Single-Ion Mass Spectrometry for Heterogeneous and High Molecular Weight Samples

Abstract

In charge detection mass spectrometry (CD-MS) the mass of each individual ion is determined from the measurement of its mass to charge ratio (m/z) and charge. Performing this measurement for thousands of ions allows mass distributions to be measured for heterogeneous and high mass samples that cannot be analyzed by conventional mass spectrometry (MS). CD-MS opens the door to accurate mass measurements for samples into the giga-Dalton regime, vastly expanding the reach of MS and allowing mass distributions to be determined for viruses, gene therapies, and vaccines. Following the success of CD-MS, single-ion mass measurements have recently been performed on an Orbitrap. CD-MS and Orbitrap individual ion mass spectrometry (I 2 MS) are described. Illustrative examples are provided, and the prospects for higher resolution measurements discussed. In the case of CD-MS, computer simulations indicate that much higher resolving powers are within reach. The ability to perform high-resolution CD-MS analysis of heterogeneous samples will be enabling and disruptive in top-down MS as high-resolution m/z and accurate charge measurements will allow very complex m/z spectra to be unraveled.

Protein complex heterogeneity and topology revealed by electron capture charge reduction and surface induced dissociation

“…86 The mass was measured using MP and the mass distribution centered at 510 kDa (see Figure S5A). Charge detection mass spectrometry (CDMS) 8,9,87,11 and the recently commercialized version of CDMS, Direct Mass Technology (DMT) 88 for Orbitrap mass analyzers, enables simultaneous detection of m/z and charge (z) of analytes. This approach is particularly useful for mass determination of very large biomolecules, e.g., for heterogeneous spike proteins and megadalton size viral capsids, where heterogeneity in composition and incomplete desolvation yield very broad and unresolved spectra.…”

Thermal Remodeling of Human HDL Particles Reveals Diverse Subspecies

“…This is especially important when analyzing large, heterogeneous particles because the combination of measurements for each particle eliminates ambiguities when determining the intact mass. Unless one already has prior knowledge of one of the variables ( m or z ) neither can be inferred from the MS measurements of m / z alone. − We found evidence for at least seven distributions of HDL particles that were distinct in their mass. These species also differed in electrospray charging properties, as larger particles retain more charge than smaller particles during the final stages of droplet desolvation during transit into the mass spectrometer.…”

Compaction, Relaxation, and Linearization of Megadalton-Sized DNA Plasmids: DNA Structures Probed by CD-MS

“…However, megadalton-sized DNA ions are heterogeneous because of counterions, so peaks due to ions in different charge states are not resolved in the m / z spectrum. Thus, their charge state cannot be determined using conventional MS . Heterogeneous samples can be analyzed by charge detection mass spectrometry (CD-MS), − where the m / z ratio and charge are measured simultaneously for each ion and then multiplied to give the mass.…”