Fig 3.
Regions of bimodal H/D exchange within IAV HA identified by whole-virus HDX-MS. (A) HDX-MS analysis revealed that the HA peptide 402–418 (part of the HA2 subunit) displayed bimodal activity, and this peptide is highlighted orange on the crystal structure of A/PR8 HA (PDB: 1RU7). (B) Representative spectra of triplicate samples from pH 7 and pH 4 groups showing a mass shift for bimodal peptide 402–418 with increasing D2O incubation times. Mass shift is compared to samples incubated in a non-deuterated buffer (ND). Bimodal envelopes are separated by gray and orange coloring. (C) Proportions of the left (gray) and right (orange) populations are graphed with time. Data indicate the mean ± SD for triplicate samples analyzed by HDX-MS.