Fig. 1.

3D OrbiSIMS depth profile analysis of frozen hydrated ex vivo human skin tissue. (A) A schematic illustrating the process. (B) An example negative polarity spectrum. The spectrum presents the total ion intensity for the 250 × 250 µm area summed across the whole depth profile (total applied ion dose is 2.88 × 10¹³). Using the SIMS-MFP software, we were able to putatively assign over 140 different species across 5 compound classes (amino acids, fatty acids, ceramides, phospholipids, and triglycerides). The mass regions for these classes are highlighted on the spectrum, and an example compound is labeled for each class, detailing the molecular assignment, chemical formula, and the observed mass (m/z) and deviation. a.u., arbitrary units; FA, fatty acid; Cer, ceramides; TG, triglycerides; PE, phosphatidylethanolamine.