Imidazole Derivatives Improve Charge Reduction and Stabilization for Native Mass Spectrometry

Noncovalent interactions between biomolecules are critical to their activity. Native mass spectrometry (MS) has enabled characterization of these interactions by preserving noncovalent assemblies for mass analysis, including protein–ligand and protein–protein complexes for a wide range of soluble an...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2019-11, Vol.91 (22), p.14765-14772
Main Authors: Townsend, Julia A, Keener, James E, Miller, Zachary M, Prell, James S, Marty, Michael T
Format: Article
Language:English
Subjects:
Analytical chemistry
Antimicrobial peptides
Biomolecules
Chemical properties
Chemical reduction
Chemistry
Computational chemistry
Computer applications
Coordination compounds
Derivatives
Evaporative cooling
Hydrophobicity
Imidazole
Internal energy
Ionization
Ions
Lipid bilayers
Lipids
Macromolecules
Mass spectrometry
Mass spectroscopy
Membrane proteins
Membranes
Organic chemistry
Peptides
Phase stability
Proteins
Reagents
Scientific imaging
Spectroscopy
Triethylamine
Trimethylamine
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Summary:Noncovalent interactions between biomolecules are critical to their activity. Native mass spectrometry (MS) has enabled characterization of these interactions by preserving noncovalent assemblies for mass analysis, including protein–ligand and protein–protein complexes for a wide range of soluble and membrane proteins. Recent advances in native MS of lipoprotein nanodiscs have also allowed characterization of antimicrobial peptides and membrane proteins embedded in intact lipid bilayers. However, conventional native electrospray ionization (ESI) can disrupt labile interactions. To stabilize macromolecular complexes for native MS, charge reducing reagents can be added to the solution prior to ESI, such as triethylamine, trimethylamine oxide, and imidazole. Lowering the charge acquired during ESI reduces Coulombic repulsion that leads to dissociation, and charge reduction reagents may also lower the internal energy of the ions through evaporative cooling. Here, we tested a range of imidazole derivatives to discover improved charge reducing reagents and to determine how their chemical properties influence charge reduction efficacy. We measured their effects on a soluble protein complex, a membrane protein complex in detergent, and lipoprotein nanodiscs with and without embedded peptides, and used computational chemistry to understand the observed charge-reduction behavior. Together, our data revealed that hydrophobic substituents at the 2 position on imidazole can significantly improve both charge reduction and gas-phase stability over existing reagents. These new imidazole derivatives will be immediately beneficial for a range of native MS applications and provide chemical principles to guide development of novel charge reducing reagents.
ISSN:0003-2700
1520-6882
DOI:10.1021/acs.analchem.9b04263