Abstract
We present new tags based on the derivatives of phenylboronic acid and apply them for the selective detection of sugars and peptide-sugar conjugates in mass spectrometry. We investigated the binding of phenylboronic acid and its quaternary ammonium salt (QAS) derivatives to carbohydrates and peptide-derived Amadori products by HR-MS and MS/MS experiments. The formation of complexes between sugar or sugar-peptide conjugates and synthetic tags was confirmed on the basis of the unique isotopic distribution resulting from the presence of boron atom. Moreover, incorporation of a quaternary ammonium salt dramatically improved the efficiency of ionization in mass spectrometry. It was found that the formation of a complex with phenylboronic acid stabilizes the sugar moiety in glycated peptides, resulting in simplification of the fragmentation pattern of peptide-derived Amadori products. The obtained results suggest that derivatization of phenylboronic acid as QAS is a promising method for sensitive ESI-MS detection of carbohydrates and their conjugates formed by non-enzymatic glycation or glycosylation. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s13361-014-0857-4) contains supplementary material, which is available to authorized users.
Highlights
Glycation, one of the post-translational modifications of proteins, is a nonenzymatic reaction between sugar aldehyde or ketone and the amino groups of proteins
We designed and synthesized new tags based on the combination of phenylboronic acid and quaternary ammonium salt and used them for selective detection of sugars and sugar-peptide conjugates, taking into account that incorporation of QAS into peptide chain significantly improves the efficiency of ionization of these compounds by mass spectrometry [35]
The mixture of Fmoc-Lys(Fru)-OH and phenylboronic acid was incubated in ammonium carbonate buffer at the pH 9.0
Summary
One of the post-translational modifications of proteins, is a nonenzymatic reaction between sugar aldehyde or ketone and the amino groups of proteins. M. Kijewska et al.: Phenylboronic QAS Tags for Carbohydrates low concentration of modified proteins and peptides, new methods of selective detection based on isotopic labeling (13C or 18O) combined with mass spectrometry were researched [10, 11]. In case of LC-MS analysis of glycated peptides, borate affinity columns based on the specific interaction between phenylboronic acid derivatives and diols in sugar moieties have been used [12, 13].
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