Figure 2. Comparing mass spectra from pure lowicryl at varying laser energy.

(a) Mass spectra of lowicryl collected at 30 pJ (black), 200 pJ (red), and 450 pJ (blue) UV laser energies. Each spectrum is normalised to the same peak intensity of the 12C+ peak and contains approximately 10 M, 4 M, and 2 M. Total counts, respectively. A zoomed in region centered at (b) 14 Da and (c) 56 Da where 14N and 56Fe are expected, respectively. Since ferritin is not present in these pure lowicryl specimens, the observed peaks 14 and 56 Da are attributed to organic species.