Transforming the potential of mass spectrometry

Advances in mass spectrometry (MS) technology over the last half a century have transformed the way scientists understand the structure and behaviour of molecules. However, the masses of many biomolecules and materials, such as protein complexes, intact viruses, and polymers, are too large for characterisation by traditional MS.

Charge detection mass spectrometry (CDMS) can resolve the charge states of macromolecules with masses greater than 10 megadaltons (MDa), where current gold standard methods such as electrospray ionisation (ESI) struggle to achieve sufficient mass-to-charge ratio (m/z) resolution. Through its ability to detect both the m/z and charge of single ions, CDMS technology measures the true mass of individual particles and opens the door to a variety of applications that were previously out of reach.

As the first commercial CDMS instrument on the market, the TrueMass system has turned the mass analysis of ultra-high molecular weight particles into a reality. Until now, the applications of CDMS technology have been limited due to the trade-off between resolution and throughput. The next-generation mass analyser geometry and advanced electronics speed up ion trap CDMS, making this technology widely accessible for a range of research and industrial applications.



Intact virus analysis

MS is an invaluable tool for examining the structure and function of viruses and has long been used to identify viral capsid proteins, detect mutations, and characterize post-translational modifications (PTMs). Intact virus analysis has been made possible in recent years by advances in CDMS technology, not only overcoming the previous particle size limit of ESI-MS but allowing the in-depth characterisation of viral glycoprotein heterogeneity.

These developments are driving vital steps forward in our understanding of SARS-CoV-2 – the virus behind the COVID-19 pandemic. Considerable attention has been paid to the virus’ spike (S) protein, a large trimeric transmembrane protein that facilitates entry into host cells and is involved in neutralizing antibody and T-cell responses. CDMS allows researchers to measure the intact mass of the S protein and to capture the dynamic range of glycans present, with the goal of leading to the development of more targeted therapeutics.¹

The creation of vaccines that use a viral vector for delivery is another field benefiting from the high resolving power of CDMS technology. Scientists can identify whether viral RNA/DNA has been successfully inserted into the vector capsids, by using the exact charge to identify less dense hollow

shells from more compact structures.²

Polymer research

Synthetic polymers, used for a vast range of commercial and industrial applications, exist in a broad spectrum of shapes and molecular weights, making them difficult to characterize. Analytical techniques such as nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy and, more recently, MS, are widely used in polymer research, but the development of increasingly large and complex polymeric materials confounds mass determination due to overlapping charge distributions.

CDMS technology is an ideal technique that provides a direct measurement of the mass distribution of large polymeric materials, and has been successfully used to determine the mass of poly(ethylene oxides) – PEOs – in the MDa mass range.^3,4

^

Atmospheric aerosol detection

Characterizing airborne particles is vital for a number of applications, from pollution analysis to minimising respiratory hazards for astronauts. CDMS can be coupled with separation techniques that enable single particle analysis of atmospheric aerosols, and the resulting quantitative information could help inform regulations to control the quality of ambient air.



References:

1.     Miller LM et al. Heterogeneity of Glycan Processing on Trimeric SARS-CoV‑2 Spike Protein Revealed by Charge Detection Mass Spectrometry, J. Am. Chem. Soc. 2021, 143, 3959−3966.

2.     Keifer DZ et al. Acquiring Structural Information on Virus Particles with Charge Detection Mass Spectrometry, J. Am. Soc. Mass Spectrom. (2016) 27:1028-1036.

3.     Doussineau T. et al. Charging megadalton poly(ethylene oxide)s by electrospray ionization. A charge detection mass spectrometry study. Rapid Commun. Mass Spectrom. 2011, 25, 617–623.

4.     Antoine R. Weighing synthetic polymers of ultra‐high molar mass and polymeric nanomaterials: What can we learn from charge detection mass spectrometry? Rapid Commun Mass Spectrom. 2020;e8539.