[Applications of chromatography in glycomics].

Glycomics, an emerging "omics" technology that was developed after genomics and proteomics, is a discipline that studies the composition, structure, and functions of glycomes in cells, tissues, and organisms. Glycomics plays key roles in understanding the laws of major life activities, disease prevention and treatment, and drug quality control and development. At present, the structural analysis of glycans relies mainly on mass spectrometry. However, glycans have low abundance in biological samples. In addition, factors such as variable monosaccharide compositions, differences in glycosidic bond positions and modes, diverse branching structures, contribute to the complexity of the compositions and structures of glycans, posing great challenges to glycomics research. Liquid chromatography can effectively remove matrix interferences and enhance glycan separation to improve the mass spectrometric response of glycans. Thus, liquid chromatography and liquid chromatography coupled with mass spectrometry are important technical tools that have been actively applied to solve these problems; these technologies play indispensable roles in glycomics research. Different studies have highlighted similarities and differences in the applications of various types of liquid chromatography, which also reflects the versatility and flexibility of this technology. In this review, we first discuss the enrichment methods for glycans and their applications in glycomics research from the perspective of chromatographic separation mechanisms. We then compare the advantages and disadvantages of these methods. Some glycan-enrichment modes include affinity, hydrophilic interactions, size exclusion, and porous graphitized carbon adsorption. A number of newly developed materials exhibit excellent glycan-enrichment ability. We enumerate the separation mechanisms of reversed-phase high performance liquid chromatography (RP-HPLC), high performance anion-exchange chromatography (HPAEC), hydrophilic interaction chromatography (HILIC), and porous graphitic carbon (PGC) chromatography in the separation and analysis of glycans, and describe the applications of these methods in the separation of glycans, glycoconjugates, and glyco-derivatives. Among these methods, HILIC and PGC chromatography are the most widely used, whereas HPAEC and RP-HPLC are less commonly used. The HILIC and RP-HPLC modes are often used for the separation of derived glycans. The ionization efficiency and detectability of glycans are significantly improved after derivatization. However, the derivatization process is relatively cumbersome, and byproducts inevitably affect the accuracy and completeness of the detection results. HPAEC and PGC chromatography exhibit good separation effects on nonderivative glycans, but issues related to the detection integrity of low-abundance glycans owing to their poor detection effect continue to persist. Therefore, the appropriate analytical method for a specific sample or target analyte or mutual verification must be selected. Finally, we highlight the research progress in various chromatographic methods coupled with mass spectrometry for glycomics analysis. Significant progress has been made in glycomics research in recent years owing to advancements in the development of chromatographic separation techniques. However, several significant challenges remain. As the development of novel separation materials and methods continues, chromatographic techniques may be expected to play a critical role in future glycomics research.

Isolation of Human Milk Difucosyl Nona- and Decasaccharides by Ultrahigh-Temperature Preparative PGC-HPLC and Identification of Novel Difucosylated Heptaose and Octaose Backbones by Negative-Ion ESI-MSn.

Despite their many important physiological functions, past work on the diverse sequences of human milk oligosaccharides (HMOs) has been focused mainly on the highly abundant HMOs with a relatively low degree of polymerization (DP) due to the lack of efficient methods for separation/purification and high-sensitivity sequencing of large-sized HMOs with DP ≥ 10. Here we established an ultrahigh-temperature preparative HPLC based on a porous graphitized carbon column at up to 145 °C to overcome the anomeric α/ß splitting problem and developed further the negative-ion ESI-CID-MS/MS into multistage MSn using a combined product-ion scanning of singly charged molecular ion and doubly charged fragment ion of the branching Gal and adjacent GlcNAc residues. The separation and sequencing method allows efficient separation of a neutral fraction with DP ≥ 10 into 70 components, among which 17 isomeric difucosylated nona- and decasaccharides were further purified and sequenced. As a result, novel branched difucosyl heptaose and octaose backbones were unambiguously identified in addition to the conventional linear and branched octaose backbones. The novel structures of difucosylated DF-novo-heptaose, DF-novo-LNO I, and DF-novo-LNnO I were corroborated by NMR. The various fucose-containing Lewis epitopes identified on different backbones were confirmed by oligosaccharide microarray analysis.

An integrated strategy for the discovery of quality marker of Dactylicapnos scandens based on phytochemical analysis, network pharmacology and activity screening.

Dactylicapnos scandens (D. scandens) is an ethnic medicine commonly used for the treatment of analgesia. In this study, an integrated strategy was proposed for the quality evaluation of D. scandens based on "phytochemistry-network pharmacology-effectiveness-specificity" to discover and determine the quality marker (Q-marker) related to analgesia. First, phytochemical analysis was conducted using UPLC-Q-TOF-MS/MS and a self-built compound library, and 19 components were identified in D. scandens extracts. Next, the "compounds-targets" network was constructed to predict the relevant targets and compounds related to analgesia. Then, the analgesic activity of related compounds was verified through dynamic mass redistribution (DMR) assays on D2 and Mu receptors, and 5 components showed D2 antagonistic activity with IC50 values of 39.2 ± 14.7 µM, 5.46 ± 0.37 µM, 17.5 ± 1.61 µM, 7.89 ± 0.79 µM and 3.29 ± 0.73 µM, respectively. Subsequently, nine ingredients were selected as Q-markers in consideration of specificity, effectiveness and measurability, and their content was measured in 12 batches of D. scandens. Furthermore, the hierarchical cluster analysis and heatmap results indicated that the selected Q-marker could be used to discriminate D. scandens and that the content of Q-marker varied greatly in different batches. Our study shows that this strategy provides a useful method to discover the potential Q-markers of traditional Chinese medicine and offers a practical workflow for exploring the quality consistency of medicinal materials.

Application of chromatography in purification and structural analysis of natural polysaccharides: A review.

Polysaccharides are widely distributed in natural sources from monocytic microorganisms to higher animals, and are found in a variety of biological activities in recent decades. Natural polysaccharides have the characteristics of large molecular weight, diverse composition, and complex structure, so their purification and structural analysis are difficult issues in research. Chromatography as a powerful separation technique, plays an irreplaceable role in the separation and structural analysis of natural polysaccharides, especially in the purification of polysaccharides, the separation of hydrolysates, and the analysis of monosaccharide composition. The separation mechanisms and application of different chromatographic methods in the studies of polysaccharides were summarized in this review. Moreover, the advantages and drawbacks of various chromatography methods were discussed as well.

GIPS-Mix for Accurate Identification of Isomeric Components in Glycan Mixtures Using Intelligent Group-Opting Strategy.

Accurate identification of glycan structures is highly desirable as they are intimately linked to their different functions. However, glycan samples generally exist as mixtures with multiple isomeric structures, making assignment of individual glycan components very challenging, even with the aid of multistage mass spectrometry (MSn). Here, we present an approach, GIPS-mix, for assignment of isomeric glycans within a mixture using an intelligent group-opting strategy. Our approach enumerates all possible combinations (groupings) of candidate glycans and opts in the best-matched glycan group(s) based on the similarity between the simulated spectra of each glycan group and the acquired experimental spectra of the mixture. In the case that a single group could not be elected, a tie break is performed by additional MSn scanning using intelligently selected precursors. With 11 standard mixtures and 6 human milk oligosaccharide fractions, we demonstrate the application of GIPS-mix in assignment of individual glycans in mixtures with high accuracy and efficiency.

Updated clinical and glycomic features of mannosyl-oligosaccharide glucosidase deficiency: Two case reports.

BACKGROUND: Mannosyl-oligosaccharide glucosidase (MOGS) deficiency is an extremely rare type of congenital disorder of glycosylation (CDG), with only 12 reported cases. Its clinical, genetic, and glycomic features are still expanding. Our aim is to update the novel clinical and glycosylation features of 2 previously reported patients with MOGS-CDG. CASE SUMMARY: We collected comprehensive clinical information, and conducted the immunoglobulin G1 glycosylation assay using nano-electrospray ionization source quadruple time-of-flight mass spectrometry. Novel dysmorphic features included an enlarged tongue, forwardly rotated earlobes, a birth mark, overlapped toes, and abnormal fat distribution. Novel imaging findings included pericardial effusion, a deep interarytenoid groove, mild congenital subglottic stenosis, and laryngomalacia. Novel laboratory findings included peripheral leukocytosis with neutrophil predominance, elevated C-reactive protein and creatine kinase, dyslipidemia, coagulopathy, complement 3 and complement 4 deficiencies, decreased proportions of T lymphocytes and natural killer cells, and increased serum interleukin 6. Glycosylation studies showed a significant increase of hypermannosylated glycopeptides (Glc3Man7GlcNAc2/N2H10 and Man5GlcNAc2/N2H5) and hypersialylated glycopeptides. A compensatory glycosylation pathway leading to an increase in Man5GlcNAc2/N2H5 was indicated with the glycosylation profile. CONCLUSION: We confirmed abnormal glycomics in 1 patient, expanding the clinical and glycomic spectrum of MOGS-CDG. We also postulated a compensatory glycosylation pathway, leading to a possible serum biomarker for future diagnosis.

Development of high-throughput UPLC-MS/MS using multiple reaction monitoring for quantitation of complex human milk oligosaccharides and application to large population survey of secretor status and Lewis blood group.

Human milk oligosaccharides (HMOs) have attracted increasing attention due to the emerging evidence of their positive roles for infant's health. A high-throughput method for absolute quantitation of the complex HMOs including multiple isomeric structures is important but very challenging, due to the highly divers nature and wide variation in content of HMOs from different individuals. Here we used UPLC-MS-MRM in the negative-ion mode for accurate quantitation of 23 complex HMOs in just 15 min. The selected oligosaccharides are in their native forms and include neutral and sialylated, fucosylated and non-fucosylated, linear and branched, and secretor and Lewis phenotype indicators. The well validated method with good sensitivity, recovery and reproducibility was then applied to a large population quantitative survey of 251 Chinese mothers from five different ethnic groups (Han, Zhuang, Hui, Mongolian and Tibetan) living in different geographical regions for their secretor's status and Lewis phenotypes.

Calibration for quantitative Fc-glycosylation analysis of therapeutic IgG1-type monoclonal antibodies by using glycopeptide standards.

Fc-glycosylation has crucial impact on the efficacy and safety of IgG-type therapeutic monoclonal antibodies (mAbs). In order to enhance the performance of MS-based bottom-up quantitation strategy, a library of glycopeptide standards containing 26 common IgG1-type Fc-glycoforms has been constructed via modified two-dimensional hydrophilic interaction liquid chromatography (HILIC) purification. Taking advantage of the acquired glycopeptide standards, calibrated quantitation strategy for Fc-glycosylation analysis of mAbs was established and evaluated on the basis of three LC-MS-based methods, including HILIC-MRM (multiple reaction monitoring), HILIC-SIM (selected ion monitor) and RPLC-SIM. Molar concentrations of eleven individual Fc-glycoforms (0.03 ± 0.001-13.77 ± 0.64 nmol mg-1) as well as degree of fucosylation (75.44-97.04%), galactosylation (3.39-49.47%) and mannosylation (1.12-21.22%) in six IgG1-type mAbs were achieved. In addition, Fc-glycosylation site occupancy was also determined from 98.05% to 99.83%. Compared with traditional MS-based quantitation via peak area normalization, the quantitation accuracy and precision of the calibrated strategy had been remarkably improved, especially when combining with HILIC separation. In addition, the transferability of calibrated quantitation as assessed by using MRM-based method had also been significantly enhanced on different instruments from different laboratories. This calibrated quantitation strategy using glycopeptide standards as calibrators will be useful for Fc-glycosylation analysis of IgG1-type mAbs with multiple glycosylation sites.

Purification of natural neutral N-glycans by using two-dimensional hydrophilic interaction liquid chromatography × porous graphitized carbon chromatography for glycan-microarray assay.

Glycan microarray for studying carbohydrate-protein interactions requires diverse classes of well-defined glycan standards. In this study, a purification strategy was established based on two-dimensional hydrophilic interaction liquid chromatography and porous graphitized carbon chromatography (HILIC × PGC) for the acquisition of neutral N-glycan standards from natural source. A total of thirty-one N-glycan compounds including seven pairs of isomers with the amounts from 0.7 to 230.0 nmol were isolated from ovalbumin as the model glycoconjugate. The purified N-glycans covered high-mannose, hybrid as well as multi-antenna asymmetric complex types. The purity of majority of these N-glycans was higher than 90%. Detailed structures of the N-glycan compounds were verified via negative ion tandem MS analysis, in which specific diagnostic ions including D- and E-ions were used to identify isomeric and terminal fine structures. The tag-free glycan compounds with well-defined structures, purity and amounts were finally assembled on the glass slide through neoglycolipid technology. Microarray binding assay of purified glycans with WGA lectin indicated the potential of the established strategy in glycan library expansion and functional glycomics.

Absolute quantitation of high abundant Fc-glycopeptides from human serum IgG-1.

Absolute quantitation of IgG-1 Fc-glycosylation, which is crucial for the clinical practice of glyco-biomarkers and quality control of biopharmaceuticals, has been hindered by the lack of glycopeptide standards. In this study, eleven high abundant IgG-1 Fc-glycopeptides with definite peptide sequences and glycoforms were purified from commercial IgG protein by using two-dimensional hydrophilic interaction liquid chromatographic system. Based on the acquired glycopeptide standards, an absolute quantitation strategy was developed to determine the concentrations of 11 target IgG-1 glycopeptides from pooled human sera. A wide range of Fc-glycopeptide concentrations from 0.60 to 17.61 nmol mL-1 was achieved with excellent accuracy and reproducibility from pooled human sera IgG-1. Compared to conventional relative quantitation, this strategy provides more accurate distribution profiles of 11 high abundant Fc-glycopeptides and degree of glycosylation from pooled human sera IgG-1.