs）引入飞行时间二次离子质谱（ToF-SIMS）以来，人们已经进行了各种尝试来分析需要低损伤分析和高分离度的有机材料和生物分子。由于Ar-GCIB由于每个原子的能量较低，因此允许大分子（如肽和蛋白质）的软电离，因此具有高灵敏度。在这里，作者采用Ar-GCIB作为主要光束来检测包括人胰岛素，泛素和细胞色素C（分子量分别为5808、8564和12327 Da）的蛋白质。他们已经确认，将Ar-GCIB用作主要离子束时，可以检测完整蛋白。此外，他们通过分析肌红蛋白，细胞色素C和牛血清白蛋白中胰蛋白酶消化的肽，成功鉴定出每种蛋白质。他们还尝试了表面酶消化以鉴定Si晶片表面上的蛋白质，并获得了与溶液内消化相同的结果。预期作者的表面消化方法可以使ToF-SIMS应用于分析生物组织中存在的蛋白质。