Chemical Imaging of Lipid Domains by High-ResolutionSecondary Ion Mass Spectrometry (HR-SIMS)

Mary Kraft†, Peter Webber§, Ian Hutcheon § Marjorie Longo‡ & Steven Boxer†, †Stanford University, §Lawrence Livermore National Lab & ‡UC Davis

Stanford MRSEC, DMR-0213618

SiO2 on Si

12C15N-

from15N-DLPC

12C15N-

+13C1H-

Phase separated supported lipid bilayers were chemically imaged by HR-SIMS performed with the NanoSIMS 50 (Cameca Instruments). A focused Cs+ ion beam is rastered across the sample, extensively fragmenting the surface components. Secondary ions of up to 5 different masses are simultaneously detected and a lateral resolution of 50 nm can be achieved. In our experiments, a unique stable isotope was selectively incorporated into each membrane component, and the intensity and location of the isotopically enriched secondary ions were used to create a component-specific image of the phase separated lipid bilayer.

AFM

13C1H-

from13C18-DSPC

DLPC (Tm = -5 ºC)fluid phase

15N-DLPC 12C15N-

DSPC (Tm = 55 ºC)gel phase

13C18-DSPC 13C1H-