A cross-linked polymer possessing a high density of hydrazide groups: high-throughput glycan purification and labeling for high-performance liquid chromatography analysis

A Tag-Free Platform for Synthesis and Screening of Cyclic Peptide Libraries

In the realm of high-throughput screening (HTS), macrocyclic peptide libraries traditionally necessitate decoding tags, essential for both library synthesis and identifying hit peptide sequences post-screening. Our innovation introduces a tag-free technology platform for synthesizing cyclic peptide libraries in solution and facilitates screening against biological targets to identify peptide binders through unconventional intramolecular CyClick and DeClick chemistries (CCDC) discovered through our research. This combination allows for the synthesis of diverse cyclic peptide libraries, the incorporation of various amino acids, and facile linearization and decoding of cyclic peptide binder sequences. Our sensitivity-enhancing derivatization method, utilized in tandem with nano LC-MS/MS, enables the sequencing of peptides even at exceedingly low picomolar concentrations. Employing our technology platform, we have successfully unearthed novel cyclic peptide binders against a monoclonal antibody and the first cyclic peptide binder of HIV capsid protein responsible for viral infections as validated by microscale thermal shift assays (TSA), biolayer interferometry (BLI) and functional assays.

A Versatile Urea Type Linker for Functionalizing Natural Glycans and Its Validation in Glycan Arrays

The isolation from organisms and readily available glycoproteins has become an increasingly convenient source of N-glycans for multiple applications including glycan microarrays, as reference standards in glycan analysis or as reagents that improve bioavailability of protein and peptide therapeutics through conjugation. A problematic step in the isolation process on a preparative scale can be the attachment of a linker for the improved purification, separation, immobilization and quantification of the glycan structures. Addressing this issue, we firstly aimed for the development of an UV active linker for a fast and reliable attachment to anomeric glycosylamines via urea bond formation. Secondly, we validated the new linker on glycan arrays in a comparative study with a collection of N-glycans which were screened against various lectins. In total, we coupled four structurally varied N-glycans to four different linkers, immobilized all constructs on a microarray and compared their binding affinities to four plant and fungal lectins of widely described specificity. Our study shows that the urea type linker showed an overall superior performance for lectin binding and once more, highlights the often neglected influence of the choice of linker on lectin recognition.

Resin and Magnetic Nanoparticle-Based Free Radical Probes for Glycan Capture, Isolation, and Structural Characterization

By combining the merits of solid supports and free radical activated glycan sequencing (FRAGS) reagents, we develop a multifunctional solid-supported free radical probe (SS-FRAGS) that enables glycan enrichment and characterization. SS-FRAGS comprises a solid support, free radical precursor, disulfide bond, pyridyl, and hydrazine moieties. Thio-activated resin and magnetic nanoparticles (MNPs) are chosen as the solid support to selectively capture free glycans via the hydrazine moiety, allowing for their enrichment and isolation. The disulfide bond acts as a temporary covalent linkage between the solid support and the captured glycan, allowing the release of glycans via the cleavage of the disulfide bond by dithiothreitol. The basic pyridyl functional group provides a site for the formation of a fixed charge, enabling detection by mass spectrometry and avoiding glycan rearrangement during collisional activation. The free radical precursor generates a nascent free radical upon collisional activation and thus simultaneously induces systematic and predictable fragmentation for glycan structure elucidation. A radical-driven glycan deconstruction diagram (R-DECON) is developed to visually summarize the MS² results and thus allow for the assembly of the glycan skeleton, making the differentiation of isobaric glycan isomers unambiguous. For application to a real-world sample, we demonstrate the efficacy of the SS-FRAGS by analyzing glycan structures enzymatically cleaved from RNase-B.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Ultrahigh throughput, ultrafiltration-based n-glycomics platform for ultraperformance liquid chromatography (ULTRA(3))

Accurate, reproducible, and fast quantification of N-glycans is crucial not only for the development and quality control of modern glycosylated biopharmaceuticals, but also in clinical biomarker discovery. Several methods exist for fluorescent labeling of N-glycans and subsequent chromatographic separation and quantification. However, the methods can be complex, lengthy, and expensive. Here we report an automated ultrafiltration-based N-glycoanalytical workflow combined with a glycan labeling strategy that is based on the reaction of glycosylamines with fluorescent carbamate. The entire protocol is quick, simple, and cost-effective and requires less than 1 μg of protein per sample. As many as 768 affinity purified IgG glycoprotein samples can be prepared in a single run with a liquid handling platform.

Rapid and high-throughput N-glycomic analysis of plant glycoproteins

Glycoprotein is a major element in higher organisms including mammalians and plants. It is widely accepted that variation in cellular N-glycome is related to modulation in dynamic cellular mechanisms such as cell-cell adhesion, cell activation, and malignant alterations in mammalian cells. However, the physiological importance of glycan modification of glycoproteins in plant cells is still a matter of dispute. Therefore, a comprehensive and high-throughput analysis of N-glycome in plant glycoproteins is needed. Here, an application of the glycoblotting-mass spectrometry technique to plant glycoprotein research is described.

Sulfonyl hydrazine-functionalized polymer as a specific capturer of reducing glycans from complex samples for high-throughput analysis by electrospray ionization mass spectrometry

Qualitative and quantitative studies of glycosylation patterns of various biologically important proteins represent a key field for the understanding of their complex structure-function relationships. However, the analysis of glycoprotein glycans is usually undermined by tedious sample processing steps prior to detection, including deproteination, desalting and removal of some other non-glycan impurities, which results in considerable sample loss and increased difficulty of quantitative analysis. Herein we report a facile and versatile method for the quantitative isolation of reducing glycans from complex samples using sulfonyl hydrazine-functionalized polystyrene (SHPS) beads, namely the SHPS-based glycan capturing procedure. This method allows the chemoselective and efficient condensation of the aldehyde group of reducing glycans with the active sulfonyl hydrazine group of SHPS beads under anhydrous conditions, resulting in the formation of sulfonyl hydrazone conjugates. The non-glycan components in samples, such as proteins, salts and some other impurities, can be completely removed by washing the sulfonyl hydrazone conjugates. Regeneration of the reducing glycans can be performed via mild hydrolysis of the washed sulfonyl hydrazone conjugates. This procedure is compatible with almost all the current techniques for the derivatization or detection of reducing glycans. We have obtained essential data for this method, including optimized reaction conditions, linearity and reproducibility for glycan quantitation, as well as a final glycan recovery ratio. Moreover, mass spectrometric analysis of the glycans from some complex biological samples, including milk, human blood plasma and fetal bovine serum, was achieved, demonstrating good applicability of this novel procedure.

Solid-phase glycan isolation for glycomics analysis

Glycosylation is one of the most significant protein PTMs. The biological activities of proteins are dramatically changed by the glycans associated with them. Thus, structural analysis of the glycans of glycoproteins in complex biological or clinical samples is critical in correlation with the functions of glycans with diseases. Profiling of glycans by HPLC-MS is a commonly used technique in analyzing glycan structures and quantifying their relative abundance in different biological systems. Methods relied on MS require isolation of glycans from negligible salts and other contaminant ions since salts and ions may interfere with the glycans, resulting in poor glycan ionization. To accomplish those objectives, glycan isolation and clean-up methods including SPE, liquid-phase extraction, chromatography, and electrophoresis have been developed. Traditionally, glycans are isolated from proteins or peptides using a combination of hydrophobic and hydrophilic columns: proteins and peptides remain on hydrophobic absorbent while glycans, salts, and other hydrophilic reagents are collected as flowthrough. The glycans in the flowthrough are then purified through graphite-activated carbon column by hydrophilic interaction LC. Yet, the drawback in these affinity-based approaches is nonspecific binding. As a result, chemical methods by hydrazide or oxime have been developed for solid-phase isolation of glycans with high specificity and yield. Combined with high-resolution MS, specific glycan isolation techniques provide tremendous potentials as useful tools for glycomics analysis.