Room‐Temperature Infrared Spectroscopy Combined with Mass Spectrometry Distinguishes Gas‐Phase Protein Isomers

Abstract

Differential IR spectra of gas-phase proteins at room temperature can be obtained by a combination of IR multiphoton dissociation (IRMPD) and FT ion cyclotron resonance mass spectrometry. This new approach yields unique spectra for all-L and singly D-substituted isomers of the protein Trp-cage (see depicted differential spectrum) and thus avoids possible unfolding of proteins during IR irradiation that can affect conventional IRMPD measurements.