Correlation between Sweet Spots of Glycopeptides and Polymorphism of the Matrix Crystal in MALDI Samples

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 di erences 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 speci c crystal form of 2,5-DHBA could be made. e 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. e results suggest that the introduction of a hydrophobic/aromatic moiety to glycopeptides results in a more successful MALDI analysis due to the e ective incorporation of the analyte into matrix crystals.

Amorphous Conjugated Polymers as Efficient Dual‐Mode MALDI Matrices for Low‐Molecular‐Weight Analytes

“…Crystal formation and analyte incorporation are influenced by the sample preparation method and several method related parameters; e. g. it was reported that the commonly used air‐dried‐droplet method leads to poor homogeneity, while electrospray sample preparation gives evenly sized matrix crystals with well‐distributed analyte incorporation . Furthermore, a low vapor pressure of the used solvent and a longer drying time improves the crystal formation and promotes homogeneous incorporation of the analyte . However, the formation of crystal layers with a homogeneous analyte distribution is difficult to achieve when using SOMs, often resulting in analyte‐rich “hotspots” and analyte‐poor areas …”

Salt Tolerance Enhancement of Liquid Chromatography-Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Using Matrix Additive Methylenediphosphonic Acid

“…DHB is a "cool" matrix. It can reduce undesired fragmentation of fragile analytes and is useful for measuring glycopeptides 19) and phosphopeptides. 17) e following sections discuss the e ects of matrix additives on the DHB.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2011–2012

“…Nishikaze et al (2012a) have investigated the crystals formed by the matrix using Raman spectrometry and found that they exist as two polymorphs. Using peptides and glycopeptides, the investigators found that the peptides were distributed in both types of crystals, whereas the glycopeptides distributed mainly to the Raman spectrum B, which is generated at the early stages of crystallization.…”