5 research outputs found
Fragmentation characteristics of glycopeptides
Mass spectrometric analysis of glycopeptides is an emerging strategy for analysis of glycosylation patterns. Here we present an approach using energy resolved collision induced decomposition (CID) spectra to determine structural features of glycopeptides. Fragmentation of multiply protonated glycopeptides proceeds by a series of competing charge separation processes by cleavage of a glycosidic bond, each producing two charged products: a singly charged, âBâ type sugar (oxonium) ion, and a complementary high mass fragment. Energy requirements (activation energies) of these processes are similar to each other, and are far less, than that required for peptide fragmentation. At higher collision energies these first generation products fragment further, yielding a complex fragmentation pattern. Analysis of low energy spectra (those corresponding to ca. 50% survival yield) are straightforward; the ions observed correspond to structural features present in the oligosaccharide, and are not complicated by consecutive reactions. This makes it feasible to identify and distinguish antenna- and core-fucosylated isomers; antenna fucosylation usually suggests presence of the Lewis-X antigen. In general, analysis of the triply protonated molecules are most advantageous, where neutral losses and monosaccharide oxonium ion formation are less abundant
Identification of bifucosylated glycoforms using low energy CID spectra
We have used tandem mass spectrometry based analysis of glycopeptides in order to identify the composition and structure of rare glycoforms. The results illustrate utility of low energy MS/MS for structure identification. We have shown the presence of bi- and tri-fucosylated glycoforms in human alpha-1-acid glycoprotein (AGP), a major plasma glycoprotein. Fucosylation in the case of AGP always occurs on the antennae, core fucosylation was not observed
Investigation of genetic variants of alpha-1 acid glycoprotein by ultra-performance liquid chromatography-mass spectrometry
Genetic variants of human plasma alpha-1 acid glycoprotein (AGP) have been studied in cancer, compared with a group of healthy control. AGP has four genetic variants: AGP F1, F2, and S variants correspond to the ORM1 gene whereas AGP A corresponds to the ORM2 gene. The proportion of ORM1 and ORM2 variants were studied in plasma using a novel UPLCâMS method. Plasma total AGP level was 0.5â±â0.2 g Lâ1 and the proportions of the ORM1 and ORM2 variants were 76.3â±â8.2% and 23.7â±â8.2%, respectively. In cancer plasma AGP levels increased fourfold and the proportion of ORM1 variants increased to 88.7â±â6.8%. Changes in the proportion of genetic variants due to cancer were clearly significant, as shown by statistical analysis. Three different cancer types have been studied, lymphoma, melanoma, and ovarian cancer. The results did not show any difference depending on cancer type. The results indicate that, in accordance with prior expectations, the ORM1 variant is predominantly responsible for the acute-phase property of AGP