Advancing MSn spatial resolution and documentation for glycosaminoglycans by sulfate-isotope exchange

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

State-of-the-art glycosaminoglycan characterization

Glycosaminoglycans (GAGs) are heterogeneous acidic polysaccharides involved in a range of biological functions. They have a significant influence on the regulation of cellular processes and the development of various diseases and infections. To fully understand the functional roles that GAGs play in mammalian systems, including disease processes, it is essential to understand their structural features. Despite having a linear structure and a repetitive disaccharide backbone, their structural analysis is challenging and requires elaborate preparative and analytical techniques. In particular, the extent to which GAGs are sulfated, as well as variation in sulfate position across the entire oligosaccharide or on individual monosaccharides, represents a major obstacle. Here, we summarize the current state-of-the-art methodologies used for GAG sample preparation and analysis, discussing in detail liquid chromatograpy and mass spectrometry-based approaches, including advanced ion activation methods, ion mobility separations and infrared action spectroscopy of mass-selected species.

Commercial Low Molecular Weight Heparins - Patent Ecosystem and Technology Paradigm for Quality Characterization

Heparin is a subject of ever-growing interest for laboratory researchers and pharmaceutical industry. One of the driving factors is its critical life-saving drug status, which during the COVID-19 pandemic has assumed a central role in disease treatment and/or prevention. Apart, heparin is one amongst few drugs enjoying a "demand constant" status. In 2020, heparin market size was valued to US$6.5 bn., and given the ongoing stability in the COVID-19 health crisis, it is expected to reach US$11.43 bn. by 2027 with yearly growth rate momentum (CAGR) of 3.9% during the forecast period (Pepi et al., Mol Cell Proteomics 20:100,025, 2021). As patent is a limited monopoly, every year, many patents on low molecular weight heparin (LMWH; a chemically or enzymatically degraded product of unfractionated heparin) are losing market exclusivity worldwide, inviting the generic/biosimilar drug manufacturers to capture market share with cheaper drug products. By tracking patent expiration, drugs in patent litigation, regulatory setbacks for innovator companies (such as those seeking data exclusivity or patent term extension), or other unexpected events affecting market demand and competition, generics can make investment decisions in manufacturing off-patent LMWH drug products of commercial significance. However, given the US Food and Drug Administration (FDA), European Medicine Agency (EMA), Drug Regulatory Authority of Pakistan (DRAP), and other regulatory authorities scientifically rigorous standards for generic/biosimilar LMWH drug products marketing approval, the market is secured and momentous for drug makers that could demonstrate through scientific and clinical dataset that the generic/biosimilar LMWH drug product is of the same quality and purity as the innovator drug product. This study presents an overview of the patent landscape of commercially available LMWHs and advanced analytical techniques for their structural and biochemical characterization for quality control and quality assurance during manufacturing and post-marketing. The study also covers FDA, EMA, Health Canada, and DRAP's current approaches to evaluating the generic/biosimilar LMWH drug products for quality, safety including immunogenicity, and efficacy.

Developments in Mass Spectrometry for Glycosaminoglycan Analysis: A Review

This review covers recent developments in glycosaminoglycan (GAG) analysis via mass spectrometry (MS). GAGs participate in a variety of biological functions, including cellular communication, wound healing, and anticoagulation, and are important targets for structural characterization. GAGs exhibit a diverse range of structural features due to the variety of O- and N-sulfation modifications and uronic acid C-5 epimerization that can occur, making their analysis a challenging target. Mass spectrometry approaches to the structure assignment of GAGs have been widely investigated, and new methodologies remain the subject of development. Advances in sample preparation, tandem MS techniques (MS/MS), online separations, and automated analysis software have advanced the field of GAG analysis. These recent developments have led to remarkable improvements in the precision and time efficiency for the structural characterization of GAGs.

Peracylation Coupled with Tandem Mass Spectrometry for Structural Sequencing of Sulfated Glycosaminoglycan Mixtures without Depolymerization

The structures of glycosaminoglycans (GAGs), especially the patterns of modification, are crucial to modulate interactions with various protein targets. It is very challenging to determine the fine structures using liquid chromatography-mass spectrometry (LC-MS) due in large part to the gas-phase sulfate losses upon collisional activation. Previously, our group reported a method for fine structure analysis that required permethylation of the GAG oligosaccharide. However, uncontrolled depolymerization during the permethylation process due to esterification of uronic acid lowers the reliability of the method to resolve structures of GAGs, especially for larger oligosaccharides. Here, we describe a simplified derivatization method using propionylation and desulfation. The oligosaccharides have all hydroxyl and amine groups protected with propionyl groups and then have sulfate groups removed to generate unprotected hydroxyl and amine groups at all sites that were previously sulfated. This derivatized oligosaccharide generates informative fragments during collision-induced dissociation that resolve the original sulfation patterns. This method is demonstrated to enable accurate determination of sulfation patterns of even the highly sulfated pentasaccharide fondaparinux by MS² and MS³. Using a mixture of dp6 from porcine heparin, we demonstrate that this method allows for structural characterization of complex mixtures, including clear chromatographic separation and sequencing of structural isomers, all at high yields without evidence of depolymerization. This represents a marked improvement in the reliability to structurally characterize GAG oligosaccharides over permethylation-based derivatization schemes.

Strategy for Isolation, Preparation, and Structural Analysis of Chondroitin Sulfate Oligosaccharides from Natural Sources

The structure of chondroitin sulfate oligosaccharides (CSOs), especially their sulfation pattern, has been found to be closely related with many biological pathways and diseases. However, detailed functional analysis such as their interaction with glycan binding proteins (GBPs) has been lagging, presumably due to the unavailability of well-defined, diverse structures. Besides challenging chemical and enzymatic synthesis, this is also due to the challenges in their purification at the isomer level and structural analysis owing to their instability, structural complexity, and low mass spectrometry detection sensitivity. Herein, we first used recycling preparative HPLC to separate and purify shark CS tetrasaccharide component labeled by a bifunctional fluorescent linker 2-amino-N-(2-aminoethyl)benzamide (AEAB) at the isomer level. Then, each isomer was derivatized through a multistage procedure including N-acetylation, carboxyl amidation, permethylation, and desulfation with silylating reagent. Structural analysis of each derivatized isomer was performed with ESI-MSⁿ in positive ion mode. A total of 16 isomers of CSO-AEAB were isolated, with a minimum mass component of 0.007 mg and a maximum mass component of 17.53 mg, of which 10 isomers (>90 μg) were structurally analyzed. This preparation and structure analysis of CSOs lay the foundation for further study of the structure-activity relationship of CSOs.