Deuterium Substitution and Charge Retention in Ions of Organic and Bioorganic Compounds. Part 2. Apamin Complex

The correspondence between the mass spectral components obtained by the separation of hydrogen/deuterium exchange (HDX) mass spectra of multiply charged ions of the apamin complex and specific structural forms of these ions has been confirmed. As in the case of apamin, the separation method is based on the best approximation of HDX mass spectra of multiply charged ions by a linear combination of several H/D/z peak distributions. These distributions assume independent replacement of exchangeable hydrogen atoms with deuterium and independent retention of z charge carriers. Based on the analysis of the complete set of HDX data for the apamin complex, including cases where the spectra of ions with certain charges were excluded, it is shown that the ion charge has no significant effect on the HDX processes of the major components (with contributions above 3%) during residual deuterium exchange in the apamin complex. In the presence of an ND₃ gas flow, the observed changes for ions with different charges are minor and affect only the contributions of the major HDX mass spectral components, without taking into account the presence and localization of minor components with contributions below 10%.