An enrichment method based on synergistic and reversible covalent interactions for large-scale analysis of glycoproteins

Comprehensive O-Glycan Analysis by Porous Graphitized Carbon Nanoliquid Chromatography-Mass Spectrometry

The diverse and unpredictable structures of O-GalNAc-type protein glycosylation present a challenge for its structural and functional characterization in a biological system. Porous graphitized carbon (PGC) liquid chromatography (LC) coupled to mass spectrometry (MS) has become one of the most powerful methods for the global analysis of glycans in complex biological samples, mainly due to the extensive chromatographic separation of (isomeric) glycan structures and the information delivered by collision induced fragmentation in negative mode MS for structural elucidation. However, current PGC-based methodologies fail to detect the smaller glycan species consisting of one or two monosaccharides, such as the Tn (single GalNAc) antigen, which is broadly implicated in cancer biology. This limitation is caused by the loss of small saccharides during sample preparation and LC. Here, we improved the conventional PGC nano-LC-MS/MS-based strategy for O-glycan analysis, enabling the detection of truncated O-glycan species and improving isomer separation. This was achieved by the implementation of 2.7 μm PGC particles in both the trap and analytical LC columns, which provided an enhanced binding capacity and isomer separation for O-glycans. Furthermore, a novel mixed-mode PGC-boronic acid-solid phase extraction during sample preparation was established to purify a broad range of glycans in an unbiased manner, including the previously missed mono- and disaccharides. Taken together, the optimized PGC nano-LC-MS/MS platform presents a powerful component of the toolbox for comprehensive O-glycan characterization.

Towards chemoenzymatic labeling strategies for profiling protein glycosylation

Protein glycosylation is one of the most common and important post-translational modifications of proteins involved in regulating glycoprotein functions. The chemoenzymatic glycan labeling strategy allows rapid, efficient, and selective interrogation of glycoproteins. Glycoproteomics identifies protein glycosylation events at a large scale, providing information such as peptide sequences, glycan structures, and glycosylated sites. This review discusses the recent development of chemoenzymatic labeling strategies for glycoprotein analysis, mainly including glycoprotein and glycosite profiling. Furthermore, we highlight the chemoenzymatic enrichment approaches in mass spectrometry analysis for three classes of glycan modifications, including N-glycosylation, O-GlcNAcylation, and mucin-type O-glycosylation. Finally, we highlight the emerging trends in new tools and cutting-edge technologies available for glycoproteomic research.

Functional Interface for Glycoprotein Sensing: Focusing on Biosensors

Glycosylated proteins or glycoproteins make up a large family of glycoconjugates, and they participate in a variety of fundamental biological events. Glycoproteins have become important biomarkers in the diagnosis and treatment of a number of tumors. Biosensors are quite suitable for glycoprotein detection. The design and fabrication of a functional sensing interface play a crucial role in the biosensor construction to target glycoproteins. The functional interface, particularly receptors, typically determines the key characteristics of a biosensor, such as selectivity and sensitivity. Antibody, peptide, aptamer, boronic acid derivative, lectin, and molecularly imprinted polymer are all capable receptors for glycoprotein recognition, and each of these will be discussed. Most glycoproteins exist in low abundance, thus rendering signal amplification techniques indispensable. Nucleic acid-mediated and nanomaterial-mediated signal amplification for the detection of glycoproteins will be focused on herein. This review aims to highlight these different functional interfaces for glycoprotein sensing.

Nanoparticles for inducing Gaucher disease-like damage in cancer cells

Nutrient avidity is one of the most distinctive features of tumours. However, nutrient deprivation has yielded limited clinical benefits. In Gaucher disease, an inherited metabolic disorder, cells produce cholesteryl-glucoside which accumulates in lysosomes and causes cell damage. Here we develop a nanoparticle (AbCholB) to emulate natural-lipoprotein-carried cholesterol and initiate Gaucher disease-like damage in cancer cells. AbCholB is composed of a phenylboronic-acid-modified cholesterol (CholB) and albumin. Cancer cells uptake the nanoparticles into lysosomes, where CholB reacts with glucose and generates a cholesteryl-glucoside-like structure that resists degradation and aggregates into microscale crystals, causing Gaucher disease-like damage in a glucose-dependent manner. In addition, the nutrient-sensing function of mTOR is suppressed. It is observed that normal cells escape severe damage due to their inferior ability to compete for nutrients compared with cancer cells. This work provides a bioinspired strategy to selectively impede the metabolic action of cancer cells by taking advantage of their nutrient avidity.

Integrating the analysis of human biopsies using post-translational modifications proteomics

Proteome diversities and their biological functions are significantly amplified by post-translational modifications (PTMs) of proteins. Shotgun proteomics, which does not typically survey PTMs, provides an incomplete picture of the complexity of human biopsies in health and disease. Recent advances in mass spectrometry-based proteomic techniques that enrich and study PTMs are helping to uncover molecular detail from the cellular level to system-wide functions, including how the microbiome impacts human diseases. Protein heterogeneity and disease complexity are challenging factors that make it difficult to characterize and treat disease. The search for clinical biomarkers to characterize disease mechanisms and complexity related to patient diagnoses and treatment has proven challenging. Knowledge of PTMs is fundamentally lacking. Characterization of complex human samples that clarify the role of PTMs and the microbiome in human diseases will result in new discoveries. This review highlights the key role of proteomic techniques used to characterize unknown biological functions of PTMs derived from complex human biopsies. Through the integration of diverse methods used to profile PTMs, this review explores the genetic regulation of proteoforms, cells of origin expressing specific proteins, and several bioactive PTMs and their subsequent analyses by liquid chromatography and tandem mass spectrometry.

Medical Relevance, State-of-the-Art and Perspectives of "Sweet Metacode" in Liquid Biopsy Approaches

This review briefly introduces readers to an area where glycomics meets modern oncodiagnostics with a focus on the analysis of sialic acid (Neu5Ac)-terminated structures. We present the biochemical perspective of aberrant sialylation during tumourigenesis and its significance, as well as an analytical perspective on the detection of these structures using different approaches for diagnostic and therapeutic purposes. We also provide a comparison to other established liquid biopsy approaches, and we mathematically define an early-stage cancer based on the overall prognosis and effect of these approaches on the patient's quality of life. Finally, some barriers including regulations and quality of clinical validations data are discussed, and a perspective and major challenges in this area are summarised.

Glycan-specific molecularly imprinted polymers towards cancer diagnostics: merits, applications, and future perspectives

Aberrant glycans are a hallmark of cancer states. Notably, emerging evidence has demonstrated that the diagnosis of cancers with tumour-specific glycan patterns holds great potential to address unmet medical needs, especially in improving diagnostic sensitivity and selectivity. However, despite vast glycans having been identified as potent markers, glycan-based diagnostic methods remain largely limited in clinical practice. There are several reasons that prevent them from reaching the market, and the lack of anti-glycan antibodies is one of the most challenging hurdles. With the increasing need for accelerating the translational process, numerous efforts have been made to find antibody alternatives, such as lectins, boronic acids and aptamers. However, issues concerning affinity, selectivity, stability and versatility are yet to be fully addressed. Molecularly imprinted polymers (MIPs), synthetic antibody mimics with tailored cavities for target molecules, hold the potential to revolutionize this dismal progress. MIPs can bind a wide range of glycan markers, even those without specific antibodies. This capacity effectively broadens the clinical applicability of glycan-based diagnostics. Additionally, glycoform-resolved diagnosis can also be achieved through customization of MIPs, allowing for more precise diagnostic applications. In this review, we intent to introduce the current status of glycans as potential biomarkers and critically evaluate the challenges that hinder the development of in vitro diagnostic assays, with a particular focus on glycan-specific recognition entities. Moreover, we highlight the key role of MIPs in this area and provide examples of their successful use. Finally, we conclude the review with the remaining challenges, future outlook, and emerging opportunities.

An efficient strategy with a synergistic effect of hydrophilic and electrostatic interactions for simultaneous enrichment of N- and O-glycopeptides

N- and O-glycosylation modifications of proteins are closely linked to the onset and development of many diseases and have gained widespread attention as potential targets for therapy and diagnosis. However, the low abundance and low ionization efficiency of glycopeptides as well as the high heterogeneity make glycosylation analysis challenging. Here, an enrichment strategy, using Knoevenagel copolymers modified with polydopamine-adenosine (denoted as PDA-ADE@KCP), was firstly proposed for simultaneous enrichment of N- and O-glycopeptides through the synergistic effects of hydrophilic and electrostatic interactions. The adjustable charged surface and hydrophilic properties endow the material with the capability to achieve effective enrichment of intact N- and O-glycopeptides. The experimental results exhibited excellent selectivity (1 : 5000) and sensitivity (0.1 fmol μL-1) of the prepared material for N-glycopeptides from standard protein digest samples. Moreover, it was further applied to simultaneous capturing of N- and O-glycopeptides from mouse liver protein digests. Compared to the commercially available zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) material, the number of glycoproteins corresponding to all N- and O-glycopeptides enriched with PDA-ADE@KCP was much more than that with ZIC-HILIC. Furthermore, PDA-ADE@KCP captured more O-glycopeptides than ZIC-HILIC, revealing its superior performance in O-glycopeptide enrichment. All these results indicated that the strategy holds immense potential in characterizing N- and O-intact glycopeptides in the field of proteomics.

Hydrophilic Peptide and Glycopeptide as Immobilized Sorbents for Glycosylation Analysis

Hydrophilic interaction liquid chromatography (HILIC) is widely used for glycopeptide enrichment in shot-gun glycoproteomics to enhance the glycopeptide signal and minimize the ionization competition of peptides. In this work, we have developed a novel hydrophilic material (glycoHILIC) based on glycopeptides and peptides to provide hydrophilic properties. GlycoHILIC was synthesized by oxidizing cotton and then reacting the resulting aldehyde with the N-terminus of the glycopeptide or peptide by reductive amination. Due to the large amount of hydrophilic carbohydrates and hydrophilic amino acids contained in glycopeptides, glycoHILIC showed significantly better enrichment of glycopeptides than cotton itself. Our results demonstrate that glycoHILIC has high selectivity, a low detection limit, and good stability. Over 257 unique N-linked glycosylation sites in 1477 intact N-glycopeptides from 146 glycoproteins were identified from 1 μL of human serum using glycoHILIC. Serum analysis of pancreatic cancer patients found that 38 N-glycopeptides among 21 glycoproteins changed significantly, of which 7 N-glycopeptides increased and 31 N-glycopeptides decreased. These results demonstrate that glycoHILIC can be used for glycopeptide enrichment and analysis.

Dual-ligand hydrogen-bonded organic framework: Tailored for mono-phosphopeptides and glycopeptides analysis

Hydrogen-bonded organic frameworks (HOFs) have emerged as a promising class of materials for applications of separation and enrichment. Utilizing multiple-ligands to construct HOFs is a promising avenue towards the development of structurally stable and functionally diverse frameworks, offering opportunities to create customized binding sites for selective recognition of biomolecules. In recent years, due to the crucial role that protein post-translational modifications (PTMs) play in maintaining protein function and regulating signaling pathways, and the growing recognition of the extensive cross-talk that can occur between PTMs, simultaneous analysis of different types of PTMs represents a requirement of a new generation of enrichment materials. Here, for the first attempt, we report a dual-ligand HOF constructed from borate anion and guanidinium cation for the simultaneous identification of glycopeptides and phosphopeptides, especially mono-phosphopeptides. According to theoretical calculations, the HOF functional sites display a synergistic "matching" effect with mono-phosphopeptides, resulting in a stronger enrichment effect for mono-phosphopeptides as compared to multi-phosphopeptides. Also, due to its high hydrophilicity and boronate affinity, this material can efficiently capture glycoproteins. HOF is set to become an active research direction in the development of highly efficient simultaneous protein enrichment materials, and offers a new approach for comprehensive PTMs analysis.

Water-stable hydrophilic metal organic framework composite for the recognition of N-glycopeptides during diabetes progression by mass spectrometry

A hydrophilic Al-MOFs composite was prepared using cheap and available reagents in water via a suitable large-scale production, an economical and environment-friendly method for capturing N-glycopeptides. The prepared Al-MOFs composite with high hydrolytically stable and hydrophilic 1D channels exhibits an ultralow detection limit (0.5 fmol/μL), and excellent reusability (at least 10 cycles) in the capture of N-glycopeptides from standard bio-samples. Interestingly, the Al-MOFs composite also shows remarkable performance in practical applications, where 300 N-glycopeptides ascribed to 124 glycoproteins were identified in 1 µL human serum and were successfully applied in profiling the differences of N-glycopeptides during diabetes progression. Moreover, 12 specific glycoproteins used as biomarkers to accurately distinguish the progression of diabetes are identified. The present work provides a potential commercial method for large-scale glycoproteomics research in complex clinical samples while offering new guidance for the precise diagnosis of diabetes progression.

Common Post-translational Modifications (PTMs) of Proteins: Analysis by Up-to-Date Analytical Techniques with an Emphasis on Barley

Post-translational modifications (PTMs) of biomacromolecules can be useful for understanding the processes by which a relatively small number of individual genes in a particular genome can generate enormous biological complexity in different organisms. The proteomes of barley and the brewing process were investigated by different techniques. However, their diverse and complex PTMs remain understudied. As standard analytical approaches have limitations, innovative analytical approaches need to be developed and applied in PTM studies. To make further progress in this field, it is necessary to specify the sites of modification, as well as to characterize individual isoforms with increased selectivity and sensitivity. This review summarizes advances in the PTM analysis of barley proteins, particularly those involving mass spectrometric detection. Our focus is on monitoring phosphorylation, glycation, and glycosylation, which critically influence functional behavior in metabolism and regulation in organisms.

Large-Scale and Site-Specific Mapping of the Murine Brain O-Glycoproteome with IMPa

Altered protein glycosylation is typically associated with cognitive defects and other phenotypes, but there is a lack of knowledge about the brain glycoproteome. Here, we used the newly available O-glycoprotease IMPa from Pseudomonas aeruginosa for comprehensive O-glycoproteomic analyses of the mouse brain. In this approach, total tryptic glycopeptides were prepared, extracted, purified, and conjugated to a solid support before an enzymatic cleavage by IMPa. O-glycopeptides were analyzed by electron-transfer/higher-energy collision dissociation (EThcD), which permits site-specific and global analysis of all types of O-glycans. We developed two complementary approaches for the analysis of the total O-glycoproteome using HEK293 cells and derivatives. The results demonstrated that IMPa and EThcD facilitate the confident localization of O-glycans on glycopeptides. We then applied these approaches to characterize the O-glycoproteome of the mouse brain, which revealed the high frequency of various sialylated O-glycans along with the unusual presence of the Tn antigen. Unexpectedly, the results demonstrated that glycoproteins in the brain O-glycoproteome only partly overlap with those reported for the brain N-glycoproteome. These approaches will aid in identifying the novel O-glycoproteomes of different cells and tissues and foster clinical and translational insights into the functions of protein O-glycosylation in the brain and other organs.

Design and investigation of targeting agent orientation and density on nanoparticles for enhancing cellular uptake efficiency

The design of targeting agent-conjugated systems is attracting much attention in cell targeted delivery and cancer therapy. However, quantitative study of the ligand density and binding efficiency is still limited due to the technical matters and tedious work involved. In this article, benzoboroxole-modified core-shell magnetic nanoparticles (MSP-AOPB NPs) as a drug carrier model were fabricated and transferrin (Tf) was immobilized on the nanoparticle surface in a site-oriented manner (Tf-MSP-AOPB NPs). The preparation conditions were investigated in detail to optimize the Tf binding efficiency. A suitable reaction temperature, time or initial feeding amount could significantly increase the Tf binding amount. The maximum Tf binding amount on the MSP-AOPB NPs was 184 mg g-1, and the targeting ligand density on the surface could be well controlled by simply adjusting the reaction conditions. In vitro studies demonstrated the excellent Tf-mediated targeting ability and enhanced cellular uptake efficacy by varying the ligand density. The optimal ligand binding amount for achieving the highest cellular uptake efficiency was 94 mg Tf/g, which corresponds to a ligand binding density of about 0.05 Tf/nm2, and the binding efficiency of conjugation was higher than 90%. Moreover, Tf-MSP-AOPB NPs prepared by a site-oriented conjugation strategy showed the best cell targeting ability, and their cellular uptake amount was 25 and 127 times higher than that of physical adsorption and EDC/NHS coupling reaction in HepG2 cells, respectively. This study provides a facile site-oriented bioconjugation technique for different kinds of antibodies, and a suitable ligand density can be easily attained to enhance the cellular uptake efficacy, which shows great significance for targeted delivery and cancer therapy.

Glycoproteomic contributions to hepatocellular carcinoma research: a 2023 update

INTRODUCTION

Hepatocellular carcinoma (HCC) represents a significant burden globally, which ranks sixth among the most frequently diagnosed cancers and stands as the third leading cause of cancer-related mortality. Glycoproteomics, as an important branch of proteomics, has already made significant achievements in the field of HCC research. Aberrant protein glycosylation has shown to promote the malignant transformation of hepatocytes by modulating a wide range of tumor-promoting signaling pathways. The glycoproteome provides valuable information for understanding cancer progression, tumor immunity, and clinical outcome, which could serve as potential diagnostic, prognostic, and therapeutic tools in HCC.

AREAS COVERED

In this review, recent advances of glycoproteomics contribute to clinical applications (diagnosis and prognosis) and molecular mechanisms (hepatocarcinogenesis, progression, stemness and recurrence, and drug resistance) of HCC are summarized.

EXPERT OPINION

Glycoproteomics shows promise in HCC, enhancing early detection, risk stratification, and personalized treatments. Challenges include sample heterogeneity, diverse glycans structures, sensitivity issues, complex workflows, limited databases, and incomplete understanding of immune cell glycosylation. Addressing these limitations requires collaborative efforts, technological advancements, standardization, and validation studies. Future research should focus on targeting abnormal protein glycosylation therapeutically. Advancements in glycobiomarkers and glycosylation-targeted therapies will greatly impact HCC diagnosis, prognosis, and treatment.

Identification and targeting of protein tyrosine kinase 7 (PTK7) as an immunotherapy candidate for neuroblastoma

GD2-targeting immunotherapies have improved survival in children with neuroblastoma, yet on-target, off-tumor toxicities can occur and a subset of patients cease to respond. The majority of neuroblastoma patients who receive immunotherapy have been previously treated with cytotoxic chemotherapy, making it paramount to identify neuroblastoma-specific antigens that remain stable throughout standard treatment. Cell surface glycoproteomics performed on human-derived neuroblastoma tumors in mice following chemotherapy treatment identified protein tyrosine kinase 7 (PTK7) to be abundantly expressed. Furthermore, PTK7 shows minimal expression on pediatric-specific normal tissues. We developed an anti-PTK7 chimeric antigen receptor (CAR) and find PTK7 CAR T cells specifically target and kill PTK7-expressing neuroblastoma in vitro. In vivo, human/murine binding PTK7 CAR T cells regress aggressive neuroblastoma metastatic mouse models and prolong survival with no toxicity. Together, these data demonstrate preclinical efficacy and tolerability for targeting PTK7 and support ongoing investigations to optimize PTK7-targeting CAR T cells for neuroblastoma.

Chondroitin 4-O-sulfation regulates hippocampal perineuronal nets and social memory

Glycan alterations are associated with aging, neuropsychiatric, and neurodegenerative diseases, although the contributions of specific glycan structures to emotion and cognitive functions remain largely unknown. Here, we used a combination of chemistry and neurobiology to show that 4-O-sulfated chondroitin sulfate (CS) polysaccharides are critical regulators of perineuronal nets (PNNs) and synapse development in the mouse hippocampus, thereby affecting anxiety and cognitive abilities such as social memory. Brain-specific deletion of CS 4-O-sulfation in mice increased PNN densities in the area CA2 (cornu ammonis 2), leading to imbalanced excitatory-to-inhibitory synaptic ratios, reduced CREB activation, elevated anxiety, and social memory dysfunction. The impairments in PNN densities, CREB activity, and social memory were recapitulated by selective ablation of CS 4-O-sulfation in the CA2 region during adulthood. Notably, enzymatic pruning of the excess PNNs reduced anxiety levels and restored social memory, while chemical manipulation of CS 4-O-sulfation levels reversibly modulated PNN densities surrounding hippocampal neurons and the balance of excitatory and inhibitory synapses. These findings reveal key roles for CS 4-O-sulfation in adult brain plasticity, social memory, and anxiety regulation, and they suggest that targeting CS 4-O-sulfation may represent a strategy to address neuropsychiatric and neurodegenerative diseases associated with social cognitive dysfunction.

Global quantification of newly synthesized proteins reveals cell type- and inhibitor-specific effects on protein synthesis inhibition

Manipulation of protein synthesis is commonly applied to uncover protein functions and cellular activities. Multiple inhibitors with distinct mechanisms have been widely investigated and employed in bio-related research, but it is extraordinarily challenging to measure and evaluate the synthesis inhibition efficiencies of individual proteins by different inhibitors at the proteome level. Newly synthesized proteins are the immediate and direct products of protein synthesis, and thus their comprehensive quantification provides a unique opportunity to study protein inhibition. Here, we systematically investigate protein inhibition and evaluate different popular inhibitors, i.e. cycloheximide, puromycin, and anisomycin, through global quantification of newly synthesized proteins in several types of human cells (A549, MCF-7, Jurkat, and THP-1 cells). The inhibition efficiencies of protein synthesis are comprehensively measured by integrating azidohomoalanine-based protein labeling, selective enrichment, a boosting approach, and multiplexed proteomics. The same inhibitor results in dramatic variation of the synthesis inhibition efficiencies for different proteins in the same cells, and each inhibitor exhibits unique preferences. Besides cell type- and inhibitor-specific effects, some universal rules are unraveled. For instance, nucleolar and ribosomal proteins have relatively higher inhibition efficiencies in every type of cells treated with each inhibitor. Moreover, proteins intrinsically resistant or sensitive to the inhibition are identified and found to have distinct functions. Systematic investigation of protein synthesis inhibition in several types of human cells by different inhibitors provides valuable information about the inhibition of protein synthesis, advancing our understanding of inhibiting protein synthesis.

Sensitive Analysis of Recombinant Human Erythropoietin Glycopeptides by On-Line Phenylboronic Acid Solid-Phase Extraction Capillary Electrophoresis Mass Spectrometry

In this study, several chromatographic sorbents: porous graphitic carbon (PGC), aminopropyl hydrophilic interaction (aminopropyl-HILIC), and phenylboronic acid (PBA) were assessed for the analysis of glycopeptides by on-line solid-phase extraction capillary electrophoresis mass spectrometry (SPE-CE-MS). As the PBA sorbent provided the most promising results, a PBA-SPE-CE-MS method was developed for the selective and sensitive preconcentration of glycopeptides from enzymatic digests of glycoproteins. Recombinant human erythropoietin (rhEPO) was selected as the model glycoprotein and subjected to enzymatic digestion with several proteases. The tryptic O₁₂₆ and N₈₃ glycopeptides from rhEPO were targeted to optimize the methodology. Under the optimized conditions, intraday precision, linearity, limits of detection (LODs), and microcartridge lifetime were evaluated, obtaining improved results compared to that from a previously reported TiO₂-SPE-CE-MS method, especially for LODs of N-glycopeptides (up to 500 times lower than by CE-MS and up to 200 times lower than by TiO₂-SPE-CE-MS). Moreover, rhEPO Glu-C digests were also analyzed by PBA-SPE-CE-MS to better characterize N₂₄ and N₃₈ glycopeptides. Finally, the established method was used to analyze two rhEPO products (EPOCIM and NeuroEPO plus), demonstrating its applicability in biopharmaceutical analysis. The sensitivity of the proposed PBA-SPE-CE-MS method improves the existing CE-MS methodologies for glycopeptide analysis and shows a great potential in glycoprotein analysis to deeply characterize protein glycosites even at low concentrations of the protein digest.

The next "sweet" spot for pancreatic ductal adenocarcinoma: Glycoprotein for early detection

Pancreatic ductal adenocarcinoma (PDAC) is the most common neoplastic disease of the pancreas, accounting for more than 90% of all pancreatic malignancies. As a highly lethal malignancy, PDAC is the fourth leading cause of cancer-related deaths worldwide with a 5-year overall survival of less than 8%. The efficacy and outcome of PDAC treatment largely depend on the stage of disease at the time of diagnosis. Surgical resection followed by adjuvant chemotherapy remains the only possibly curative therapy, yet 80%-90% of PDAC patients present with nonresectable PDAC stages at the time of clinical presentation. Despite our advancing knowledge of PDAC, the prognosis remains strikingly poor, which is primarily due to the difficulty of diagnosing PDAC at the early stages. Recent advances in glycoproteomics and glycomics based on mass spectrometry have shown that aberrations in protein glycosylation plays a critical role in carcinogenesis, tumor progression, metastasis, chemoresistance, and immuno-response of PDAC and other types of cancers. A growing interest has thus been placed upon protein glycosylation as a potential early detection biomarker for PDAC. We herein take stock of the advancements in the early detection of PDAC that were carried out with mass spectrometry, with special focus on protein glycosylation.

Systematic characterization of extracellular glycoproteins using mass spectrometry

Surface and secreted glycoproteins are essential to cells and regulate many extracellular events. Because of the diversity of glycans, the low abundance of many glycoproteins, and the complexity of biological samples, a system-wide investigation of extracellular glycoproteins is a daunting task. With the development of modern mass spectrometry (MS)-based proteomics, comprehensive analysis of different protein modifications including glycosylation has advanced dramatically. This review focuses on the investigation of extracellular glycoproteins using MS-based proteomics. We first discuss the methods for selectively enriching surface glycoproteins and investigating protein interactions on the cell surface, followed by the application of MS-based proteomics for surface glycoprotein dynamics analysis and biomarker discovery. We then summarize the methods to comprehensively study secreted glycoproteins by integrating various enrichment approaches with MS-based proteomics and their applications for global analysis of secreted glycoproteins in different biological samples. Collectively, MS significantly expands our knowledge of extracellular glycoproteins and enables us to identify extracellular glycoproteins as potential biomarkers for disease detection and drug targets for disease treatment.

Methods for quantification of glycopeptides by liquid separation and mass spectrometry

Recent advances in analytical techniques provide the opportunity to quantify even low-abundance glycopeptides derived from complex biological mixtures, allowing for the identification of glycosylation differences between healthy samples and those derived from disease states. Herein, we discuss the sample preparation procedures and the mass spectrometry (MS) strategies that have facilitated glycopeptide quantification, as well as the standards used for glycopeptide quantification. For sample preparation, various glycopeptide enrichment methods are summarized including the columns used for glycopeptide separation in liquid chromatography separation. For MS analysis strategies, MS1 level-based quantification and MS2 level-based quantification are described, either with or without labeling, where we have covered isotope labeling, TMT/iTRAQ labeling, data dependent acquisition, data independent acquisition, multiple reaction monitoring, and parallel reaction monitoring. The strengths and weaknesses of these methods are compared, particularly those associated with the figures of merit that are important for clinical biomarker studies and the pathological and functional studies of glycoproteins in various diseases. Possible future developments for glycopeptide quantification are discussed.

Glycan-selective in-situ growth of thermoresponsive polymers for thermoprecipitation and enrichment of N-glycoprotein/glycopeptides

In view of the biological significance and micro-heterogeneity of protein glycosylation for human health, specific enrichment of N-glycosylated proteins/peptides from complex biological samples is a prerequisite for the discovery of disease biomarkers and clinical diagnosis. In this work, we propose a "grafting-from" N-glycoprotein enriching method based on the in-situ growth of thermoresponsive polymer brushes from the N-glycosylated site of proteins. The initiator was first attached to the pre-oxidized glycan moieties by hydrazide chemistry, from which the thermoresponsive polymers can be grown to form giant protein-polymer conjugates (PPC). The thermosensitive PPC can be precipitated and separated by raising the temperature to above its lower critical solubility temperature (LCST). Mass spectrometry verified 210 N-glycopeptides corresponding to 136 N-glycoproteins in the rabbit serum. These results demonstrate the capability of the tandem thermoprecipitation strategy to enrich and separate N-glycoprotein/glycopeptide. Due to its simplicity and efficiency specifically, this method holds the potential for identifying biomarkers from biological samples in N-glycoproteome analysis.

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.

Preparation of tannic acid and L-cysteine functionalized magnetic composites for synergistic enrichment of N-glycopeptides followed by mass spectrometric analysis

Glycoprotein is involved in a variety of biological activities and has been linked to a number of diseases. Glycopeptide enrichment prior to mass spectrometry (MS) detection is crucial to reduce interference, improve detection efficiency, and analyze proteomics deeply and comprehensively. Here, we prepared a novel magnetic hydrophilic material combining tannic acid (TA) and L-cysteine (L-Cys) through a simple and fast procedure. Owing to the synergistic hydrophilic interaction of TA and L-Cys, the obtained adsorbent material shows excellent enrichment performance toward N-glycopeptides with low detection limit, high selectivity, and good reusability. Besides, the material can also be utilized for the enrichment of N-glycopeptides in human serum and saliva, which shows its application prospect in complex biological samples.

Mass spectrometry-based N-glycosylation analysis in kidney disease

Kidney disease is a global health concern with an enormous expense. It is estimated that more than 10% of the population worldwide is affected by kidney disease and millions of patients would progress to death prematurely and unnecessarily. Although creatinine detection and renal biopsy are well-established tools for kidney disease diagnosis, they are limited by several inevitable defects. Therefore, diagnostic tools need to be upgraded, especially for the early stage of the disease and possible progression. As one of the most common post-translational modifications of proteins, N-glycosylation plays a vital role in renal structure and function. Deepening research on N-glycosylation in kidney disease provides new insights into the pathophysiology and paves the way for clinical application. In this study, we reviewed recent N-glycosylation studies on several kidney diseases. We also summarized the development of mass spectrometric methods in the field of N-glycoproteomics and N-glycomics.

Optimized Glycopeptide Enrichment Method-It Is All about the Sauce

Protein glycosylation is a family of posttranslational modifications that play a crucial role in many biological pathways and diseases. The enrichment and analysis of such a diverse family of modifications are very challenging because of the number of possible glycan–peptide combinations. Among the methods used for the enrichment of glycopeptides, boronic acid never lived up to its promise. While most studies focused on improving the affinity of the boronic acids to the sugars, we discovered that the buffer choice is just as important for successful enrichment if not more so. We show that an amine-less buffer allows for the best glycoproteomic coverage, in human plasma and brain specimens, improving total quantified glycopeptides by over 10-fold, and reaching 1598 N-linked glycopeptides in the brain and 737 in nondepleted plasma. We speculate that amines compete with the glycans for boronic acid binding, and therefore the elimination of them improved the method significantly.

Aberrant Fucosylation of Saliva Glycoprotein Defining Lung Adenocarcinomas Malignancy

Aberrant glycosylation is a hallmark of cancer found during tumorigenesis and tumor progression. Lung cancer (LC) induced by oncogene mutations has been detected in the patient's saliva, and saliva glycosylation has been altered. Saliva contains highly glycosylated glycoproteins, the characteristics of which may be related to various diseases. Therefore, elucidating cancer-specific glycosylation in the saliva of healthy, non-cancer, and cancer patients can reveal whether tumor glycosylation has unique characteristics for early diagnosis. In this work, we used a solid-phase chemoenzymatic method to study the glycosylation of saliva glycoproteins in clinical specimens. The results showed that the α1,6-core fucosylation of glycoproteins was increased in cancer patients, whereas α1,2 or α1,3 fucosylation was significantly increased. We further analyzed the expression of fucosyltransferases responsible for α1,2, α1,3, and α1,6 fucosylation. The fucosylation of the saliva of cancer patients is drastically different from that of non-cancer or health controls. These results indicate that the glycoform of saliva fucosylation distinguishes LC from other diseases, and this feature has the potential to diagnose lung adenocarcinoma.

Lamprey immunity protein enables detection for bladder cancer through recognizing N-hydroxyacetylneuraminic acid (Neu5Gc)-modified as a diagnostic marker and exploration of its production mechanism

Previous studies have demonstrated that Neu5Gc is highly expressed in breast, ovarian, prostate, colon and lung cancers, but not in normal human cells. The presence of Neu5Gc is important for prognosis and is associated with aggressiveness, metastasis, and tumor grade. However, increased Neu5Gc in bladder cancer remains unclear. LIP from lamprey binds the carbohydrate receptor of N-glycolylneuraminic acid (Neu5Gc). The combination of Neu5Gc and LIP suggested that it might be used as a diagnostic tool for the detection of Neu5Gc tumor antigen. Here, the classical animal model of bladder cancer was successfully induced by MNU bladder perfusion. The ELISA results showed that the expression level of Neu5Gc in the urine of normal rats was 94.96 ± 21.01ng/mg, and that of bladder cancer rats was 158.28 ± 34.86 ng/mg. In addition, the results of SNA and LIP immunohistochemistry demonstrated the high expression of Neu5Gc in bladder cancer. After the addition of Neu5Gc to BIU-87 and SV-HUC-1 cells, transcriptomic sequencing and real-time quantitative PCR analysis demonstrated that the gene expression of Neu5Gc synthesis pathway was significantly increased. These data suggest that LIP provides a new tool for the detection of biological samples, especially urine from patients with bladder cancer or suspected cancer, and that revealing the mechanism of abnormal glycosylation can provide theoretical basis for clinical studies.

Recent advancements in glycoproteomic studies: Glycopeptide enrichment and derivatization, characterization of glycosylation in SARS CoV2, and interacting glycoproteins

Proteomics studies allow for the determination of the identity, amount, and interactions of proteins under specific conditions that allow the biological state of an organism to ultimately change. These conditions can be either beneficial or detrimental. Diseases are due to detrimental changes caused by either protein overexpression or underexpression caused by as a result of a mutation or posttranslational modifications (PTM), among other factors. Identification of disease biomarkers through proteomics can be potentially used as clinical information for diagnostics. Common biomarkers to look for include PTM. For example, aberrant glycosylation of proteins is a common marker and will be a focus of interest in this review. A common way to analyze glycoproteins is by glycoproteomics involving mass spectrometry. Due to factors such as micro- and macroheterogeneity which result in a lower abundance of each version of a glycoprotein, it is difficult to obtain meaningful results unless rigorous sample preparation procedures are in place. Microheterogeneity represents the diversity of glycans at a single site, whereas macroheterogeneity depicts glycosylation levels at each site of a protein. Enrichment and derivatization of glycopeptides help to overcome these limitations. Over the time range of 2016 to 2020, several methods have been proposed in the literature and have contributed to drastically improve the outcome of glycosylation analysis, as presented in the sampling surveyed in this review. As a current topic in 2020, glycoproteins carried by pathogens can also cause disease and this is seen with SARS CoV2, causing the COVID-19 pandemic. This review will discuss glycoproteomic studies of the spike glycoprotein and interacting proteins such as the ACE2 receptor.

Nanopore-Based Single-Entity Electrochemistry for the Label-Free Monitoring of Single-Molecule Glycoprotein-Boronate Affinity Interaction and Its Sensing Application

Nanopipettes provide a promising confined space that enables advances in single-molecule analysis, and their unique conical tubular structure is also suitable for single-cell analysis. In this work, functionalized-nanopore-based single-entity electrochemistry (SEE) analysis tools were developed for the label-free monitoring of single-molecule glycoprotein-boronate affinity interaction for the first time, and immunoglobulin G (IgG, one of the important biomarkers for many diseases such as COVID-19 and cancers) was employed as the model glycoprotein. The principle of this method is based on a single glycoprotein molecule passing through 4-mercaptophenylboronic acid (4-MPBA)-modified nanopipettes under a bias voltage and in the meantime interacting with the boronate group from modified 4-MPBA. This translocation and affinity interaction process can generate distinguishable current blockade signals. Based on the statistical analysis of these signals, the equilibrium association constant (κ_a) of single-molecule glycoprotein-boronate affinity interaction was obtained. The results show that the κ_a of IgG in the confined nanopore at the single-molecule level is much larger than that measured in the open system at the ensemble level, which is possibly due to the enhanced multivalent synergistic binding in the restricted space. Moreover, the functionalized-nanopore-based SEE analysis tools were further applied for the label-free detection of IgG, and the results indicate that our method has potential application value for the detection of glycoproteins in real samples, which also paves way for the single-cell analysis of glycoproteins.

Simultaneously Identifying and Distinguishing Glycoproteins with O-GlcNAc and O-GalNAc (the Tn Antigen) in Human Cancer Cells

Glycoproteins with diverse glycans are essential to human cells, and subtle differences in glycan structures may result in entirely different functions. One typical example is proteins modified with O-linked β-N-acetylglucosamine (O-GlcNAc) and O-linked α-N-acetylgalactosamine (O-GalNAc) (the Tn antigen), in which the two glycans have very similar structures and identical chemical compositions, making them extraordinarily challenging to be distinguished. Here, we developed an effective method benefiting from selective enrichment and the enzymatic specificity to simultaneously identify and distinguish glycoproteins with O-GlcNAc and O-GalNAc. Metabolic labeling was combined with bioorthogonal chemistry for enriching glycoproteins modified with O-GlcNAc and O-GalNAc. Then, the enzymatic reaction with galactose oxidase was utilized to specifically oxidize O-GalNAc, but not O-GlcNAc, generating the different tags between glycopeptides with O-GlcNAc and O-GalNAc that can be easily distinguishable by mass spectrometry (MS). Among O-GlcNAcylated proteins commonly identified in three types of human cells, those related to transcription and RNA binding are highly enriched. Cell-specific features are also revealed. Among glycoproteins exclusively in Jurkat cells, those involved in human T-lymphotropic virus type 1 (HTLV-1) infection are overrepresented, which is consistent with the cell line source and suggests that protein O-GlcNAcylation participated in the response to the virus infection. Furthermore, glycoproteins with the Tn antigen have different subcellular distributions in different cells, which may be attributed to the distinct mechanisms for the formation of protein O-GalNAcylation.

Glycomic and Glycoproteomic Techniques in Neurodegenerative Disorders and Neurotrauma: Towards Personalized Markers

The proteome represents all the proteins expressed by a genome, a cell, a tissue, or an organism at any given time under defined physiological or pathological circumstances. Proteomic analysis has provided unparalleled opportunities for the discovery of expression patterns of proteins in a biological system, yielding precise and inclusive data about the system. Advances in the proteomics field opened the door to wider knowledge of the mechanisms underlying various post-translational modifications (PTMs) of proteins, including glycosylation. As of yet, the role of most of these PTMs remains unidentified. In this state-of-the-art review, we present a synopsis of glycosylation processes and the pathophysiological conditions that might ensue secondary to glycosylation shortcomings. The dynamics of protein glycosylation, a crucial mechanism that allows gene and pathway regulation, is described. We also explain how-at a biomolecular level-mutations in glycosylation-related genes may lead to neuropsychiatric manifestations and neurodegenerative disorders. We then analyze the shortcomings of glycoproteomic studies, putting into perspective their downfalls and the different advanced enrichment techniques that emanated to overcome some of these challenges. Furthermore, we summarize studies tackling the association between glycosylation and neuropsychiatric disorders and explore glycoproteomic changes in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington disease, multiple sclerosis, and amyotrophic lateral sclerosis. We finally conclude with the role of glycomics in the area of traumatic brain injury (TBI) and provide perspectives on the clinical application of glycoproteomics as potential diagnostic tools and their application in personalized medicine.

Veni, Vidi, Vici: Immobilized Peptide-Based Conjugates as Tools for Capture, Analysis, and Transformation

Analysis of peptide biomarkers of pathological states of the organism is often a serious challenge, due to a very complex composition of the cell and insufficient sensitivity of the current analytical methods (including mass spectrometry). One of the possible ways to overcome this problem is sample enrichment by capturing the selected components using a specific solid support. Another option is increasing the detectability of the desired compound by its selective tagging. Appropriately modified and immobilized peptides can be used for these purposes. In addition, they find application in studying the specificity and activity of proteolytic enzymes. Immobilized heterocyclic peptide conjugates may serve as metal ligands, to form complexes used as catalysts or analytical markers. In this review, we describe various applications of immobilized peptides, including selective capturing of cysteine-containing peptides, tagging of the carbonyl compounds to increase the sensitivity of their detection, enrichment of biological samples in deoxyfructosylated peptides, and fishing out of tyrosine–containing peptides by the formation of azo bond. Moreover, the use of the one-bead-one-compound peptide library for the analysis of substrate specificity and activity of caspases is described. Furthermore, the evolution of immobilization from the solid support used in peptide synthesis to nanocarriers is presented. Taken together, the examples presented here demonstrate immobilized peptides as a multifunctional tool, which can be successfully used to solve multiple analytical problems.

Preparation of a boronate affinity-functionalized metal–organic framework material for selective recognition and separation of glycoproteins at physiological pH

A boronate affinity functionalized metal–organic framework material was successfully prepared for the efficient and selective extraction of OVA glycoprotein from egg white samples and protein powder.

Maximizing Depth of PTM Coverage: Generating Robust MS Datasets for Computational Prediction Modeling

Post-translational modifications (PTMs) regulate complex biological processes through the modulation of protein activity, stability, and localization. Insights into the specific modification type and localization within a protein sequence can help ascertain functional significance. Computational models are increasingly demonstrated to offer a low-cost, high-throughput method for comprehensive PTM predictions. Algorithms are optimized using existing experimental PTM data, thus accurate prediction performance relies on the creation of robust datasets. Herein, advancements in mass spectrometry-based proteomics technologies to maximize PTM coverage are reviewed. Further, requisite experimental validation approaches for PTM predictions are explored to ensure that follow-up mechanistic studies are focused on accurate modification sites.

Method for Identifying Galectin Ligands on Lymphocyte Membrane Glycoproteins

Glycosylation is one of the most common protein posttranslational modifications. Most human lymphocyte membrane receptors are modified by diverse glycan structures, and functional studies have indicated that a family of glycan-binding proteins, galectins, can significantly modulate lymphocyte development and function by interacting with these glycans. Several galectins have a varying degree of affinity for the N-acetyllactosamine (LacNAc) disaccharide, and some critical lymphocyte receptors can be modified by glycan structures carrying this motif. However, the site-specific glycan composition on primary lymphocyte membrane receptors in healthy individuals is largely limited. The main reason for the limitation is low abundance of available material from a single donor and compositional heterogeneity in glycan structures that can potentially modify a protein. Donor-dependent variability in N-glycan structures on CD16a isolated from primary NK cells of healthy human donors was recently reported. NK cell CD16a is glycosylated at five N-glycosylation sites, and two of the five sites are modified, almost exclusively, by N-glycans with multiple LacNAc repeats which can serve as ligands for endogenous galectins. Thus, the protocol described in this section can be utilized to identify galectin ligands at specific glycosylation sites of endogenous membrane receptor from circulating primary human lymphocytes.

Abnormal sialylation and fucosylation of saliva glycoproteins: Characteristics of lung cancer-specific biomarkers

Dysregulated surface glycoproteins play an important role in tumor cell proliferation and progression. Abnormal glycosylation of these glycoproteins may activate tumor signal transduction and lead to tumor development. The tumor microenvironment alters its molecular composition, some of which regulate protein glycosylation biosynthesis. The glycosylation of saliva proteins in lung cancer patients is different from healthy controls, in which the glycans of cancer patients are highly sialylated and hyperfucosylated. Most studies have shown that O-glycans from cancer are truncated O-glycans, while N-glycans contain fucoses and sialic acids. Because glycosylation analysis is challenging, there are few reports on how glycosylation of saliva proteins is related to the occurrence or progression of lung cancer. In this review, we discussed glycoenzymes involved in protein glycosylation, their changes in tumor microenvironment, potential tumor biomarkers present in body fluids, and abnormal glycosylation of saliva or lung glycoproteins. We further explored the effect of glycosylation changes on tumor signal transduction, and emphasized the role of receptor tyrosine kinases in tumorigenesis and metastasis.

Advances in mass spectrometry-based glycoproteomics: An update covering the period 2017-2021

Protein glycosylation is one of the most common posttranslational modifications, and plays an essential role in a wide range of biological processes such as immune response, intercellular signaling, inflammation, host-pathogen interaction, and protein stability. Glycoproteomics is a proteomics subfield dedicated to identifying and characterizing the glycans and glycoproteins in a given cell or tissue. Aberrant glycosylation has been associated with various diseases such as Alzheimer's disease, viral infections, inflammation, immune deficiencies, congenital disorders, and cancers. However, glycoproteomic analysis remains challenging because of the low abundance, site-specific heterogeneity, and poor ionization efficiency of glycopeptides during LC-MS analyses. Therefore, the development of sensitive and accurate approaches to efficiently characterize protein glycosylation is crucial. Methods such as metabolic labeling, enrichment, and derivatization of glycopeptides, coupled with different mass spectrometry techniques and bioinformatics tools, have been developed to achieve sophisticated levels of quantitative and qualitative analyses of glycoproteins. This review attempts to update the recent developments in the field of glycoproteomics reported between 2017 and 2021.

[Preparation of multi-functional magnetic nanoparticles for harvesting low-molecular-weight glycoproteins]

低分子量糖蛋白被认为是发现疾病生物标志物的宝库。特异性的萃取吸附剂对这一类化合物的萃取和富集是必不可少的。硼亲和材料在近年来取得了很大的发展,但专门用于选择性富集低分子量糖蛋白的硼亲和材料目前鲜有报道。该文提出了具有多种功能的磁性纳米颗粒(MNPs),用于低分子量糖蛋白的选择性捕获。该多功能磁性纳米颗粒是用硼酸功能化聚合物网络包裹的磁性纳米复合物。该多功能磁性纳米材料是利用磁性的纳米颗粒内核通过在其表面修饰苯硼酸功能团的聚丙烯酸高分子网络链制备得到。该材料不仅具有常规磁性材料在磁分离方面的基本优势,还能提供三重预先设计的先进功能:1)尺寸排阻效应,去除高分子量蛋白质的干扰;2)对低分子量糖蛋白的选择性萃取;3)保护捕获到的低分子量糖蛋白不被降解和污染。该材料的选择性萃取功能来自于硼酸配基与糖蛋白的顺式二醇部分的亲和性,而尺寸限制效应和保护功能则依赖于磁性纳米颗粒表面修饰的聚合物网络,允许低分子量化合物选择性通过。通过实验验证了这些预设的功能,且通过改变聚合物链长可以调节限径效应的阈值。这种多功能磁性纳米复合物可以进一步发展成有前景的纳米探针,不仅可以选择性捕获低分子量糖蛋白,还可以选择性捕获核苷和聚糖等其他具有重要生物学意义的顺式二醇分子。因此,该文报道的材料制备策略为从复杂样品中选择性萃取靶标化合物的多功能吸附剂的设计和合成提供了新思路。

[Recent advances in glycopeptide enrichment and mass spectrometry data interpretation approaches for glycoproteomics analyses]

蛋白质糖基化是生物体内最重要的翻译后修饰之一,在蛋白质稳定性、细胞内和细胞间信号转导、激素活化或失活和免疫调节等生理过程和病理进程中发挥重要作用。而异常的蛋白质糖基化往往和多种疾病的发生发展密切相关,目前应用于临床检测的多种肿瘤生物标志物大多属于糖蛋白或者糖抗原。因此在组学层次系统分析蛋白质糖基化的变化对阐明生物体内糖基化修饰的调控机理和发现新型疾病标志物都非常重要。基于质谱的蛋白质组学技术为全面分析蛋白质及其修饰提供了有效的分析手段。在自下而上的蛋白质组学研究中,由于完整糖基化肽段同时存在性质各异的肽段骨架和糖链结构、糖肽的相对丰度和离子化效率较低以及糖基化修饰有高度异质性等特点,完整糖肽的分析比其他翻译后修饰更加困难。近年来,为了更全面、系统地分析蛋白质糖基化,研究人员发展了一些新技术,包括完整糖肽的富集技术、质谱的碎裂模式和数据采集模式、质谱数据的解析方法和定量策略等等,大力推进了该领域的研究水平,也为研究蛋白质糖基化相关的生物标志物提供了技术支持。该篇综述主要关注近年来基于质谱的糖蛋白质组学研究中的新进展,重点介绍针对完整N-和O-糖基化肽段的富集新技术和谱图解析新方法,并讨论其在肿瘤早期诊断方面的应用潜力。

[Recent advances in functionalized magnetic nanomaterials for glycoprotein and glycopeptide enrichment]

蛋白质糖基化作为最重要的翻译后修饰之一,在生物体诸如细胞信号转导、蛋白质翻译调控、免疫应答等诸多生命过程中发挥重要作用。此外,蛋白质的异常糖基化还与肿瘤等疾病的发生发展密切相关,这为以糖蛋白为目标的疾病生物标志物的发现提供了可能。尽管质谱已经成为糖蛋白质组学的重要分析工具,但糖肽的低丰度和低电离效率使得其直接质谱分析仍面临挑战。在糖蛋白质组学研究中,从复杂的生物样品中富集糖蛋白和糖肽是重要的环节。磁性固相萃取(MSPE)是一种操作简单、成本低和萃取效率高的样品预处理方法。在磁性固相萃取中,磁性吸附剂是影响萃取效果的关键,将功能化磁性纳米材料作为吸附剂进行糖蛋白质组学研究已经得到广泛应用。该文综述了糖分子、离子液体、凝集素、硼酸亲和配体、金属有机框架、共价有机骨架等功能化磁性纳米材料的制备及其在糖蛋白及糖肽富集中的应用。上述功能化磁性纳米材料具有高比表面积、大量作用位点等特点,其富集机理包括亲水相互作用色谱、凝集素亲和作用色谱、硼酸化学法和肼化学法等,主要应用于血清、血浆、细胞、组织、唾液等样品的糖蛋白和糖肽的富集。该文引用了近十年来发表的约90篇源于科学引文索引(SCI)与中文核心期刊的相关论文,并于文末对磁性纳米材料在糖蛋白和糖肽富集领域的发展趋势进行了展望。

Peptide and protein assays using customizable bio-affinity arrays combined with ambient ionization mass spectrometry

High-throughput identification and quantification of protein/peptide biomarkers from biofluids in a label-free manner is achieved by interfacing bio-affinity arrays (BAAs) with nano-electrospray desorption electrospray ionization mass spectrometry (nano-DESI-MS). A wide spectrum of proteins and peptides ranging from phosphopeptides to cis-diol biomolecules as well as thrombin can be rapidly extracted via arbitrarily predefined affinity interactions including coordination chemistry, covalent bonding, and biological recognition. An integrated MS platform allows continuous interrogation. Profiling and quantitation of dysregulated phosphopeptides from small-volume (∼5 μL) serum samples has been successfully demonstrated. As a front-end device adapted to any mass spectrometer, this MS platform might hold much promise in protein/peptide analysis in point-of-care (POC) diagnostics and clinical applications.

Customizable bio-affinity arrays were interfaced with ambient ionization mass spectrometry for high-throughput assays of protein/peptide biomarkers in biofluids.