Native Mass Spectrometry of Soluble Proteins with Sodium Chloride Enabled by a Dendritic Detergent

Abstract

Salts are essential for maintaining native protein structure and biomolecular interactions. Native mass spectrometry often yields uninterpretable spectra due to salt adduction and signal suppression. Existing workarounds require buffer exchange or extensive cleanup, which can disrupt weak noncovalent interactions and reduce throughput. Addressing this shortcoming, we establish a first-generation, dendritic triglycerol detergent as a simple-to-apply additive that enables native mass spectrometry of biophysically relevant protein concentrations in the presence of sodium chloride. Adding this detergent to sodium chloride–containing samples prior to electrospray ionization improves spectral quality, enhances signal-to-noise ratios, and enables an acquisition of interpretable native mass spectrometry data for soluble proteins, including complexes with lipids and drugs, at different ionic strengths. These improvements are achieved without compromising native-like charge-state distributions across proteins ranging from myoglobin and lipopolysaccharide transport protein H to bovine serum albumin and high-mass tetramers, such as alcohol dehydrogenase and pyruvate kinase. Nuclear magnetic resonance data indicate a concentration-dependent sodium chloride complexation by detergent in solution, consistent with desalted protein complexes observable in the gas phase. By rendering sodium chloride compatible with native mass spectrometry, first-generation, dendritic triglycerol detergent enables the routine analysis of protein complexes at otherwise inaccessible ionic strengths and biophysically relevant analyte concentrations.