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Formation of deaminated dimer species of amino acids by atmospheric pressure chemical ionization
Author(s) -
Choi SungSeen,
Kim OkBae
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6857
Subject(s) - chemistry , mass spectrometry , ion , chemical ionization , dimer , atmospheric pressure chemical ionization , mass spectrum , molecule , ionization , deuterium , polyatomic ion , analytical chemistry (journal) , inorganic chemistry , chromatography , organic chemistry , quantum mechanics , physics
RATIONALE Interactions of biological molecules to form cluster species play a key role in biological processes and investigation of non‐covalent complexes is one of the research fields using mass spectrometry. Atmospheric pressure chemical ionization mass spectrometry (APCI‐MS) is a useful method for the investigation of cluster formation of amino acids (AAs) by ion‐molecule reactions. METHODS A mixture of 20 protein AAs was ionized by APCI and the product ions were analyzed. The ionization was performed in the positive and negative ion modes. Formation of the homo‐ and heterocluster ions of AAs was investigated. Mechanism for the formation of AA homo‐ and heterocluster ions was examined using hydrogen/deuterium (H/D)‐exchange experiments. RESULTS In the positive ion mode, of the dimer species only the [2Pro + H] + ion was detected. In the negative ion mode, the [2M − H] − ions of His, Val, Ser, and Gln were observed. The deaminated dimers such as the [2Gln − H − NH 3 ] − and [His + Gln − H − NH 3 ] − ions were also observed. In the negative ion mass spectra of the His/Arg, His/Asn, and His/Lys binary mixture solutions, the [His + AA − H − NH 3 ] − ions of Asn, Arg, and Lys were also detected. CONCLUSIONS The number and abundances of the negative product ions were much greater than those of the positive ones. Mechanism for the formation of [2Gln − H − NH 3 ] − and [His + AA − H − NH 3 ] − was examined by deuterium replacement of the amine and hydroxide groups to distinguish the deamination and dehydration reactions with a single quadrupole mass spectrometer. The [His + AA − H − NH 3 ] − ion is formed by ion‐molecule reaction between the [His − H] − ion and a neutral AA. Copyright © 2014 John Wiley & Sons, Ltd.