PT  - JOURNAL ARTICLE
AU  - Michael S. Westphall
AU  - Kenneth W. Lee
AU  - Austin Z. Salome
AU  - Jean Lodge
AU  - Timothy Grant
AU  - Joshua J. Coon
TI  - 3D Structure Determination of Protein Complexes using Matrix-Landing Mass Spectrometry
AID  - 10.1101/2021.10.13.464253
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.10.13.464253
4099  - http://biorxiv.org/content/early/2021/10/13/2021.10.13.464253.short
4100  - http://biorxiv.org/content/early/2021/10/13/2021.10.13.464253.full
AB  - Native mass spectrometry (MS) is an emerging technology that can provide complementary data to electron microscopy (EM) for protein structure characterization. Beyond the ability to provide mass measurements of gas-phase biomolecular ions, MS instruments offer the ability to purify, select, and precisely control the spatial location of these ions. Here we present a modified Orbitrap MS system capable of depositing a native MS ion beam onto EM grids. We further describe use of a chemical landing matrix that both preserves and protects the structural integrity of the deposited particles. With this system we obtained the first 3D reconstructed structure of gas-phase, deposited biomolecular ions – the 800 KDa protein complex GroEL. These data provide direct evidence that non-covalent protein complexes can indeed retain their condensed-phase structures following ionization and vaporization. Finally, we describe how further developments of this technology could pave the way to an integrated MS-EM technology with promise to provide improved cryo-EM sample preparation over conventional plunge-freezing techniques.Competing Interest StatementJJC is a consultant for Thermo Fisher Scientific. MSW, AZS, KWL, TG, and JJC are inventors of intellectual property related to these results.