Acute-phase glycoprotein N-glycome of ovarian cancer patients analyzed by CE-LIF.

Epithelial ovarian cancer (EOC) is the most frequent cause of death from all gynecological malignancies because of its late diagnosis. As N-glycosylation is modified in the course of ovarian cancer, it is a promising source of tumor biomarkers. In this work, serum glycoproteins, depleted from albumin and IgG, were separated by 2DE. Protein spots of acute-phase proteins were identified by peptide mapping and their corresponding glycan moieties were released enzymatically, fluorescently labeled and analyzed by CE-LIF. In the positive acute-phase proteins, haptoglobin, α1-antitrypsin, and α1-antichymotrypsin, an increase of antennarity and Lewis(X) motif could be measured in EOC patients on tri- and/or tetraantennary N-glycans. Tetraantennary N-glycans containing three Lewis(X) epitopes and triantennary N-glycans containing a ß(1-6) branch and a Lewis(X) epitope were only present in EOC patients. We also showed for the first time that the core-fucosylated biantennary digalactosylated N-glycan of α1-acid glycoprotein is a potential biomarker for EOC. To conclude, core-fucosylated biantennary N-glycans on α1-acid glycoprotein as well as higher antennarity and increased amounts of Lewis(X) motif on haptoglobin, α1-antitrypsin, and α1-antichymotrypsin are promising biomarkers for EOC. Nevertheless, their specificity and selectivity for the early detection of EOC should be evaluated in a larger study.

Automated solid-phase extraction coupled online with HPLC-FLD for the quantification of zearalenone in edible oil.

Established maximum levels for the mycotoxin zearalenone (ZEN) in edible oil require monitoring by reliable analytical methods. Therefore, an automated SPE-HPLC online system based on dynamic covalent hydrazine chemistry has been developed. The SPE step comprises a reversible hydrazone formation by ZEN and a hydrazine moiety covalently attached to a solid phase. Seven hydrazine materials with different properties regarding the resin backbone, pore size, particle size, specific surface area, and loading have been evaluated. As a result, a hydrazine-functionalized silica gel was chosen. The final automated online method was validated and applied to the analysis of three maize germ oil samples including a provisionally certified reference material. Important performance criteria for the recovery (70-120 %) and precision (RSDr <25 %) as set by the Commission Regulation EC 401/2006 were fulfilled: The mean recovery was 78 % and RSDr did not exceed 8 %. The results of the SPE-HPLC online method were further compared to results obtained by liquid-liquid extraction with stable isotope dilution analysis LC-MS/MS and found to be in good agreement. The developed SPE-HPLC online system with fluorescence detection allows a reliable, accurate, and sensitive quantification (limit of quantification, 30 µg/kg) of ZEN in edible oils while significantly reducing the workload. To our knowledge, this is the first report on an automated SPE-HPLC method based on a covalent SPE approach.

Enhanced detection of in-gel released N-glycans by MALDI-TOF-MS.

Many biologically relevant glycoproteins need to be separated on 1D- or 2D-gels prior to analysis and are available in picomole amounts. Therefore, it is important to have optimized methods to unravel the glycome that combine in-gel digestions with MALDI-TOF-MS. In this technical report, we investigated how the detection of in-gel released N-glycans could be improved by MALDI-TOF-MS. First, an AnchorChip target was tested and compared to ground steel target using several reference oligosaccharides. The highest signals were obtained with an AnchorChip target and D-arabinosazone as the matrix; a LOD of 1.3 to 10 fmol was attained. Then, the effect of octyl-ß-glucopyranoside, a nonionic detergent, was studied during in-gel peptide-N(4) -(acetyl-ß-glucosaminyl) asparagine amidase F digestion of standard glycoproteins and during glycan extraction. Octyl-ß-glucopyranoside increased the intensity and the amount of detected neutral as well as acidic N-glycans. A LOD of under 7 pmol glycoprotein could be achieved.

Identification of 34 N-glycan isomers in human serum by capillary electrophoresis coupled with laser-induced fluorescence allows improving glycan biomarker discovery.

Alterations in glycosylation have been observed in many human diseases and specific changes in glycosylation have been proposed as relevant diagnostic information. Capillary electrophoresis coupled with laser-induced fluorescence (CE-LIF) is a robust method to quantify desialylated N-glycans that are labeled with 8-aminopyrene-1,3,6-trisulfonic acid prior to analysis. To date, only a maximum of 12 glycan structures, the most abundant ones, have been identified by CE-LIF to characterize glycome modulations of total serum in the course of the diseases. In most forms of cancer, findings using CE-LIF were limited to the increase of triantennary structures carrying a Lewis(x) epitope. In this work, we identified 32 linkage and positional glycan isomers in healthy human serum using exoglycosidase digestions as well as standard glycoproteins, for which we report the assignment of novel structures. It was possible to identify and quantify 34 glycan isomers in the serum of primary epithelial ovarian cancer patients (EOC). Reduced levels of diantennary structures and of high-mannose 5 were statistically significant in the EOC samples, and also, elevated branching as well as increased antennary fucosylation were observed. For the first time, we could demonstrate that not only antennary fucosylation was of relevance in tetraantennary structures but also core-fucosylated tetraantennary N-glycans were statistically increased in EOC patients. The results of the current study provide an improved dataset to be used in glycan biomarker discovery.