Use of a novel ionic liquid matrix for MALDI‐MS analysis of glycopeptides and glycans out of total tryptic digests

Abstract

In this study, we investigated a novel ionic liquid matrix (ILM), namely, the 1,1,3,3-tetramethylguanidinium salt of 2,4,6-trihydroxyacetophenone (THAP). This matrix[1,1,3,3-tetramethylguanidinium 2,4,6-trihydroxyacetophenone (GTHAP)] turned out to be well suited for the matrix-assisted laser desorption/ionization mass spectrometric analysis of glycopeptides and glycans, and overcame the well-known ionization suppression of carbohydrate structures in the presence of peptides. The matrix was evaluated by two different series of experiments, in each case in comparison with the crystalline THAP matrix. In the first set of experiments, mass spectra were taken from unseparated tryptic digests of three glycoproteins taken as model compounds. Even glycopeptides containing short peptide backbones and large carbohydrate moieties gave high signal intensities when using the ILM though they did not appear in the THAP spectra. In the second set of experiments, the total tryptic digests were treated with endoglycosidase PNGase F to cleave off the N-linked glycans. When using the GTHAP matrix, it was possible to detect the glycans with high intensities in the presence of the tryptic peptides, whereas glycan ionization was completely suppressed when measured with the solid matrix THAP. The extent of metastable decay of glycopeptides was reduced when using the ILM. Altogether, GTHAP proved as a useful ILM particularly being superior to solid matrices in the context of glycosylation analysis.

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2009–2010

“…When using the liquid matrix, it was possible to detect the glycans with high intensities in the presence of the tryptic peptides, whereas, once again, glycan ionization was completely suppressed when measured with THAP alone. The extent of metastable decay of glycopeptides was also found to be reduced when using the liquid matrix (Ullmer & Rizzi, 2009). Ionic liquid matrices have shown considerable advantages over conventional matrices for MALDI-MS analysis of polysulfated carbohydrates such as heparin and heparin sulfate.…”

Novel Ionic Matrices for Enhanced Ionization of Oligosaccharides/Glycopeptides during MALDI-MS Analysis

“…[16,17] , 这类方法在诸多领域都表现出了极好的应用 前景 [18～20] . 已有报道指出, 三羟基苯乙酮(THAP)作为 基质使用时, 能显著提高寡糖 [21] 、磷脂 [22] 及核酸分子 [23] 在 MALDI-MS 分析中的灵敏度, 而当 2′,4′,6′-三羟基苯 乙酮与 1,1,3,3-四甲基胍形成离子液体用于糖肽及寡糖 链的质谱分析时 [24] , 与使用单一的 THAP 基质相比, 能 使肽链骨架较短的糖肽也实现高效离子化, 从而鉴定到 更多糖肽, 但与此同时, 该离子液体也引入了更多的杂 峰导致谱图更为复杂. 此外, 目前尚无采用 2′,3′,4′-三羟 2 结果与讨论 3 .…”

Hydrazinonicotinic acid derivatization for selective ionization and improved glycan structure characterization by MALDI-MS

“…[7][8][9] Nevertheless, the analysis of glycans by MALDI-MS may still run into a bottleneck, which generally stems from their inherent low abundance and low ionization efficiency. 17 Later, a new matrix such as the ionic liquid matrix (ILM) 18 and diamond nanoparticles 19 were reported to selectively improve the ionization of glycans and glycopeptides, enabling the selective detection of glycans in complex peptide-glycan mixtures. To facilitate direct and effective mass spectrometry measurements of glycans from mixtures, selectively improving the ionization efficiency of glycans is particularly fascinating and urgently required.…”