Advancing Orbitrap Measurements of Collision Cross Sections to Multiple Species for Broad Applications

Measurement of collision cross section (CCS), a parameter reflecting an ion's size and shape, alongside high-resolution mass analysis extends the depth of molecular analysis by providing structural information beyond molecular mass alone. Although these measurements are most commonly undertaken using a dedicated ion mobility cell coupled to a mass spectrometer, alternative methods have emerged to extract CCSs directly by analysis of the decay rates of either time-domain transient signals or the FWHM of frequency domain peaks in FT mass analyzers. This information is also accessible from FTMS mass spectra obtained in commonly used workflows directly without the explicit access to transient or complex Fourier spectra. Previously, these experiments required isolation of individual charge states of ions prior to CCS analysis, limiting throughput. Here we advance Orbitrap CCS measurements to more users and applications by determining CCSs from commonly available mass spectra files as well as estimating CCS for multiple charge states simultaneously and showcase these methods by the measurement of CCSs of fragment ions produced from collisional activation of proteins.

Automated summary

Measurement of collision cross section (CCS) is a parameter reflecting the size and shape of an ion and provides structural information beyond molecular mass alone. Previously, isolation of individual charge states was required for CCS analysis, limiting throughput. In this study, CCSs were determined from commonly available mass spectra files using an Orbitrap mass spectrometer, allowing for simultaneous estimation of CCS for multiple charge states and expanding the applicability of this method.