The percent exchange was calculated for each individual sample (exchanged monomer, exchanged fibril, and in-exchange monomer), using no back-exchange correction.
Results are presented as relative levels of deuteration with no correction for back exchange, since no fully deuterated protein sample could be obtained.
All HDX MS results are presented as relative levels of deuterium incorporation and no correction for back exchange is applied, because no fully deuterated protein sample could be obtained.
As mentioned above, no correction for back exchange of the protein was made because all data were used in two-state comparisons of the redox-state samples under identical conditions.
After the time needed to allow the back exchange of fast-exchanging deuterons (approx. 1 h) had elapsed, the peptides were subjected to MS analysis.
No correction was made for back exchange because all values are used in a relative way (used in a two-state comparison) and susceptible to the same back exchange processes.
All HDX data were normalized to 100% deuterium content, and no correction was made for back exchange because relative trends provided the needed information.
A detailed explanation of the effect of incomplete back exchange is provided in the Supplemental Information.
Several established approaches have been used to maximize the back exchange.
However, one drawback of deuteration is the incomplete back exchange of the observable amide hydrogens.
