Figure 1.

Illustration of two proteoform features in an LC-MS map. (a) Elution profiles (curves) of two proteoforms A and B. At time points t₁, t₂, and t₃, three MS1 spectra are generated. The abundances of A have a ratio of 4:3:0 (two red vertical lines), and the abundances of B have a ratio of 0:1:1 (two blue vertical lines). (b) Theoretical isotopic envelopes of proteoform A with charge states 1+ and 2+ and proteoform B with charge state 2+. (c) Three MS1 spectra are generated at time points t₁, t₂, and t₃. The elution profiles on the right are the same as (a). The three spectra contain four experimental isotopic envelopes of A and two envelopes of B.