Department of Applied Physics, Division of Biological Physics, Chalmers University of Technology, SE-412 96 Goteborg, Sweden.
Anal Chem. 2010 Mar 15;82(6):2426-33. doi: 10.1021/ac902744u.
The capabilities of time-of-flight secondary ion mass spectrometry (TOF-SIMS) with regards to limits in lateral resolution for biological samples are examined using supported lipid bilayers and individual lipid vesicles, both being among the most commonly used cell membrane mimics. Using supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers confined to a SiO(2) substrate by a chemically modified gold surface, the edge of the lipid bilayer was analyzed by imaging TOF-SIMS to assess the lateral resolution. The results using 80 keV Bi(3)(2+) primary ions show that, under optimized conditions, mass spectrometry imaging of specific unlabeled lipid fragments is possible with sub-100 nm lateral resolution. Comparison of the secondary ion yields for the phosphocholine ion (m/z 184) from a POPC bilayer using C(60)(+) or Bi(3)(+) primary ions showed similar results, indicating an advantage of Bi(3)(+) primary ions for high-resolution imaging of lipid membranes, due to their better demonstrated focusing capability. Moreover, using 300 nm vesicles of different lipid composition, the capability to detect and chemically identify individual submicrometer lipid vesicles at separations down to approximately 1 microm is demonstrated.
利用支持磷脂双层膜和单个脂质囊泡来研究飞行时间二次离子质谱（TOF-SIMS）在生物样品横向分辨率方面的能力，这两种物质都是最常用的细胞膜模拟物。利用化学修饰的金表面将 1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸胆碱（POPC）双层膜限制在 SiO 2 衬底上，通过成像 TOF-SIMS 来分析脂质双层膜的边缘，以评估横向分辨率。使用 80 keV Bi 3+ （2+）初级离子的结果表明，在优化条件下，使用亚 100nm 横向分辨率可以对特定的未标记脂质片段进行质谱成像。使用 C 60+ （+）或 Bi 3+ （2+）初级离子对来自 POPC 双层膜的磷酸胆碱离子（m/z 184）的二次离子产率进行比较，结果相似，这表明 Bi 3+ （2+）初级离子在脂质膜的高分辨率成像方面具有优势，因为它们具有更好的聚焦能力。此外，使用不同脂质组成的 300nm 囊泡，证明了在分离度低至约 1μm 的情况下，能够检测和化学识别单个亚微米脂质囊泡的能力。
