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Arginine‐mimic labeling with guanidinoethanethiol to increase mass sensitivity of lysine‐terminated phosphopeptides by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Author(s) -
Ahn Yeong Hee,
Ji Eun Sun,
Lee Ji Yeon,
Cho Kun,
Yoo Jong Shin
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.3085
Subject(s) - chemistry , guanidine , lysine , matrix assisted laser desorption/ionization , mass spectrometry , arginine , chromatography , peptide , desorption , phosphopeptide , protonation , matrix (chemical analysis) , amino acid , biochemistry , ion , organic chemistry , adsorption
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) generally shows better mass sensitivity for arginine‐terminated peptides than for lysine‐terminated peptides, presumed to arise from the higher proton affinity of the guanidine group in arginine. Here, we report a new method for analyzing phosphopeptides in which phosphopeptides are labeled with a novel chemical tag, guanidinoethanethiol (GET), by a β ‐elimination/Michael addition before MS analysis. GET labeling converts phosphoserine into guanidinoethylcysteine (Gec) containing a guanidine moiety, along with an increase in mass of 21.1 Da. GET‐labeled peptides are detected by MALDI MS with greatly increased peak intensities compared to those of intact phosphopeptides. In particular, GET labeling of lysine‐terminated phosphopeptides dramatically increased peak intensity. GET labeling of lysine‐terminated phosphopeptides improved sensitivity up to 22 times compared to that of the corresponding aminoethanethiol (AET) labeling, in which AET was used as a labeling tag containing an amino group instead of the guanidine group. These results show the guanidine group plays a very important role in increasing the observed sensitivity of MALDI MS for labeled peptide, derivatized from serine‐phosphorylated peptides. Copyright © 2007 John Wiley & Sons, Ltd.