Mass Analysis of Macro-molecular Analytes via Multiply-Charged Ion Attachment.

A novel gas-phase charge and mass manipulation approach is demonstrated to facilitate the mass measurement of high mass complexes within the context of native mass spectrometry. Electrospray ionization applied to solutions generated under native or near-native conditions has been demonstrated to be capable of preserving biologically relevant complexes into the gas phase as multiply charged ions suitable for mass spectrometric analysis. However, charge state distributions tend to be narrow and extensive salt adduction, heterogeneity, and so on tend to lead to significantly broadened peaks. These issues can compromise mass measurement of high mass bio-complexes, particularly when charge states are not clearly resolved. In this work, we show that the attachment of high mass ions of known mass and charge to populations of ions of interest can lead to well-separated signals that can yield confident charge state and mass assignments from otherwise poorly resolved signals.