Advanced Materials and Healthcare Technologies Division, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom.
National Biofilms Innovation Centre, Biodiscovery Institute and School of Life Sciences, University of Nottingham, Nottingham, United Kingdom.
Biointerphases. 2023 May 1;18(3). doi: 10.1116/6.0002604.
Secondary ion mass spectrometry (SIMS) offers advantages over both liquid extraction mass spectrometry and matrix assisted laser desorption mass spectrometry in that it provides the direct in situ analysis of molecules and has the potential to preserve the 3D location of an analyte in a sample. Polysaccharides are recognized as challenging analytes in the mass spectrometry of liquids and are also difficult to identify and assign using SIMS. Psl is an exopolysaccharide produced by Pseudomonas aeruginosa, which plays a key role in biofilm formation and maturation. In this Letter, we describe the use of the OrbiTrap analyzer with SIMS (3D OrbiSIMS) for the label-free mass spectrometry of Psl, taking advantage of its high mass resolving power for accurate secondary ion assignment. We study a P. aeruginosa biofilm and compare it with purified Psl to enable the assignment of secondary ions specific to the Psl structure. This resulted in the identification of 17 peaks that could confidently be ascribed to Psl fragments within the biofilm matrix. The complementary approach of the following neutral loss sequences is also shown to identify multiple oligosaccharide fragments without the requirement of a biological reference sample.
二次离子质谱（SIMS）在液体提取质谱和基质辅助激光解吸质谱方面具有优势，因为它可以直接对分子进行原位分析，并有可能保留样品中分析物的 3D 位置。多糖被认为是液体质谱分析中的挑战性分析物，使用 SIMS 也很难识别和分配。Psl 是铜绿假单胞菌产生的一种胞外多糖，在生物膜形成和成熟中起着关键作用。在这封信中，我们描述了使用带有 SIMS 的 OrbiTrap 分析仪（3D OrbiSIMS）对 Psl 进行无标记质谱分析，利用其高质量分辨率准确分配二次离子。我们研究了铜绿假单胞菌生物膜，并将其与纯化的 Psl 进行比较，以能够分配特定于 Psl 结构的二次离子。这导致鉴定出 17 个峰，可以自信地将其归因于生物膜基质中的 Psl 片段。还展示了后续中性丢失序列的互补方法，无需生物参考样品即可识别多个低聚糖片段。
