Recombination Between ¹³C and ²H to Form Acetylide (¹³C₂²H‾) Probes Nanoscale Interactions in Lipid Bilayers Via Dynamic Secondary Ion Mass Spectrometry: Cholesterol and GM₁ Clustering

25 March 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Although it is thought that there is lateral heterogeneity of lipid and protein components within biological membranes, probing this heterogeneity has proven challenging. The difficulty in such experiments is due to both the small length scale over which such heterogeneity can occur, and the significant perturbation resulting from fluorescent or spin labeling on the delicate interactions within bilayers. Atomic recombination during dynamic nanoscale secondary ion imaging mass spectrometry (NanoSIMS) is a non-perturbative method for examining nanoscale bilayer interactions. Atomic recombination is a variation on conventional NanoSIMS imaging whereby an isotope on one molecule combines with a different isotope on another molecule during the ionization process, forming an isotopically enriched polyatomic ion in a distance-dependent manner. We show that the recombinant ion, ¹³C₂²H‾, is formed in high yield from ¹³C- and ²H-labeled lipids. The low natural abundance of triply labeled acetylide has makes it an ideal ion to probe GM₁ clusters in model membranes and the effects of cholesterol on lipid-lipid interactions. We find evidence supporting the cholesterol condensation effect as well as the presence of nanoscale GM₁ clusters in model membranes.


Dynamic Secondary Ion Mass Spectrometry
Membrane Organization

Supplementary materials

Recombination to Form Acetylide Supporting Information
This supporting information contains information on the following: synthesis of 13C18-POPC and 13C18-DSPC, synthesis of 13C18 NHS stearate and 2H35 NHS stearate, synthesis of 13C18-GM1 and 2H35-GM1, examining lower limits of recombination, lipid compositions, optimization of recombination signal, and the concentration dependence of recombination.


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