A systematic approach to protein glycosylation analysis: a path through the maze

Immunoglobulin G glycosylation and its alterations in aging-related diseases

Immunoglobulin G (IgG) is an important serum glycoprotein and a major component of antibodies. Glycans on IgG affect the binding of IgG to the Fc receptor or complement C1q, which in turn affects the biological activity and biological function of IgG. Altered glycosylation patterns on IgG emerge as important biomarkers in the aging process and age-related diseases. Key aging-related alterations observed in IgG glycosylation include reductions in galactosylation and sialylation, alongside increases in agalactosylation, and bisecting GlcNAc. Understanding the role of IgG glycosylation in aging-related diseases offers insights into disease mechanisms and provides opportunities for the development of diagnostic and therapeutic strategies. This review summarizes five aspects of IgG: an overview of IgG, IgG glycosylation, IgG glycosylation with inflammation mediation, IgG glycan changes with normal aging, as well as the relevance of IgG glycan changes to aging-related diseases. This review provides a reference for further investigation of the regulatory mechanisms of IgG glycosylation in aging-related diseases, as well as for evaluating the potential of IgG glycosylation changes as markers of aging and aging-related diseases.

Direct Glycan Analysis of Biological Samples and Intact Glycoproteins by Integrating Machine Learning-Driven Surface-Enhanced Raman Scattering and Boronic Acid Arrays

Frequent monitoring of glycan patterns is a critical step in studying glycan-mediated cellular processes. However, the current glycan analysis tools are resource-intensive and less suitable for routine use in standard laboratories. We developed a novel glycan detection platform by integrating surface-enhanced Raman spectroscopy (SERS), boronic acid (BA) receptors, and machine learning tools. This sensor monitors the molecular fingerprint spectra of BA binding to cis-diol-containing glycans. Different types of BA receptors could yield different stereoselective reactions toward different glycans and exhibit unique vibrational spectra. By integration of the Raman spectra collected from different BA receptors, the structural information can be enriched, eventually improving the accuracy of glycan classification and quantification. Here, we established a SERS-based sensor incorporating multiple different BA receptors. This sensing platform could directly analyze the biological samples, including whole milk and intact glycoproteins (fetuin and asialofetuin), without tedious glycan release and purification steps. The results demonstrate the platform's ability to classify milk oligosaccharides with remarkable classification accuracy, despite the presence of other non-glycan constituents in the background. This sensor could also directly quantify sialylation levels of a fetuin/asialofetuin mixture without glycan release procedures. Moreover, by selecting appropriate BA receptors, the sensor exhibits an excellent performance of differentiating between α2,3 and α2,6 linkages of sialic acids. This low-cost, rapid, and highly accessible sensor will provide the scientific community with an invaluable tool for routine glycan screening in standard laboratories.

Protein Haptenation and Its Role in Allergy

Humans are exposed to numerous electrophilic chemicals either as medicines, in the workplace, in nature, or through use of many common cosmetic and household products. Covalent modification of human proteins by such chemicals, or protein haptenation, is a common occurrence in cells and may result in generation of antigenic species, leading to development of hypersensitivity reactions. Ranging in severity of symptoms from local cutaneous reactions and rhinitis to potentially life-threatening anaphylaxis and severe hypersensitivity reactions such as Stephen-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), all these reactions have the same Molecular Initiating Event (MIE), i.e. haptenation. However, not all individuals who are exposed to electrophilic chemicals develop symptoms of hypersensitivity. In the present review, we examine common chemistry behind the haptenation reactions leading to formation of neoantigens. We explore simple reactions involving single molecule additions to a nucleophilic side chain of proteins and complex reactions involving multiple electrophilic centers on a single molecule or involving more than one electrophilic molecule as well as the generation of reactive molecules from the interaction with cellular detoxification mechanisms. Besides generation of antigenic species and enabling activation of the immune system, we explore additional events which result directly from the presence of electrophilic chemicals in cells, including activation of key defense mechanisms and immediate consequences of those reactions, and explore their potential effects. We discuss the factors that work in concert with haptenation leading to the development of hypersensitivity reactions and those that may act to prevent it from developing. We also review the potential harnessing of the specificity of haptenation in the design of potent covalent therapeutic inhibitors.

The Impact of Protein Glycosylation on the Identification of Patients with Pediatric Appendicitis

The identification of pediatric appendicitis is challenging due to the lack of specific markers thereby several factors are included in the diagnostic process such as abdominal pain, ultrasonography and altered laboratory parameters (C reactive protein, absolute neutrophil cell number and white blood cell number). The glycosylation pattern of serum N-glycome was analyzed in this study of 38 controls and 40 patients with pediatric appendicitis. The glycans were released by enzymatic deglycosylation followed by fluorescent labeling and solid-phase extraction. The prepared samples were analyzed by hydrophilic interaction liquid chromatography with fluorescence and mass-spectrometric detection. The generated data were analyzed by multiple statistical tests involving the most important laboratory parameters as well. Significant differences associated with the examined patient groups were revealed suggesting the potential use of glycosylation analysis supporting the detection of pediatric appendicitis.

Machine learning tool as an enabler for rapid quantification of monoclonal antibodies N-glycans using fluorescence detector

Liquid chromatography-mass spectrometry (LC-MS) is widely used for identification and quantification of N-glycans of monoclonal antibodies (mAbs), owing to its high sensitivity and accuracy. However, its resource-intensive nature necessitates the development of rapid and cost-effective orthogonal analysis approaches. This study aims to develop an online method utilizing the Extreme Gradient Boosting (XGBoost) machine learning (ML) algorithm for real time quantification of InstantPC labelled N-glycans by Liquid Chromatography (LC) - fluorescence detector (FLD). The LC-FLD profile is pre-processed for baseline correction and noise reduction prior to fed to the machine learning (ML) algorithm. The algorithm has been successfully tested for commercial and inhouse developed mAbs and validated using LC-MS quantification as reference. The LC-FLD-ML model predicted values were at par with the LC-MS values with root mean square error of <0.5 and R2 of >0.95. The average errors using ML model (1.80 %) was reduced by a minimum of 28 % and 40 % for origin (1.5 %) and manual (1.07 %) based integration, respectively. The approach reduces the data analysis time per sample by ~70 % (from ~5 min to ~1.5 min), thereby offering a time and resource efficient orthogonality with LC-MS for quantification of N-glycans in mAbs.

What is the role of current mass spectrometry in pharmaceutical analysis?

The role of mass spectrometry (MS) has become more important in most application domains in recent years. Pharmaceutical analysis is specific due to its stringent regulation procedures, the need for good laboratory/manufacturing practices, and a large number of routine quality control analyses to be carried out. The role of MS is, therefore, very different throughout the whole drug development cycle. While it dominates within the drug discovery and development phase, in routine quality control, the role of MS is minor and indispensable only for selected applications. Moreover, its role is very different in the case of analysis of small molecule pharmaceuticals and biopharmaceuticals. Our review explains the role of current MS in the analysis of both small-molecule chemical drugs and biopharmaceuticals. Important features of MS-based technologies being implemented, method requirements, and related challenges are discussed. The differences in analytical procedures for small molecule pharmaceuticals and biopharmaceuticals are pointed out. While a single method or a small set of methods is usually sufficient for quality control in the case of small molecule pharmaceuticals and MS is often not indispensable, a large panel of methods including extensive use of MS must be used for quality control of biopharmaceuticals. Finally, expected development and future trends are outlined.

Global O-glycoproteome enrichment and analysis enabled by a combinatorial enzymatic workflow

A comprehensive analysis of site-specific protein O-glycosylation is hindered by the absence of a consensus O-glycosylation motif, the diversity of O-glycan structures, and the lack of a universal enzyme that cleaves attached O-glycans. Here, we report the development of a robust O-glycoproteomic workflow for analyzing complex biological samples by combining four different strategies: removal of N-glycans, complementary digestion using O-glycoprotease (IMPa) with/without another protease, glycopeptide enrichment, and mass spectrometry with fragmentation of glycopeptides using stepped collision energy. Using this workflow, we cataloged 474 O-glycopeptides on 189 O-glycosites derived from 79 O-glycoproteins from human plasma. These data revealed O-glycosylation of several abundant proteins that have not been previously reported. Because many of the proteins that contained unannotated O-glycosylation sites have been extensively studied, we wished to confirm glycosylation at these sites in a targeted fashion. Thus, we analyzed selected purified proteins (kininogen-1, fetuin-A, fibrinogen, apolipoprotein E, and plasminogen) in independent experiments and validated the previously unknown O-glycosites.

Exposing the molecular heterogeneity of glycosylated biotherapeutics

The heterogeneity inherent in today's biotherapeutics, especially as a result of heavy glycosylation, can affect a molecule's safety and efficacy. Characterizing this heterogeneity is crucial for drug development and quality assessment, but existing methods are limited in their ability to analyze intact glycoproteins or other heterogeneous biotherapeutics. Here, we present an approach to the molecular assessment of biotherapeutics that uses proton-transfer charge-reduction with gas-phase fractionation to analyze intact heterogeneous and/or glycosylated proteins by mass spectrometry. The method provides a detailed landscape of the intact molecular weights present in biotherapeutic protein preparations in a single experiment. For glycoproteins in particular, the method may offer insights into glycan composition when coupled with a suitable bioinformatic strategy. We tested the approach on various biotherapeutic molecules, including Fc-fusion, VHH-fusion, and peptide-bound MHC class II complexes to demonstrate efficacy in measuring the proteoform-level diversity of biotherapeutics. Notably, we inferred the glycoform distribution for hundreds of molecular weights for the eight-times glycosylated fusion drug IL22-Fc, enabling correlations between glycoform sub-populations and the drug's pharmacological properties. Our method is broadly applicable and provides a powerful tool to assess the molecular heterogeneity of emerging biotherapeutics.

Updates of the current strategies of labeling for N-glycan analysis

This mini review summarizes the current methods used for screening N-glycosylation of glycoproteins, with a specific focus on therapeutic proteins and on techniques involving the release of N-glycans. With the continuous development of biopharmaceuticals, particularly monoclonal antibodies (mAbs), which are N-glycosylated proteins, monitoring has gained importance in recent decades. Glycosylation of therapeutic glycoproteins is considered a critical quality attribute because it can impact the efficacy and safety of these therapeutic drugs. The protocols and instrumentation have evolved with the advancement of technologies. Nowadays, methods are becoming increasingly robust, rapid, and sensitive. For the release of N-glycans, the most commonly used method is enzymatic release using PNGase F. The latter is discussed in light of the advent of rapid release that is now possible. The strategy for separating N-glycans using either liquid chromatography (LC) with hydrophilic interaction liquid chromatography (HILIC) chemistry or capillary electrophoresis will be discussed. The selection of the labeling agent is a crucial step in sample preparation for the analysis of released N-glycans. This review also discusses labeling agents that are compatible with and dependent on the separation and detection techniques employed. The emergence of multiplex labeling agents is also summarized. The latter enables the analysis of multiple samples in a single run, but it requires MS analysis.

Triplex glycan quantification by metabolic labeling with isotopically labeled glucose in yeast

Mass spectrometry-based approaches encompass a powerful collection of tools for the analysis biological molecules, including glycans and glycoconjugates. Unlike most traditional bioanalytical methods focusing on these molecules, mass spectrometry is especially suited for multiplexing, by utilizing stable-isotope labeling. Indeed, stable isotope-based multiplexing can be regarded as the gold-standard approach in reducing noise and uncertainty in quantitative mass spectrometry and quantitative analyses generally. The increasing sophistication and depth of biological questions being asked continue to challenge the practitioners of mass spectrometry method development. To understand the biological relevance of glycans, many stable isotope labeling-based mass spectrometry methods have been developed. Based on the duplex MILPIG (metabolic isotope labeling of polysaccharides with isotopic glucose), we establish here a novel triplex isotope labeling method using baker's yeast as the model system. Two differentially isotope-labeled glucoses (medium: 1-13C1 and heavy: 1,2-13C2), in addition to natural abundance glucose (light), were successfully used to label each monosaccharide ring in N-linked glycans in three different cell culture conditions, that, after sample mixing, resulted in a predictable triplet spectrum amenable for relative quantitation. We demonstrate excellent accuracy and precision of relative quantitation for a 1:1:1 mixture of glycans labeled in such a fashion. In addition, we applied triplex MILPIG to interrogate differential N-glycan profiles in tunicamycin-treated and control yeast cells and show that different N-glycans respond differently to tunicamycin.

Oriented assembly of hydrophilic nanochains modified by porous zirconium-based coordination polymers for glycopeptides analysis

Mass spectrometry (MS)-based glycoproteomics research requires additional sample pretreatment to improve the effective identification of low-abundance glycopeptides without interference from non-glycoproteins. Herein, an attractive strategy using resorcinol-formaldehyde (RF) resin and zirconium-based coordination polymer (Zr-BCP) was established to prepare one-dimensional porous coordination polymer composites for glycopeptide enrichment before MS analysis. The obtained Fe3O4@RF@Zr-BCP nanochains feature excellent magnetic response (42.26 emu/g), high hydrophilicity (16.0°), and large specific surface area (140.84 m2/g), which provides abundant affinity sites for specific capture of glycopeptides. The materials exhibit outstanding performance in the enrichment of glycopeptides in terms of sensitivity (15 fmol/μL IgG), selectivity (1:200, molar ratio of IgG/BSA), loading capacity (200 mg/g) and recovery (106.4 ± 3.5%). In addition, the developed method based on Fe3O4@RF@Zr-BCP has been successfully applied to capture glycopeptides in tryptic digest of mouse teratoma cell extracts. It is worth emphasizing that compared with dispersed nanoparticles, the one-dimensional chain structure brings extraordinary reusability to Fe3O4@RF@Zr-BCP nanochains, which is conducive to the rapid cyclic enrichment of glycopeptides. This present work provides a potential enrichment platform for comprehensive glycoprotein analysis, and opens a new avenue for the application of oriented-assembly nanochains.

Synthesis and application of BODIPY-based fluorescent labeling tag for oligosaccharide and N-linked glycan analysis by high-performance liquid chromatography with fluorescence detection

BACKGROUND

Glycosylation analysis is still challenging, not only because of the extreme structure complexity and conjugation diversity of glycans but also because of instrumental aspects such as the sensitivity limits of analyses. Therefore, glycan analysis by chromatographic methods is very often combined with fluorescence detection in addition to MS. The majority of fluorescent labeling employed before LC separation is based on 2-aminobenzamide, which has several disadvantages such as low labeling yield, poor fluorescence properties, and MS ionization efficiency. Therefore, even after several decades of development of new labels, there is still a need for new labeling tags with improved characteristics.

RESULTS

We present the application of a newly synthesized fluorescent label designed for oligosaccharide and glycan analysis by high-performance liquid chromatography with fluorescence detection (HPLC/FLD). The novel hydrazide derivative of dipyrrometheneboron difluoride (BODIPY) was synthesized from 2,4-dimethylpyrrole, methyl succinyl chloride, and boron trifluoride etherate followed by a reaction with hydrazine. The synthesized label was characterized by several analytical methods including NMR, UV/Vis and fluorescence spectroscopy, and mass spectrometry. The labeling reaction via hydrazone formation chemistry was optimized by labeling of maltooligosaccharide standards. The analysis of maltohexaose labeled by BODIPY-hydrazide followed by HPLC/FLD analysis provided the limit of detection in the low tens of femtomole. The presented method based on fluorescence detection is at least 30 times more sensitive than the standard approach employing labeling by 2-aminobenzamide. In addition, the labeling method by BODIPY-hydrazide was used for N-linked glycan profiling of several glycoproteins (ribonuclease B, immunoglobulin G) by RP-HPLC/FLD as well as HILIC/FLD analysis.

SIGNIFICANCE

This work represents the design, synthesis, and application of a new fluorescent label based on the BODIPY core and hydrazone formation chemistry for oligosaccharide and glycan analysis by HPLC/FLD. The proposed approach significantly improved the oligosaccharide and glycan analysis in comparison to the commonly used procedure employing 2-aminobenzamide.

Evaluation of solid-phase extraction sorbents for purification of oligosaccharides and glycans derivatized by positively charged labels followed by capillary electrophoretic analysis

The sample preparation including labeling and clean-up represents a key analytical step in the analysis of oligosaccharides and glycans by either chromatographic or electrophoretic separation methods. Although the majority of labeling has been performed by neutral and/or negatively charged tags, the introduction of a positive charge into the saccharide molecule can significantly improve the analysis, especially with mass spectrometry detection. In this work, we present the evaluation of five solid-phase extraction sorbents differing in extraction chemistry for the clean-up and concentration of positively labeled maltooligosaccharides from the reaction mixtures. Maltooligosaccharides containing four to seven glucose units were labeled by cationic tags (2-aminoethyl)trimethylammonium chloride and (carboxymethyl)trimethylammonium chloride hydrazide and the extraction conditions were optimized followed by electrophoretic analysis with conductivity detection. The effects of the solid-phase extraction sorbent chemistry, extraction conditions, and sample composition are discussed. All tested sorbents were capable of cleaning up maltooligosaccharides from the reaction mixtures to some extent after optimization of the solid-phase extraction procedure (51.9%-98.9% recovery). The best-rated amide-based sorbent was used to process the sample of N-linked glycans enzymatically released from ribonuclease B.

Myotube growth is associated with cancer-like metabolic reprogramming and is limited by phosphoglycerate dehydrogenase

The Warburg effect links growth and glycolysis in cancer. A key purpose of the Warburg effect is to generate glycolytic intermediates for anabolic reactions, such as nucleotides → RNA/DNA and amino acids → protein synthesis. The aim of this study was to investigate whether a similar 'glycolysis-for-anabolism' metabolic reprogramming also occurs in hypertrophying skeletal muscle. To interrogate this, we first induced C2C12 myotube hypertrophy with IGF-1. We then added 14C glucose to the differentiation medium and measured radioactivity in isolated protein and RNA to establish whether 14C had entered anabolism. We found that especially protein became radioactive, suggesting a glucose → glycolytic intermediates → non-essential amino acid(s) → protein series of reactions, the rate of which was increased by IGF-1. Next, to investigate the importance of glycolytic flux and non-essential amino acid synthesis for myotube hypertrophy, we exposed C2C12 and primary mouse myotubes to the glycolysis inhibitor 2-Deoxy-d-glucose (2DG). We found that inhibiting glycolysis lowered C2C12 and primary myotube size. Similarly, siRNA silencing of PHGDH, the key enzyme of the serine biosynthesis pathway, decreased C2C12 and primary myotube size; whereas retroviral PHGDH overexpression increased C2C12 myotube size. Together these results suggest that glycolysis is important for hypertrophying myotubes, which reprogram their metabolism to facilitate anabolism, similar to cancer cells.

EMNGly: predicting N-linked glycosylation sites using the language models for feature extraction

MOTIVATION

N-linked glycosylation is a frequently occurring post-translational protein modification that serves critical functions in protein folding, stability, trafficking, and recognition. Its involvement spans across multiple biological processes and alterations to this process can result in various diseases. Therefore, identifying N-linked glycosylation sites is imperative for comprehending the mechanisms and systems underlying glycosylation. Due to the inherent experimental complexities, machine learning and deep learning have become indispensable tools for predicting these sites.

RESULTS

In this context, a new approach called EMNGly has been proposed. The EMNGly approach utilizes pretrained protein language model (Evolutionary Scale Modeling) and pretrained protein structure model (Inverse Folding Model) for features extraction and support vector machine for classification. Ten-fold cross-validation and independent tests show that this approach has outperformed existing techniques. And it achieves Matthews Correlation Coefficient, sensitivity, specificity, and accuracy of 0.8282, 0.9343, 0.8934, and 0.9143, respectively on a benchmark independent test set.

Polyol recognition in catalysis: toward selective modification of glycosylated polypeptides with boronic acid-rhodium(II) catalysts

Proximity-induced methodologies for peptide and protein modification have been developed using recognition elements like inhibitors, antibodies, or affinity tags on amino acids. However, the recognition of saccharides for chemical modification remains widely unexplored. Studies exploring boronic acids and their derivatives have shown their alluring capabilities as selective molecular recognition elements for saccharides, and in this study we describe the application of these ideas to the discovery of a catalytic proximity-induced methodology for covalent modification of glycopeptides using boronic acids as a saccharide recognition element.

A universal UHPLC-CAD platform for the quantification of polysaccharide antigens

Several glycoconjugate-based vaccines against bacterial infections have been developed and licensed for human use. Polysaccharide (PS) analysis and characterization is therefore critical to profile the composition of polysaccharide-based vaccines. For PS content quantification, the majority of Ultra High Performance Liquid Chromatography (UHPLC) methods rely on the detection of selective monosaccharides constituting the PS repeating unit, therefore requiring chemical cleavage and tailored development: only a few methods directly quantify the intact PS. The introduction of charged aerosol detector (CAD) technology has improved the response of polysaccharide analytes, offering greater sensitivity than other detector sources (e.g., ELSD). Herein, we report the development of a universal UHPLC-CAD method (UniQS) for the quantification and quality evaluation of polysaccharide antigens (e.g., Streptococcus Pneumoniae, Neisseria meningitidis and Staphylococcus aureus). This work laid the foundation for a universal UHPLC-CAD format that could play an important role in future vaccine research and development helping to reduce time, efforts, and costs.

N-glycans from serum IgG and total serum glycoproteins specific for endometriosis

Endometriosis is a chronic inflammatory gynaecological disease characterized by the growth of endometrial tissue outside the uterine cavity. There are currently no definitive non-invasive diagnostic tools. Glycosylation is the most common posttranslational modification of proteins and altered glycosylation has been found in many diseases, including chronic inflammatory conditions and cancer. Sialylation and galactosylation on serum IgG have previously been found to be altered in endometriosis and serum sialylation changed after Zoladex (Goserelin Acetate) therapy. Using IgG and whole serum glycoproteins, we investigated N-glycosylation in two clinical cohorts of women with and without endometriosis. PNGase F-digested serum samples were fluorescently labelled and N-glycans were profiled by ultra-performance liquid chromatography. Clinical data was collected to link glycomic findings with metabolic and hormonal profiles. Total serum glycoprotein and IgG glycosylation differed in patients with endometriosis compared to control cases. The most significantly altered was glycan peak 3 from IgG, containing bisected biantennary glycans, which was decreased in the endometriosis cohorts (p = 0.0000005-0.018). In conclusion, this is the first pilot study to identify changes in N-glycans from whole serum glycoproteins associated with endometriosis. A larger validation study is now warranted and such studies should include the follow-up of surgically and pharmacologically treated patients.

Age-Related Changes in Post-Translational Modifications of Proteins from Whole Male and Female Skeletal Elements

One of the key questions in forensic cases relates to some form of age inference, whether this is how old a crime scene is, when in time a particular crime was committed, or how old the victim was at the time of the crime. These age-related estimations are currently achieved through morphological methods with varying degrees of accuracy. As a result, biomolecular approaches are considered of great interest, with the relative abundances of several protein markers already recognized for their potential forensic significance; however, one of the greatest advantages of proteomic investigations over genomics ones is the wide range of post-translational modifications (PTMs) that make for a complex but highly dynamic resource of information. Here, we explore the abundance of several PTMs including the glycosylation, deamidation, and oxidation of several key proteins (collagen, fetuin A, biglycan, serum albumin, fibronectin and osteopontin) as being of potential value to the development of an age estimation tool worthy of further evaluation in forensic contexts. We find that glycosylations lowered into adulthood but deamidation and oxidation increased in the same age range.

Expression of placental glycans and its role in regulating peripheral blood NK cells during preeclampsia: a perspective

Preeclampsia is a pregnancy-related multisystem disorder characterized by altered trophoblast invasion, oxidative stress, exacerbation of systemic inflammatory response, and endothelial damage. The pathogenesis includes hypertension and mild-to-severe microangiopathy in the kidney, liver, placenta, and brain. The main mechanisms involved in its pathogenesis have been proposed to limit trophoblast invasion and increase the release of extracellular vesicles from the syncytiotrophoblast into the maternal circulation, exacerbating the systemic inflammatory response. The placenta expresses glycans as part of its development and maternal immune tolerance during gestation. The expression profile of glycans at the maternal-fetal interface may play a fundamental role in physiological pregnancy changes and disorders such as preeclampsia. It is unclear whether glycans and their lectin-like receptors are involved in the mechanisms of maternal-fetal recognition by immune cells during pregnancy homeostasis. The expression profile of glycans appears to be altered in hypertensive disorders of pregnancy, which could lead to alterations in the placental microenvironment and vascular endothelium in pregnancy conditions such as preeclampsia. Glycans with immunomodulatory properties at the maternal-fetal interface are altered in early-onset severe preeclampsia, implying that innate immune system components, such as NK cells, exacerbate the systemic inflammatory response observed in preeclampsia. In this article, we discuss the evidence for the role of glycans in gestational physiology and the perspective of glycobiology on the pathophysiology of hypertensive disorders in gestation.

Advances in single-molecule junctions as tools for chemical and biochemical analysis

The development of miniaturized electronics has led to the design and construction of powerful experimental platforms capable of measuring electronic properties to the level of single molecules, along with new theoretical concepts to aid in the interpretation of the data. A new area of activity is now emerging concerned with repurposing the tools of molecular electronics for applications in chemical and biological analysis. Single-molecule junction techniques, such as the scanning tunnelling microscope break junction and related single-molecule circuit approaches have a remarkable capacity to transduce chemical information from individual molecules, sampled in real time, to electrical signals. In this Review, we discuss single-molecule junction approaches as emerging analytical tools for the chemical and biological sciences. We demonstrate how these analytical techniques are being extended to systems capable of probing chemical reaction mechanisms. We also examine how molecular junctions enable the detection of RNA, DNA, and traces of proteins in solution with limits of detection at the zeptomole level.

Innovative Metrics for Reporting and Comparing the Glycan Structural Profile in Biotherapeutics

Glycosylation is a critical quality attribute in biotherapeutics, impacting properties such as protein stability, solubility, clearance rate, efficacy, immunogenicity, and safety. Due to the heterogenic and complex nature of protein glycosylation, comprehensive characterization is demanding. Moreover, the lack of standardized metrics for evaluating and comparing glycosylation profiles hinders comparability studies and the establishment of manufacturing control strategies. To address both challenges, we propose a standardized approach based on novel metrics for a comprehensive glycosylation fingerprint which greatly facilitates the reporting and objective comparison of glycosylation profiles. The analytical workflow is based on a liquid chromatography-mass spectrometry-based multi-attribute method. Based on the analytical data, a matrix of glycosylation-related quality attributes, both at site-specific and whole molecule level, are computed, which provide metrics for a comprehensive product glycosylation fingerprint. Two case studies illustrate the applicability of the proposed indices as a standardized and versatile approach for reporting all dimensions of the glycosylation profile. The proposed approach further facilitates the assessments of risks associated with changes in the glycosylation profile that may affect efficacy, clearance, and immunogenicity.

Construction of dual-hydrophilic metal-organic framework with hierarchical porous structure for efficient glycopeptide enrichment

As an important role in life activities, it is necessary and important to study protein glycosylation. The pre-enrichment of N-glycopeptides is a significant step in glycoproteomics research. According to the inherent size, hydrophilicity and other properties of N-glycopeptides, affinity materials designed to match them will be able to separate N-glycopeptides from complex samples. In this work, we designed and prepared dual-hydrophilic hierarchical porous metal-organic frameworks (MOFs) nanospheres by metal-organic assembly (MOA) based template method and post-synthesis modification strategy. The hierarchical porous structure significantly improved the diffusion rate and binding sites for N-glycopeptide enrichment. Furthermore, the combination of hydrophilic MOFs and small molecules endowed the as-prepared MOFs nanospheres excellent hydrophilicity, which is conducive to the enrichment of N-glycopeptides based on hydrophilic interaction liquid chromatography (HILIC). Therefore, the nanospheres showed surprising enrichment ability for N-glycopeptides such as excellent selectivity (1/500, human serum immunoglobulin G/bovine serum albumin, m/m) and extremely low detective limitation (0.5 fmol). Meanwhile, 550 N-glycopeptides were identified from rat liver samples, proving its application potential in glycoproteomics research and providing design idea for porous affinity materials.

Facile fabrication of hydrophilic covalent organic framework composites for highly selective enrichment of N-glycopeptides

The development of facilely synthetic materials acts an essential role in glycoproteome analysis, especially for the highly efficient enrichment of N-linked glycopeptides. In this work, a facile and timesaving route was introduced in which COF_TP-TAPT served as a carrier and poly (ethylenimine) (PEI) and carrageenan (Carr) were successively coated on the surface via electrostatic interaction. The resultant COF_TP-TAPT@PEI@Carr showed remarkable performance in glycopeptide enrichment with high sensitivity (2 fmol μL^-1), high selectivity (1:800, molar ratio of human serum IgG to BSA digests), large loading capacity (300 mg g^-1), satisfactory recovery (102.4 ± 6.0%) and reusability (at least eight times). Due to the brilliant hydrophilicity and electrostatic interactions between COF_TP-TAPT@PEI@Carr and positively charged glycopeptides, the prepared materials could be applied in the identification and analysis in the human plasma of healthy subjects and patients with nasopharyngeal carcinoma. As a result, 113 N-glycopeptides with 141 glycosylation sites corresponding to 59 proteins and 144 N-glycopeptides with 177 glycosylation sites corresponding to 67 proteins were enriched from 2 μL plasma trypsin digests of the control groups and patients with nasopharyngeal carcinoma, respectively. 22 glycopeptides were identified only from the normal controls and 53 glycopeptides were detected only from the other set. The results demonstrated that this hydrophilic material was promising on a large scale and further N-glycoproteome research.

The Alterations of Serum N-glycome in Response to SARS-CoV-2 Vaccination

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused a global concern since its outbreak in 2019, with one of the main solutions being vaccination. Altered glycosylation has been described in patients after SARS-CoV-2 infection, while the effect of vaccination on serum glycoproteins remained unexplored. In this study, total serum glycosylation was analyzed in patients after SARS-CoV-2 infection and/or mRNA vaccination in order to identify potential glycosylation-based alterations. Enzyme-linked immunosorbent assay was applied to identify post-COVID-19 and post-Vaccinated patients and rule out potential outliers. Serum samples were deglycosylated by PNGase F digestion, and the released glycans were fluorescently derivatized using procainamide labeling. Solid-phase extraction was used to purify the labeled glycans followed by the analysis of hydrophilic-interaction liquid chromatography with fluorescence and mass-spectrometric detection. Alterations of serum N-glycome in response to SARS-CoV-2 infection and mRNA vaccination were revealed by linear discriminant analysis.

MS-based glycomics and glycoproteomics methods enabling isomeric characterization

Glycosylation is one of the most significant and abundant posttranslational modifications in mammalian cells. It mediates a wide range of biofunctions, including cell adhesion, cell communication, immune cell trafficking, and protein stability. Also, aberrant glycosylation has been associated with various diseases such as diabetes, Alzheimer's disease, inflammation, immune deficiencies, congenital disorders, and cancers. The alterations in the distributions of glycan and glycopeptide isomers are involved in the development and progression of several human diseases. However, the microheterogeneity of glycosylation brings a great challenge to glycomic and glycoproteomic analysis, including the characterization of isomers. Over several decades, different methods and approaches have been developed to facilitate the characterization of glycan and glycopeptide isomers. Mass spectrometry (MS) has been a powerful tool utilized for glycomic and glycoproteomic isomeric analysis due to its high sensitivity and rich structural information using different fragmentation techniques. However, a comprehensive characterization of glycan and glycopeptide isomers remains a challenge when utilizing MS alone. Therefore, various separation methods, including liquid chromatography, capillary electrophoresis, and ion mobility, were developed to resolve glycan and glycopeptide isomers before MS. These separation techniques were coupled to MS for a better identification and quantitation of glycan and glycopeptide isomers. Additionally, bioinformatic tools are essential for the automated processing of glycan and glycopeptide isomeric data to facilitate isomeric studies in biological cohorts. Here in this review, we discuss commonly employed MS-based techniques, separation hyphenated MS methods, and software, facilitating the separation, identification, and quantitation of glycan and glycopeptide isomers.

N-Linked Glycoproteome Analysis of Diosorea alata Tuber Shows Atypical Glycosylation and Indicates Central Role of Glycosylated Proteins in Tuber Maturation

Glycosylation is an important post translational modification in plants. First analysis of N-linked glycosylated proteins of Dioscorea alata using Concanavalin A lectin affinity chromatography enrichment coupled with label free quantification is presented. In total, 114 enriched glycoproteins were detected. Signal P and sub-cellular localization showed 42.2% of proteins to be secretory. These included peroxidases, endochitinases, calreticulin, calnexin, thaumatins and lipid transfer proteins. Gene Ontology and MapMan analysis predicted the enriched glycoproteins to be involved in processes essential for tuber maturation namely: signal transduction, lignification, protein trafficking, endoplasmic reticulum quality control and cell wall remodeling. This was supported by biochemical validation of the essential glycoproteins. Interestingly, out of the two dioscorin isoforms, Dio B was the only N-glycosylated form. In silico analysis showed O-glycosylation sites in the other form, Dio A suggesting its similarity with sporamin, the storage protein of sweet potato. Absence of signal peptide in Dio B and the presence of non-canonical motif hints towards its atypical glycosylation. The analysis revealed that N-glycosylation of Dio B isoform maintains the activities associated with Dioscorin at maturity and provides an overview of protein N-glycosylation, enriching the glycoproteome database of plants especially tubers.

Simultaneous N-Deglycosylation and Digestion of Complex Samples on S-Traps Enables Efficient Glycosite Hypothesis Generation

N-linked glycosylation is an important post-translational modification that is difficult to identify and quantify in traditional bottom-up proteomics experiments. Enzymatic deglycosylation of proteins by peptide:N-glycosidase F (PNGase F) prior to digestion and subsequent mass spectrometry analysis has been shown to improve coverage of various N-linked glycopeptides, but the inclusion of this step may add up to a day to an already lengthy sample preparation process. An efficient way to integrate deglycosylation with bottom-up proteomics would be a valuable contribution to the glycoproteomics field. Here, we demonstrate a proteomics workflow in which deglycosylation and proteolytic digestion of samples occur simultaneously using suspension trapping (S-Trap). This approach adds no time to standard digestion protocols. Applying this sample preparation strategy to a human serum sample, we demonstrate improved identification of potential N-glycosylated peptides in deglycosylated samples compared with non-deglycosylated samples, identifying 156 unique peptides that contain the N-glycosylation motif (asparagine-X-serine/threonine), the deamidation modification characteristic of PNGase F, and an increase in peptide intensity over a control sample. We expect that this rapid sample preparation strategy will assist in the identification and quantification of both known and potential glycoproteins. Data are available via ProteomeXchange with the identifier PXD037921.

Heritability of the glycan clock of biological age

Immunoglobulin G is posttranslationally modified by the addition of complex N-glycans affecting its function and mediating inflammation at multiple levels. IgG glycome composition changes with age and health in a predictive pattern, presumably due to inflammaging. As a result, a novel biological aging biomarker, glycan clock of age, was developed. Glycan clock of age is the first of biological aging clocks for which multiple studies showed a possibility of clock reversal even with simple lifestyle interventions. However, none of the previous studies determined to which extent the glycan clock can be turned, and how much is fixed by genetic predisposition. To determine the contribution of genetic and environmental factors to phenotypic variation of the glycan clock, we performed heritability analysis on two TwinsUK female cohorts. IgG glycans from monozygotic and dizygotic twin pairs were analyzed by UHPLC and glycan age was calculated using the glycan clock. In order to determine additive genetic, shared, and unique environmental contributions, a classical twin design was applied. Heritability of the glycan clock was calculated for participants of one cross-sectional and one longitudinal cohort with three time points to assess the reliability of measurements. Heritability estimate for the glycan clock was 39% on average, suggesting a moderate contribution of additive genetic factors (A) to glycan clock variation. Remarkably, heritability estimates remained approximately the same in all time points of the longitudinal study, even though IgG glycome composition changed substantially. Most environmental contributions came from shared environmental factors (C), with unique environmental factors (E) having a minor role. Interestingly, heritability estimates nearly doubled, to an average of 71%, when we included age as a covariant. This intervention also inflated the estimates of unique environmental factors contributing to glycan clock variation. A complex interplay between genetic and environmental factors defines alternative IgG glycosylation during aging and, consequently, dictates the glycan clock's ticking. Apparently, environmental factors (including lifestyle choices) have a strong impact on the biological age measured with the glycan clock, which additionally clarifies why this aging clock is one of the most potent biomarkers of biological aging.

Safe Sialidase Production by the Saprophyte Oerskovia paurometabola: Gene Sequence and Enzyme Purification

Sialidase preparations are applied in structural and functional studies on sialoglycans, in the production of sialylated therapeutic proteins and synthetic substrates for use in biochemical research, etc. They are obtained mainly from pathogenic microorganisms; therefore, the demand for apathogenic producers of sialidase is of exceptional importance for the safe production of this enzyme. Here, we report for the first time the presence of a sialidase gene and enzyme in the saprophytic actinomycete Oerskovia paurometabola strain O129. An electrophoretically pure, glycosylated enzyme with a molecular weight of 70 kDa was obtained after a two-step chromatographic procedure using DEAE cellulose and Q-sepharose. The biochemical characterization showed that the enzyme is extracellular, inductive, and able to cleave α(2→3,6,8) linked sialic acids with preference for α(2→3) bonds. The enzyme production was strongly induced by glycomacropeptide (GMP) from milk whey, as well as by sialic acid. Investigation of the deduced amino acid sequence revealed that the protein molecule has the typical six-bladed β-propeller structure and contains all features of bacterial sialidases, i.e., an YRIP motif, five Asp-boxes, and the conserved amino acids in the active site. The presence of an unusual signal peptide of 40 amino acids was predicted. The sialidase-producing O. paurometabola O129 showed high and constant enzyme production. Together with its saprophytic nature, this makes it a reliable producer with high potential for industrial application.

Recent development in hydrophilic interaction liquid chromatography stationary materials for glycopeptide analysis

Protein glycosylation is one of the most important post-translational modifications, and aberrant glycosylation is associated with the occurrence and development of diseases. Deciphering abnormal glycosylation changes can identify disease-specific signatures to facilitate the discovery of potential disease biomarkers. However, glycosylation analysis is challenging due to the diversity of glycans, heterogeneity of glycosites, and poor electrospray ionization of mass spectrometry. To overcome these obstacles, glycosylation is often elucidated using enriched glycopeptides by removing highly abundant non-glycopeptides. Hydrophilic interaction liquid chromatography (HILIC) is widely used for glycopeptide enrichment due to its excellent selectivity and specificity to hydrophilic glycans and compatibility with mass spectrometry. However, the development of HILIC has lagged far behind hydrophobic interaction chromatography, so efforts to further improve the performance of HILIC are beneficial for glycosylation analysis. This review discusses recent developments in HILIC materials and their advanced applications. Based on the physiochemical properties of glycopeptides, the use of amino acids or peptides as stationary phases showed improved enrichment and separation of glycopeptides. We can envision that the use of glycopeptides as stationary phases would definitely further improve the selectivity and specificity of HILIC for glycosylation analysis.

Protonated α-N-Acetyl Galactose Glycopeptide Dissociation Chemistry

We recently provided mass spectrometric, H/D labeling, and computational evidence of pyranose to furanose N-acetylated ion isomerization reactions that occurred prior to glycosidic bond cleavage in both O- and N-linked glycosylated amino acid model systems (Guan et al. Phys. Chem. Chem. Phys., 2021, 23, 23256-23266). These reactions occurred irrespective of the glycosidic linkage stereochemistry (α or β) and the N-acetylated hexose structure (GlcNAc or GalNAc). In the present article, we test the generality of the preceding findings by examining threonyl α-GalNAc-glycosylated peptides. We utilize computational chemistry to compare the various dissociation and isomerization pathways accessible with collisional activation. We then interrogate the structure(s) of the resulting charged glycan and peptide fragments with infrared "action" spectroscopy. Isomerization of the original pyranose, the protonated glycopeptide [AT(GalNAc)A+H]⁺, is predicted to be facile compared to direct dissociation, as is the glycosidic bond cleavage of the newly formed furanose form, i.e., furanose oxazolinium ion structures are predicted to predominate. IR action spectra for the m/z 204, C₈H₁₄N₁O₅⁺, glycan fragment population support this prediction. The IR action spectra of the complementary m/z 262 peptide fragment were assigned as a mixture of the lowest-energy structures of [ATA+H]⁺ consistent with the literature. If general, the change to a furanose m/z 204 product ion structure fundamentally alters the ion population available for MS³ dissociation and glycopeptide sequence identification.

Identification of Mobility-Resolved N-Glycan Isomers

Glycan analysis has evolved considerably during the last decade. The advent of high-resolution ion-mobility spectrometry has enabled the separation of isomers with only the slightest of structural differences. However, the ability to separate such species raises the problem of identifying all the mobility-resolved peaks that are observed, especially when analytical standards are not available. In this work, we report an approach based on the combination of IMSⁿ with cryogenic vibrational spectroscopy to identify N-glycan reducing-end anomers. By identifying the reducing-end α and β anomers of diacetyl-chitobiose, which is a disaccharide that forms part of the common core of all N-glycans, we are able to assign mobility peaks to reducing anomers of a selection of N-glycans of different sizes, starting from trisaccharides such as Man-1 up to glycans containing nine monosaccharide units, such as G2. By building an infrared fingerprint database of the identified N-glycans, our approach allows unambiguous identification of mobility peaks corresponding to reducing-end anomers and distinguishes them from positional isomers that might be present in a complex mixture.

Determination of Amide Cis/Trans Isomers in N-Acetyl-d-glucosamine: Tailored NMR Analysis of the N-Acetyl Group Conformation

N‐Acetyl‐d‐glucosamine (GlcNAc) is one of the most common amino sugars in nature, but the conformation of its N‐acetyl group has drawn little attention. We report herein the first identification of NH protons of the amide cis forms of α‐ and β‐GlcNAc by NMR spectroscopy. Relative quantification and thermodynamic analysis of both cis and trans forms was carried out in aqueous solution. The NH protons were further utilized by adapting protein NMR experiments to measure eight J‐couplings within the N‐acetyl group, of which six are sensitive to the H2‐NH conformation and two are sensitive to the amide conformation. For amide cis and trans forms, the orientation between H2 and NH was determined as anti conformation, while a small percentage of syn conformation was predicted for the amide trans form of β‐GlcNAc. This approach holds great promise for the detailed conformational analysis of GlcNAc in larger biomolecules, such as glycoproteins and polysaccharides.

A New Strategy Coupling Ion-Mobility-Selective CID and Cryogenic IR Spectroscopy to Identify Glycan Anomers

Determining the primary structure of glycans remains challenging due to their isomeric complexity. While high-resolution ion mobility spectrometry (IMS) has recently allowed distinguishing between many glycan isomers, the arrival-time distributions (ATDs) frequently exhibit multiple peaks, which can arise from positional isomers, reducing-end anomers, or different conformations. Here, we present the combination of ultrahigh-resolution ion mobility, collision-induced dissociation (CID), and cryogenic infrared (IR) spectroscopy as a systematic method to identify reducing-end anomers of glycans. Previous studies have suggested that high-resolution ion mobility of sodiated glycans is able to separate the two reducing-end anomers. In this case, Y-fragments generated from mobility-separated precursor species should also contain a single anomer at their reducing end. We confirm that this is the case by comparing the IR spectra of selected Y-fragments to those of anomerically pure mono- and disaccharides, allowing the assignment of the mobility-separated precursor and its IR spectrum to a single reducing-end anomer. The anomerically pure precursor glycans can henceforth be rapidly identified on the basis of their IR spectrum alone, allowing them to be distinguished from other isomeric forms.

Mass Spectrometry-Based Techniques to Elucidate the Sugar Code

Cells encode information in the sequence of biopolymers, such as nucleic acids, proteins, and glycans. Although glycans are essential to all living organisms, surprisingly little is known about the "sugar code" and the biological roles of these molecules. The reason glycobiology lags behind its counterparts dealing with nucleic acids and proteins lies in the complexity of carbohydrate structures, which renders their analysis extremely challenging. Building blocks that may differ only in the configuration of a single stereocenter, combined with the vast possibilities to connect monosaccharide units, lead to an immense variety of isomers, which poses a formidable challenge to conventional mass spectrometry. In recent years, however, a combination of innovative ion activation methods, commercialization of ion mobility-mass spectrometry, progress in gas-phase ion spectroscopy, and advances in computational chemistry have led to a revolution in mass spectrometry-based glycan analysis. The present review focuses on the above techniques that expanded the traditional glycomics toolkit and provided spectacular insight into the structure of these fascinating biomolecules. To emphasize the specific challenges associated with them, major classes of mammalian glycans are discussed in separate sections. By doing so, we aim to put the spotlight on the most important element of glycobiology: the glycans themselves.

Comparative study for analysis of carbohydrates in biological samples

This work presents a comparative study for the analysis of carbohydrates for four common chromatographic methods, each coupled to mass spectrometry. Supercritical fluid chromatography (SFC), hydrophilic interaction liquid chromatography (HILIC), reversed-phase liquid chromatography (RP-LC) and gas chromatography (GC) with detection by triple quadrupole mass spectrometer (QqQ-MS) are compared. It is shown that gas chromatography and reversed-phase liquid chromatography, each after derivatisation, are superior to the other two methods in terms of separation performance. Furthermore, comparing the different working modes of the mass spectrometer, it can be determined that a targeted analysis, i.e. moving from full scan to single ion monitoring (SIM) and multiple reaction monitoring (MRM), results in an improvement in the sensitivity as well as the repeatability of the method, which has deficiencies especially in the analysis using HILIC. Overall, RP-LC-MS in MRM after derivatisation with 1-phenyl-3-methyl-5-pyrazolone (PMP) proved to be the most suitable method in terms of separation performance, sensitivity and repeatability for the analysis of monosaccharides. Detection limits in the nanomolar range were achieved, which corresponds to a mass concentration in the low µg/L range. The applicability of this method to different biological samples was investigated with various herbal liquors, pectins and a human glycoprotein.

Changes in Serum N-Glycome for Risk Drinkers: A Comparison with Standard Markers for Alcohol Abuse in Men and Women

Background and aim: Glycomic alterations serve as biomarker tools for different diseases. The present study aims to evaluate the diagnostic capability of serum N-glycosylation to identify alcohol risk drinking in comparison with standard markers. Methods: We included 1516 adult individuals (age range 18–91 years; 55.3% women), randomly selected from a general population. A total of 143 (21.0%) men and 50 (5.9%) women were classified as risk drinkers after quantification of daily alcohol consumption and the Alcohol Use Disorders Identification Test (AUDIT). Hydrophilic interaction ultra-performance liquid chromatography (HILIC-UPLC) was used for the quantification of 46 serum N-glycan peaks. Serum gamma-glutamyltransferase (GGT), carbohydrate-deficient transferrin (CDT), and red blood cell mean corpuscular volume (MCV) were measured by standard clinical laboratory methods. Results: Variations in serum N-glycome associated risk drinking were more prominent in men compared to women. A unique combination of N-glycan peaks selected by the selbal algorithm shows good discrimination between risk-drinkers and non-risk drinkers for men and women. Receiver operating characteristics (ROC) curves show accuracy for the diagnosis of risk drinking, which is comparable to that of the golden standards, GGT, MCV and CDT markers for men and women. Additionally, the inclusion of N-glycan peaks improves the diagnostic accuracy of the standard markers, although it remains relatively low, due to low sensitivity. For men, the area under the ROC curve using N-glycome data is 0.75, 0.76, and 0.77 when combined with GGT, MCV, and CDT, respectively. In women, the areas were 0.76, 0.73, and 0.73, respectively. Conclusion: Risk drinking is associated with significant variations in the serum N-glycome, which highlights its potential diagnostic utility.

Surface Shave: Revealing the Apical-Restricted Uroglycome

This study aimed to investigate the highly differentiated urothelial apical surface glycome. The functions of the mammalian urothelium, lining the majority of the urinary tract and providing a barrier against toxins in urine, are dependent on the correct differentiation of urothelial cells, relying on protein expression, modification, and complex assembly to regulate the formation of multiple differentiated cell layers. Protein glycosylation, a poorly studied aspect of urothelial differentiation, contributes to the apical glycome and is implicated in the development of urothelial diseases. To enable surface glycome characterization, we developed a method to collect tissue apical surface N- and O-glycans. A simple, novel device using basic laboratory supplies was developed for enzymatic shaving of the luminal bladder urothelial surface, with subsequent release and mass spectrometric analysis of apical surface O- and N-glycans, the first normal mammalian urothelial N-glycome to be defined. Trypsinization of superficial glycoproteins was tracked using immunolabeling of the apically expressed uroplakin 3a protein to optimize enzymatic release, without compromising the integrity of the superficial urothelial layer. The approach developed for releasing apical tissue surface glycans allowed for comparison with the N-glycome of the total porcine bladder urothelial cells and thus identification of apical surface glycans as candidates implicated in the urothelial barrier function. Data are available in MassIve: MSV000087851.

Post-synthesis modification of covalent organic frameworks for ultrahigh enrichment of low-abundance glycopeptides from human saliva and serum

In this study, a novel type of covalent organic framework (COF) material rich in boronic acid sites was prepared through post-synthesis modification (TbBD@PEI@Au@4-MPBA). The surface of COF material had abundant carboxylic acid groups, which could bind a large amount of polyethyleneimine (PEI) through electrostatic interaction. At the same time, the amino groups on the PEI can be grafted with Au nanoparticles (Au NPs) in situ, and then 4-mercaptophenylboronic acid (4-MPBA) was modified by the reaction of Au and sulfhydryl groups. The massive grafting of boronic acid groups made the material's enrichment effect on glycopeptides expected. The results of experiments indicated that the composite material has high sensitivity (5 amol μL^-1) and selectivity (1:1000). In addition, the material has outstanding stability and reusability, with a load capacity of about 100 mg g^-1 and a recovery of 99.3 ± 2.2%. What's more, after enriched by TbBD@PEI@Au@4-MPBA, 56 endogenous glycopeptides from fresh human saliva were detected by MALDI-TOF MS, 56 unique glycopeptides corresponding to 31 glycoproteins from human saliva and 513 unique glycopeptides corresponding to 208 glycoproteins from serum of throat cancer patient were detected by nano-LC-MS/MS, respectively, which was expected to be applied to glycoproteomics research.

Toward High-Throughput Cryogenic IR Fingerprinting of Mobility-Separated Glycan Isomers

Infrared (IR) spectroscopy is a powerful tool used to infer detailed structural information on molecules, often in conjunction with quantum-chemical calculations. When applied to cryogenically cooled ions, IR spectra provide unique fingerprints that can be used for biomolecular identification. This is particularly important in the analysis of isomeric biopolymers, which are difficult to distinguish using mass spectrometry. However, IR spectroscopy typically requires laser systems that need substantial user attention and measurement times of tens of minutes, which limits its analytical utility. We report here the development of a new high-throughput instrument that combines ultrahigh-resolution ion-mobility spectrometry with cryogenic IR spectroscopy and mass spectrometry, and we apply it to the analysis of isomeric glycans. The ion mobility step, which is based on structures for lossless ion manipulations (SLIM), separates glycan isomers, and an IR fingerprint spectrum identifies them. An innovative cryogenic ion trap allows multiplexing the acquisition of analyte IR fingerprints following mobility separation, and using a turn-key IR laser, we can obtain spectra and identify isomeric species in less than a minute. This work demonstrates the potential of IR fingerprinting methods to impact the analysis of isomeric biomolecules and more specifically glycans.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.

Non-derivatization strategy for the comprehensive characterization of neutral monosaccharide isomers and neutral disaccharide isomers using hydrophilic interaction liquid chromatography coupled to quadrupole/time-of-flight mass spectrometry

Monosaccharide isomers and disaccharide isomers widely exist in nature, playing a key role in a number of important biological processes. However, due to high structural similarity and high polarity, the characterization of monosaccharide isomers, disaccharide isomers, as well as the analysis of monosaccharide composition of polysaccharides by a method that does not require derivatization is an ongoing challenge. Herein, we proposed a simple method for rapid discrimination of non-derivatized neutral monosaccharide, and disaccharide isomers using hydrophilic interaction liquid chromatography coupled to quadrupole/time-of-flight mass spectrometry (HILIC-Q/TOF-MS). In this work, we optimized the experimental parameters, and detailed approaches to discriminate the precursor ions, deprotonated ions, and fragment ions are proposed, as well. To discriminate the various ions, the retention times, the relative abundance (RA) of precursor ions and fragment ions at different collision energies, the relative abundance ratio (RAR) of fragment ions to deprotonated ions or precursor ions were considered for characterization of neutral monosaccharide and disaccharide isomers. Finally, this strategy was successfully applied to analyzing the monosaccharide composition of neutral disaccharides, polysaccharides, and an aqueous extract of Moringa oleifera seeds. The experimental results revealed that the HILIC-Q/TOF-MS is an effective and convenient strategy for rapid differentiation of monosaccharide isomers and disaccharide isomers, which may serve as a general platform for the analysis of neutral polysaccharides, food, medicinal plants, and herbs.