Figure 3.

Deamidation products in Fc IgG. Representative extracted ion chromatogram (EIC) (A) and molecular ion isotope envelopes (B) of IsoD₃₈₂NN (1), NNN (2), a doubly deamidated product (3), ND₃₈₇N (4), and D₃₈₂NN (5) peaks in the EIC, for a sample stressed for 28 h at 37°C, pH 7.4 before digestion. The EIC shows the elution order with IsoD₃₈₂NN eluting first followed by NNN, doubly deamidated and D₃₈₂NN peptides. The isotope envelopes show the +1 amu mass increase for the singly deamidated species and +2 amu for the doubly deamidated product.