FPOP was performed with 15% exclusion volume, 100 mM H2O2, in 100 μm ID capillary. (A.) Volcano plot of FPOP results, using oxidation at room temperature as the reference sample. Each point represents one peptide from the biosimilar, with the X-axis representing the fold change in oxidation amount after heat shock as compared to the reference, and the Y-axis representing the p-value from a two-tailed Student’s t-test. The four shaded regions represent statistically significant changes in oxidation (α = 0.05), with the shade representing the color coding used in the structural visualization. (B.) Structural visualization of the differential FPOP data plotted in the volcano plot. Cyan: <2x decrease in oxidation; Blue: >2x decrease in oxidation; Magenta: <2x increase in oxidation; Red: >2x increase in oxidation; Grey: regions of the protein where no oxidized peptide was detected in any sample. Regions that showed no statistically significant changes in oxidation are colored green (light chain) or yellow (heavy chain).