Native-Like and Denatured Cytochrome c Ions Yield Cation-to-Anion Proton Transfer Reaction Products with Similar Collision Cross-Sections.

The relationship between structures of protein ions, their charge states, and their original structures prior to ionization remains challenging to decouple. Here, we use cation-to-anion proton transfer reactions (CAPTR) to reduce the charge states of cytochrome c ions in the gas phase, and ion mobility to probe their structures. Ions were formed using a new temperature-controlled nanoelectrospray ionization source at 25 °C.