Preparation of epoxy-functionalized hierarchically porous hybrid monoliths via free radical polymerization and application in HILIC enrichment of glycopeptides

Covalent organic frameworks based hierarchical porous hybrid monolithic capillary: Synthesis, characterization, and applications in trace metals analysis

The preparation of hierarchical porous monolithic column with high covalent organic frameworks (COF) loading and micropores accessibility is challenging due to the easy aggregability and sedimentation of COFs. Herein, a novel strategy based on high internal phase emulsion (HIPE) polymerization was proposed for preparing COF hybrid capillary monolithic column with hierarchical porosity. COFs with different frameworks including imine COFs (COF-OMe, COF-F and COF-SH), triazine COF (CTF-1) and boron-based COF (COF-5) were selected to investigate the universality of the preparation strategy. The presence of COF in the monolithic capillary was confirmed by scanning electron microscope, X-ray diffraction and fourier transform infrared spectroscopy. Nitrogen adsorption/desorption experiments and thermogravimetric analysis showed that the prepared COF hybrid monolithic capillary exhibited high COF loading (e.g., 28.7% for COF-SH) and accessibility (e.g., 98.5% for COF-SH), mainly due to the thin walls of void-window structures originated from polymerization of HIPE. The successful preparation of water-stable COF-F, COF-OMe, COF-SH and CTF-1 hybrid monolithic columns demonstrated the proposed synthesis strategy is universal to water-stable COF without tedious optimization of dispersion system, effectively avoiding the sedimentation of COF in pre-polymerization solution. Then, the sulfhydryl-modified COF hybrid polymer (poly(COF-SH-HIPE)) monolithic column was evaluated for the extraction of heavy metal ions, and a method based on poly(COF-SH-HIPE) monolithic capillary microextraction on-line coupled with inductively coupled plasma mass spectrometry detection was developed for analysis of trace Cd, Hg and Pb in human fluid samples.

Review of recent advances in development and applications of organic-silica hybrid monoliths

Organic-silica hybrid monoliths attracted attention as an alternative to extensively researched organic polymer-based and silica-based counterparts. The development and applications of these materials as extraction and separation media in capillary liquid chromatography and capillary electrochromatography were previously reviewed in several manuscripts. In this review, we will concentrate on work published since mid-2016 focusing on advances in their development using sol-gel chemistry of tetra- and trialkoxysilanes and subsequent surface modification with organic monomers, and "one-pot" strategy incorporating sol-gel chemistry of alkoxysilanes and free-radical polymerization, ring-opening polymerization, or thiol-based click polymerization with organic monomers. Approaches adapted to the preparation of hybrid monoliths made with polyhedral oligomeric silsesquioxanes will be covered as well.

Effect of Silane Monolayers and Nanoporous Silicon Surfaces on the Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Detection of Sepsis Metabolites Biomarkers Mixed in Solution

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS) is a promising strategy for clinical diagnosis based on metabolite detection. However, several bottlenecks (such as the lack of reproducibility in analysis, the presence of an important background in low-mass range, and the lack of organic matrix for some molecules) prevent its transfer to clinical cases. These limitations can be addressed by using nanoporous silicon surfaces chemically functionalized with silane monolayers. In the present study, sepsis metabolite biomarkers were used to investigate the effects of silane monolayers and porous silicon substrates on MALDI-ToF MS analysis (signal-to-noise value (S/N), relative standard deviation of the S/N of triplicate samples (STDmean), and intra-substrates uniformity). Also, the impact of the physicochemical properties of metabolites, with different isoelectric points and hydrophobic-hydrophilic balances, was assessed. Four different silane molecules, with various alkyl chain lengths and head-group charges, were self-assembled in monolayers on plane and porous silicon surfaces. Their surface coverage and conformity were investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The seven metabolites detected on the stainless-steel target plate (lysophosphatidylcholine, caffeine, phenylalanine, creatinine, valine, arginine, and glycerophosphocholine) are also detected on the silanized and bare, plane and porous silicon surfaces. Moreover, two metabolites, glycine and alanine, which are not detected on the stainless-steel target plate, are detected on all silanized surfaces, except glycine which is not detected on CH3 short-modified porous silicon and on the bare plane silicon substrate. In addition, whatever the metabolites (except phenylalanine and valine), at least one of the silicon surfaces allows to increase the S/N value in comparison with the stainless-steel target plate. Also, the heterogeneity of matrix crystallization features is linked to the STDmean which is poor on the NH3+ monolayer on plane substrate and better on the NH3+ monolayer on porous substrate, for most of the metabolites. Nevertheless, matrix crystallization features are not sufficient to systematically get high STDmean and uniformity in MALDI-ToF MS analysis. Indeed, the physicochemical properties of metabolites and surfaces, limitations in metabolite extraction from the pores, and improvement in metabolite desorption due to the pores are shown to significantly impact MS analysis. In particular, in the case of the most hydrophobic metabolites studied, the highest S/N values and the best STDmean and uniformity (the lowest values) are reached by using porous substrates, while in the case of the most hydrophilic metabolites studied, plane substrates demonstrated the highest S/N and the lowest STDmean. No clear trend of surface chemistry was evidenced.

Macrocyclic Antibiotics as Effective Chiral Selectors in Liquid Chromatography for Enantiomeric Separation of Pharmaceutical Compounds: A Review

Chiral separation techniques play a crucial role in the pharmaceutical industry, where the enantiomeric purity of drugs can have a significant impact on their efficacy and safety. Macrocyclic antibiotics are highly effective chiral selectors used in various chiral separation techniques, including LC, HPLC, SMB, and TLC, offering reproducible results and a wide range of applications. However, developing robust and efficient immobilization mechanisms for these chiral selectors remains a challenge. This review article focuses on various immobilization approaches, such as immobilization, coating, encapsulation, and photosynthesis, that have been applied to immobilize macrocyclic antibiotics on their support. Commercially available macrocyclic antibiotics for conventional liquid chromatography include Vancomycin, Norvancomycin, Eremomycin, Teicoplanin, Ristocetin A, Rifamycin, Avoparcin, Bacitracin, and others. In addition, capillary (nano) liquid chromatography has also been used in chiral separation utilizing Vancomycin, Polymyxin B, Daptomycin, and Colistin Sulfate. Macrocyclic antibiotic-based CSPs have been extensively applied due to their reproducible results, ease of use, and broad range of applications, capable of separating a large number of racemates.

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.

Facile Fabrication of Hierarchically Porous Boronic Acid Group-Functionalized Monoliths With Optical Activity for Recognizing Glucose With Different Conformation

At present, various materials based on helical polymers are nanoparticle or microsphere, which is not ease of use in practical application. Accordingly, facile preparation hierarchically porous monolith based on helical polymer needs to be developed. Herein, hierarchically porous boronic acid group-functionalized monoliths that exhibited optical activity were fabricated with a facile method based on crosslinking and polymerization-induced phase separation (CPIPS). Chiral substituted acetylene and achiral substituted acetylene with a boronic acid group were used as monomers. By regulating the composition of the pre-polymerization solution, the permeability and macropore size of the porous structure could be controlled. The hierarchically porous structure and large surface area were confirmed by scanning electron microscopy and nitrogen gas adsorption/desorption isotherms. In particular, the boronic acid functional group that can interact with a cis-diol group was successfully introduced on the skeleton surface of the monoliths. Further, the main chain of the copolymer that constituted the monoliths exhibited a high cis content and tacticity, and the monoliths showed good optical activity. Thus, the present study established a facile method to synthesize hierarchically porous boronic acid group-functionalized monoliths with optical activity via CPIPS, and the monoliths showed potential in recognition, separation, and adsorption of compound with chirality and cis-diol groups.

A review on recent advances in the enrichment of glycopeptides and glycoproteins by liquid chromatographic methods: 2016-Present

Among various protein post-translational modifications (PTMs), glycosylation has received special attention due to its immense role in molecular interactions, cellular signal transduction, immune response, etc. Aberration in glycan moieties of a glycoprotein is associated with cancer, diabetes, and bacterial and viral infections. In biofluids (plasma, saliva, urine, milk, etc.), glycoproteins are low in abundance and are masked by the presence of high abundant proteins. Hence, prior to their identification using mass spectrometry methods, liquid chromatography (LC)-based approaches were widely used. A general enrichment strategy involves a protein digestion step, followed by LC-based enrichment and desorption of glycopeptides, and enzymatic excision of the glycans. The focus of this review article is to highlight the articles published since 2016 that dealt with different LC-based approaches for glycopeptide and glycoprotein enrichment. The preparation of stationary phases, their surface activation, and ligand immobilization strategies have been discussed in detail. Finally, the major developments and future trends in the field have been summarized.

Fabrication of hydrophilic zwitterionic microspheres via inverse suspension polymerization for the enrichment of N-glycopeptides

A kind of zwitterionic microsphere was prepared via one-step inverse suspension polymerization employing 3-[N,N-dimethyl-[2-(2-methylpropyl-2-enyloxy) ethyl] ammonium] propane-1-sulfonate (MSA) and N,N-methylene bisacrylamide (BIS) as the precursors. The preparation conditions were carefully investigated and optimized by regulating the content of total monomers, ratio of MSA to BIS, ratio of water to oil, and content of stabilizer. The properties of microspheres were characterized by helium ion microscopy (HIM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption measurement, and water contact angle measurement. The particle size of resulting polydisperse microspheres ranged from 15-25 μm, exhibiting high specific surface area of 138 m² g^-1. Owing to great hydrophilicity, the resulting zwitterionic microspheres could be directly used as hydrophilic interaction chromatography (HILIC) sorbent to enrich glycopeptides from biosamples without any chemical modification. A total of 19 N-glycopeptides was enriched from 10 μg of IgG digest. Besides, up to 383 N-glycopeptides and 224 N-glycosylation sites were unambiguously identified from 2 μL of human serum digest by cLC-MS/MS after enrichment with zwitterionic microspheres, indicating their great enrichment performance to N-glycopeptides. The approach of preparing hydrophilic zwitterionic microspheres contains only one synthesis reaction and is suitable for large-scale preparation.

One-step synthesis of hydrophilic microspheres for highly selective enrichment of N-linked glycopeptides

A polyacrylamide-based hydrophilic microsphere with a lot of hydroxyl groups on surface (PAM-OH HMS) was prepared in one step. The synthetic process was simple reverse suspension polymerization without any chemical derivation or grafting steps. The properties of obtained HMS were characterized by scanning electron microscopy (SEM), static water contact angle measurement, and FT-IR. The abundant hydroxyl groups on the surface make the material highly good hydrophilic and thus it was utilized for N-glycopeptides enrichment. The enrichment efficiency of PAM-OH HMSs was demonstrated by capturing N-linked glycopeptides from tryptic digest of human immunoglobulin G (IgG). The detection sensitivity for N-glycopeptides identification by MALDI-TOF MS was as low as 10 fmol for tryptic digest of standard human IgG. The selectivity of the HMS towards N-glycopeptides had almost no decrease when the molar ratio of BSA tryptic digest to IgG tryptic digest was increased from 10:1 to 100:1. Moreover, in the LC-MS/MS analysis of real biological sample, a total of 344 unique N-glycosites in 598 unique N-glycopeptides from 172 N-glycoproteins were identified from 2 μL human serum after deglycosylated by PNGase F, and 825 intact N-glycopeptides with different types of glycoform were detected when directly analyzed the N-glycopeptides enriched by PAM-OH HMS. To show the potential of our material in solving real biological issues, N-glycopeptides in the serum from hepatocelluar carcinoma (HCC) patient and health control were enriched and quantified. All the experiments demonstrated that this polyacrylamide-based hydrophilic microsphere shows a great potential to enrich the low-abundance N-glycopeptides for glycoproteome analysis of real complicated biological samples.

Signature-Ion-Triggered Mass Spectrometry Approach Enabled Discovery of N- and O-Linked Glycosylated Neuropeptides in the Crustacean Nervous System

Crustaceans are commonly used model organisms to study neuromodulation. Despite numerous reported crustacean neuropeptide families and their functions, there has been no report on neuropeptide glycosylation. This is in part due to a lack of sensitive methods that enable deciphering this intricate low-abundance post-translational modification, even though glycosylation has been shown to play an important role in neuromodulation. Here, we describe the discovery of glycosylated neuropeptides with an enrichment-free approach, taking advantage of signature oxonium ions produced in higher-energy collision dissociation (HCD) MS/MS spectra. The detection of the oxonium ions in the HCD scans suggests glycan attachment to peptides, allowing electron-transfer/higher-energy collision dissociation (EThcD) to be performed to selectively elucidate structural information of glycosylated neuropeptides that are buried in nonglycosylated peptides. Overall, 4 N-linked and 14 O-linked glycosylated neuropeptides have been identified for the first time in the crustacean nervous system. In addition, 91 novel putative neuropeptides have been discovered based on the collected HCD scans. This hybrid approach, coupling a shotgun method for neuropeptide discovery and targeted strategy for glycosylation characterization, enables the first report on glycosylated neuropeptides in crustaceans and the discovery of additional neuropeptides simultaneously. The elucidation of novel glycosylated neuropeptides sheds light on the crustacean peptidome and offers novel insights into future neuropeptide functional studies.

Silica-Based Sol-Gel Coating with High Transmission at 1053 and 527 nm and Absorption at 351 nm for Frequency-Converting Crystals in High-Power Laser System

A high-power laser system is employed to drive the fusion ignition to realize sustainable supply of green energy according to the inertial confinement fusion theory, in which frequency-converting crystals are sealed in the terminal vacuum chamber and utilized to turn the incident laser (1053 nm) to the desired one (351 nm). However, the reflected 351 nm laser from the pellet hohlraum that goes back through the frequency-converting crystal is found to be harmful for the upstream elements that are located before the terminal chamber. In this study, a specialized coating system for the frequency-converting crystals was designed and fabricated to both ensure high output power for the fusion and reduce the reflected 351 nm laser energy by absorption. Furthermore, the structural, mechanical, and laser-damage resistant properties of this coating were investigated as well.

Advances in hydrophilic nanomaterials for glycoproteomics

Owing to the formidable challenge posed by microheterogeneities in glycosylation sites, macroheterogeneity of the modification number of glycans, and low abundance and ionization efficiency of glycosylation, the crucial premise for conducting in-depth profiling of the glycoproteome is to develop highly efficient technology for separation and enrichment. The appearance of hydrophilic interaction chromatography (HILIC) has considerably accelerated the progress in glycoproteomics. In particular, additional hydrophilic nanomaterials have been developed for glycoproteomics research in the recent years. In this review, we mainly summarize the recent progresses made in the design and synthesis of different hydrophilic nanomaterials, as well as their applications in glycoproteomics, according to the classification of the main hydrophilic functional molecules on the surface. Further, we briefly illustrate the potential retention mechanism of the HILIC mode and discuss the limits and barriers of hydrophilic nanomaterials in glycoproteomics, as well as propose their possible development trends in the future.