As mentioned earlier, deconvolution analysis of samples analysed with an MS resolving power of 45K showed the presence of a feature with a mass of VP3 -≈19.5 Da, corresponding to a mass of 59953.83, 59953.88, and 59954.11 in analyses performed at 25°C, 45°C, and 60°C, respectively (See Table ). The two most realistic suggestions from the BPF deconvolution results, based on the peptide mapping results, are the presence of 1x oxidation and 2x succinimide D modifications or the presence of a single succinimide D modification. As discussed earlier, the presence of oxidation would generate a distinct retention time shift from that of unmodified VP3 as well as most likely generate a broad chromatographic peak. However, here we see a comparatively sharp chromatographic peak with no discernible retention time shift between this mass and unmodified VP3 (Figure ). There is potential that the ringed formation of the succinimide modifications can counteract the retention time shift that occurs due to the oxidation PTM, as literature has shown that similarly ringed structures have a similar, but opposite retention time shift from that of oxidized PTMs . However, it is beyond the scope of this study to determine if this is the case here. The minimal retention time shift can also be indicative of the presence of only succinimide, as previous studies have illustrated that succinimide products only minimally separate from their unmodified counterparts . Only succinimide D was detected during peptide mapping above 1%, so if this is the case, that is the succinimide present.