Spatial-resolution limits in mass spectrometry imaging of supported lipid bilayers and individual lipid vesicles.
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.
Gunnarsson
Anders
A
Department of Applied Physics, Division of Biological Physics, Chalmers University of Technology, SE-412 96 Goteborg, Sweden.
Kollmer
Felix
F
Sohn
Sascha
S
Höök
Fredrik
F
Sjövall
Peter
P
D006046:Gold / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D018629:Spectrometry, Mass, Secondary Ion
D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D006046:Gold; D012822:Silicon Dioxide; C028694:1-palmitoyl-2-oleoylphosphatidylcholine