Mass Spectrometry
Online ISSN : 2186-5116
Print ISSN : 2187-137X
ISSN-L : 2186-5116
Original Article
Correlation between Sweet Spots of Glycopeptides and Polymorphism of the Matrix Crystal in MALDI Samples
Takashi NishikazeHisako OkumuraHiroshi JinmeiJunko Amano
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JOURNALS FREE ACCESS

2012 Volume 1 Issue 1 Pages A0006-

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Abstract

A standard dried-droplet preparation using 2,5-dihydroxybenzoic acid (2,5-DHBA) as the matrix results in a large variation in signal intensity and poor shot-to-shot reproducibility in matrix-assisted laser desorption/ionization (MALDI). We expected that the differences can be attributed to the nature of the crystal structures in the region of the “sweet spot” within the MALDI samples. 2,5-DHBA crystals with and without analytes on a target plate obtained by means of a dried-droplet preparation contain two polymorphs, which can be distinguished by Raman spectra. In comparing the Raman image with the MS image, a clear correlation between the signal distribution of glycopeptides and hydrophilic peptides and the specific crystal form of 2,5-DHBA could be made. The ionization of hydrophobic peptides appears to proceed in both types of polymorphic crystals. In addition, the derivatization of glycopeptides with a pyrene group enabled us to detect glycopeptides regardless the crystal form. As the result, the number of sweet spots increased and MS spectra with a high signal intensity were obtained. The results suggest that the introduction of a hydrophobic/aromatic moiety to glycopeptides results in a more successful MALDI analysis due to the effective incorporation of the analyte into matrix crystals.

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© 2012 The Mass Spectrometry Society of Japan
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