Fig. P1.

NanoSIMS images of the surface of a Clone 15 fibroblast cell. (A) The ¹⁵N-enrichment image of the entire dorsal surface of the cell shows ¹⁵N-sphingolipid-rich domains within the plasma membrane, evidenced by statistically significant local elevations in the ¹⁵N-enrichment. (B) The secondary electron image that corresponds to the region outlined in A shows the cell has normal morphology. (C) The ¹³C-enrichment image of the same region confirms the membrane was intact and the sample preparation and NanoSIMS imaging did not create artifactual lipid clustering. (D) Domains enriched with ¹⁵N-sphingolipids are visible in the enlarged ¹⁵N-enrichment image of the region outlined in A.