Preparation of iminodiacetic acid functionalized silica capillary trap column for on-column selective enrichment of N-linked glycopeptides

Preparation and application of UPLC silica microsphere stationary phase:A review

In this review, microspheres for ultra-performance liquid chromatography (UPLC) were reviewed in accordance with the literature in recent years. As people's demands for chromatography are becoming more and more sophisticated, the preparation and application of UPLC stationary phases have become the focus of researchers in this field. This new analytical separation science not only maintains the practicality and principle of high-performance liquid chromatography (HPLC), but also improves the step function of chromatographic performance. The review presents the morphology of four types of sub-2 μm silica microspheres that have been used in UPLC, including non-porous silica microspheres (NPSMs), mesoporous silica microspheres (MPSMs), hollow silica microspheres (HSMs) and core-shell silica microspheres (CSSMs). The preparation, pore control and modification methods of different microspheres are introduced in the review, and then the applications of UPLC in drug analysis and separation, environmental monitoring, and separation of macromolecular proteins was presented. Finally, a brief overview of the existing challenges in the preparation of sub-2 μm microspheres, which required further research and development, was given.

Application of Microscopic Highly Hydrophilic Silica-Based Nanocomposites with High Surface Exposure in the Efficient Identification of Intact N-Glycopeptides

Glycosylation of proteins regulates the life activities of organisms, while abnormalities of glycosylation sites and glycan structures occur in various serious diseases such as cancer. A separation and enrichment procedure is necessary to realize the analysis of the glycoproteins/peptides by mass spectrometry, for which the surface hydrophilicity of the material is an important factor for the separation and enrichment performance. In the present work, under the premise of an obvious increase of the surface silicon exposure (79.6%), the amount of surface polar silanol is remarkably generated accompanying the introduction of the active amino groups on the surface of silica. The microscopic hydrophilicity, which is determined with water physical-adsorption measurements and can directly reflect the interaction of water molecules and the intrinsic surface of the material, maximally increases by 44%. This microscopically highly hydrophilic material shows excellent enrichment ability for glycopeptides, such as extremely low detection limits (0.01 fmol μL^-1), remarkable selectivity (1:8000), and size exclusion effects (1:8000). A total of 677 quantifiable intact N-glycopeptides were identified from the serum of patients with cervical cancer, and the glycosylation site and glycan structure were analyzed in depth, indicating that this novel material can show a broad practical application in cervical cancer diagnosis.

Non-ceruloplasmin-bound copper and copper speciation in serum with extraction using functionalized dendritic silica spheres followed by ICP-MS detection

The quantification of non-ceruloplasmin-bound copper (NCBC) and total copper in biological fluids is highly required for understanding the correlation of copper with various physiological processes and diseases. In the present work, we developed dendritic spherical silica particles functionalized with EDTA, shortly as DMSPs-EDTA, from the hydrolysis of tetraethyl orthosilicate with the aid of structure-directing agents and subsequent modification of EDTA. DMSPs-EDTA serves as adsorbent with abundant binding sites to facilitate efficient extraction of NCBC. The retained NCBC on DMSPs-EDTA may be readily recovered by stripping with HNO₃ (2 mol L^-1). By hyphenating with ICP-MS detection, it provides a limit of detection of 1.3 pmol for NCBC. The degradation of ceruloplasmin with 200 mmol L^-1 H₂O₂ releases the bound copper as NCBC to distribute among other ligands, which may be efficiently retained by the adsorbent and facilitate the detection of total copper. The linear ranges of 0.21-10 μmol L^-1 and 0.42-30 μmol L^-1 were derived for the detection of NCBC and total copper. The recovery rates for spiked NCBC or total copper in serum were derived to be 97-108% and 94-102%, respectively. The analysis of serum for a healthy subject resulted in 1.8 μmol L^-1 NCBC and 9.5 μmol L^-1 total copper. In addition, the proportions of 8.5-12% for NCBC were derived from the serum of healthy adults, while those for the patients with lung, hepatocellular and esophageal carcinoma were found to be 10-12%, illustrating no obvious difference against the normal group.

A protocol of carbonized on-column enrichment for urinary exosomal N-glycans profiling

As a widely present vesicle, exosome plays an important role in lots of biological processes due to its inclusive cargos. In particular, exosome glycan cargo is attracting attentions since its aberrant alteration is closely related to many progressions in diseases. In this work, a novel carbonized packing capillary trap column for urinary exosomal N-glycan enrichment was proposed. The carbonized packing exhibited large specific surface area, mesoporous structure with narrow pore size distribution and abundant carbon for specially interacting with oligosaccharides. Benefitting from all these advantages, the N-glycans deriving from standard glycoproteins or complex human urine exosomes could be identified with high sensitivity and selectivity. Finally, from the glycans identified in healthy volunteers and patients with bladder carcinoma, we observed that 10 of glycans shared by two groups were obvious downregulation and the 18 were upregulation. These results show great potential of capillary trap column as a tool for the enrichment and detection of glycans in exosomal, attracting more attention on disease progression monitoring and biomarker discovery.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

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.

The mechanism of cadmium sorption by sulphur-modified wheat straw biochar and its application cadmium-contaminated soil

Cadmium (Cd) pollution in soils has received considerable research attention globally, and sulphur-modified biochar (SBC) could combine the advantages of biochar and the sulphur element for Cd remediation. Biochar from agricultural waste is feasible, which has a low preparation cost. However, there are few studies regarding the effects of the sulphur modification of biochar on the Cd immobilization mechanism. This study aimed to research the Cd immobilization mechanism of pristine wheat straw biochar (BC) and sulphur-modified biochar (SBC), and the Cd immobilization effects of BC and SBC in Cd-contaminated soils. Elemental and SEM analysis confirmed that sulphur was successfully loaded on the pristine biochar. XPS analysis confirmed that there was a considerable discrepancy between adsorption mechanisms of Cd on BC and SBC. In particular, cadmium sorption on BC was due to Cd(OH)₂ and CdCO₃ precipitation formation and interaction with carbonyl and carboxyl groups, whereas on SBC, sorption was mainly due to CdS and CdHS⁺ formation and interaction with organic sulphide. In the incubation experiment, SBC and BC additions increased pH value and also reduced the available Cd concentrations in the soil. Compared with the control, the contents of available Cd in soil were significantly decreased by 15.86% ~ 22.10% and 22.72% ~ 27.90%, following treatments with BC and SBC, respectively.

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.

A capillary column packed with a zirconium(IV)-based organic framework for enrichment of endogenous phosphopeptides

A zirconium(IV)-based metal organic framework (Zr-MOF) was deposited on polydopamine-coated silica microspheres to form microspheres of type SiO₂@PDA@Zr-MOF. These were packed into capillary columns for enrichment of phosphopeptides. The column was off-line coupled to both matrix-assisted laser desorption/ionization time of flight mass spectrometry and LC-ESI-MS/MS. The method has a detection limit as low as 4 fmol of β-casein digest and a selectivity as high as 1:1000 (molar ratio of β-casein and BSA digest). It was applied to the analysis of human saliva. In total, 240 endogenous phosphopeptides were identified in only 25 μL human saliva. Graphical abstract A zirconium-based metal organic framework (Zr-MOF) was modified outside of polydopamine-coated silica microspheres to form microspheres named SiO₂@PDA@Zr-MOF. Then they were packed in capillary columns for selective enrichment of phosphopeptides via interaction between Zr-O clusters and phosphate groups. The pre-concentration resulted in a better detection of phosphopeptides by mass spectrometry. Tris: Tris(hydroxymethyl)aminomethane; DMF: Dimethyl Formamide; Zr-MOF: Zirconium(IV)-organic framework; MOAC: Metal oxide affinity chromatography.