Supplemental Figure 1. Tandem mass spectrometry identification of arginineSpectra showing the positive identification of arginine in I. hospitalis – N. equitans cells using an authentic standard based on fragmentation at 10V and 20V. The precursor ion of 175.2 was selected using the narrowest window of ± 0.85m/z units and subjected to collision induced dissociation (CID) with N2 gas. The range for the detection of fragments was set to 30-500 m/z units at a rate of six spectra per second. All other parameters for data acquisition were the same as detailed in the manuscript’s methods section.