Ion/Ion Reactions of MALDI-Derived Peptide Ions: Increased Sequence Coverage via Covalent and Electrostatic Modification upon Charge Inversion

• Published in: Analytical chemistry (Washington) Vol. 84; no. 24; pp. 10679 - 10685
• Main Authors: Stutzman, John R, McLuckey, Scott A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18-12-2012
• Subjects: Amino Acid Sequence; Analytical chemistry; Atmospheric pressure; Chemistry; Desorption; Electrostatics; Exact sciences and technology; Ions; Mass spectrometry; Molecular Sequence Data; Peptides; Peptides - chemistry; Peptides - genetics; Spectrometric and optical methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Static Electricity; Collisional activation; Peptides; Atmospheric pressure; Disulfonic acid; Inversion; Product; Matrix assisted laser desorption ionization; Dehydration; Schiff base; Arginine; Lysine; Residue; Mass spectrometry MS/MS; Reagents; Cations; Yield; Dissociation; Gas phase; Primary amine; Mass spectrometry; Electrostatic charge
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac302374p

Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI)-derived tryptic peptide ions have been subjected to ion/ion reactions with doubly deprotonated 4-formyl-1,3-benzenedisulfonic acid (FBDSA) in the gas-phase. The ion/ion reaction produces a negatively charged electrostatic complex composed of the peptide cation and reagent dianion, whereupon dehydration of the complex via collision-induced dissociation (CID) produces a Schiff base product anion. Collisional activation of modified lysine-terminated tryptic peptide anions is consistent with a covalent modification of unprotonated primary amines (i.e., N-terminus and ε-NH2 of lysine). Modified arginine-terminated tryptic peptides have shown evidence of a covalent modification at the N-terminus and a noncovalent interaction with the arginine residue. The modified anions yield at least as much sequence information upon CID as the unmodified cations for the small tryptic peptides examined here and more sequence information for the large tryptic peptides. This study represents the first demonstration of gas-phase ion/ion reactions involving MALDI-derived ions. In this case, covalent and electrostatic modification charge inversion is shown to enhance MALDI tandem mass spectrometry of tryptic peptides.