Ammonium Bicarbonate Addition Improves the Detection of Proteins by Desorption Electrospray Ionization Mass Spectrometry

• Published in: Journal of the American Society for Mass Spectrometry Vol. 28; no. 6; pp. 1109 - 1117
• Main Authors: Honarvar, Elahe, Venter, Andre R.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-06-2017; Springer Nature B.V
• Subjects: Analytical Chemistry; Bioinformatics; Biotechnology; Carbonates; Chemistry; Chemistry and Materials Science; Desorption; Electrospraying; Focus - Honoring R. G. Cooks' Election to the National Academy of Sciences: Research Article; Formic acid; Ionization; Ions; Mass spectrometry; Organic Chemistry; Proteins; Proteomics; Scientific imaging; Sensitivity analysis; Signal to noise ratio; Spectroscopy; DESI; Ammonium bicarbonate; Desorption electrospray ionization; Electrospray mechanism; Protein
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1007/s13361-017-1628-9

The analysis of protein by desorption electrospray ionization mass spectrometry (DESI-MS) is considered impractical due to a mass-dependent loss in sensitivity with increase in protein molecular weights. With the addition of ammonium bicarbonate to the DESI-MS analysis the sensitivity towards proteins by DESI was improved. The signal to noise ratio (S/N) improvement for a variety of proteins increased between 2- to 3-fold relative to solvent systems containing formic acid and more than seven times relative to aqueous methanol spray solvents. Three methods for ammonium bicarbonate addition during DESI-MS were investigated. The additive delivered improvements in S/N whether it was mixed with the analyte prior to sample deposition, applied over pre-prepared samples, or simply added to the desorption spray solvent. The improvement correlated well with protein pI but not with protein size. Other ammonium or bicarbonate salts did not produce similar improvements in S/N, nor was this improvement in S/N observed for ESI of the same samples. As was previously described for ESI, DESI also caused extensive protein unfolding upon the addition of ammonium bicarbonate.
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