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Negative ion dissociation of peptides containing hydroxyl side chains
Author(s) -
Pu Dan,
Cassady Carolyn J.
Publication year - 2007
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.3337
Subject(s) - chemistry , side chain , threonine , fourier transform ion cyclotron resonance , dissociation (chemistry) , serine , tandem mass spectrometry , collision induced dissociation , stereochemistry , tyrosine , mass spectrometry , organic chemistry , chromatography , biochemistry , enzyme , polymer
The dissociation of deprotonated peptides containing hydroxyl side chains was studied by electrospray ionization coupled with Fourier transform ion cyclotron resonance (ESI‐FTICR) via sustained off‐resonance irradiation collision induced dissociation (SORI‐CID). Dissociation under post‐source decay (PSD) conditions was performed by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF). This work included hexapeptides with one residue of serine, threonine, or tyrosine and five inert alanine residues. During SORI‐CID and PSD, dissociation of [M–H] − yielded c‐ and y‐ions. Side‐chain losses of formaldehyde (HCHO) from serine‐containing peptides, acetaldehyde (CH 3 CHO) from threonine‐containing peptides, and 4‐methylene‐2,5‐cycohexadienone (C 7 H 6 O) from tyrosine‐containing peptides were generally observed in the negative ion PSD and SORI‐CID spectra. Side‐chain loss occurs much less from tyrosine‐containing peptides than from serine‐ and threonine‐containing peptides. This is probably due to the bulky side chain of tyrosine, resulting in steric hindrance and poor geometry for dissociation reactions. Additionally, a selective cleavage leading to the elimination of the C‐terminal residue from [M–H] − was observed from the peptides with serine and threonine at the C‐terminus. This cleavage does not occur in the dissociation of peptides with an amide group at the C‐terminus or peptides with neutral or basic residues at the C‐terminus. It also does not occur with tyrosine at the C‐terminus. Both the C‐terminal carboxylic acid group and the hydroxyl side chain of the C‐terminal residue must play important roles in the mechanism of C‐terminal residue loss. A mechanism involving both the C‐terminal carboxylic acid group and a hydroxyl side chain of serine and threonine is proposed. Copyright © 2007 John Wiley & Sons, Ltd.