High-efficiency two-dimensional separation of natural products based on β-cyclodextrin stationary phase working in both hydrophilic and reversed hydrophobic modes.

Natural products are rather complex samples containing a large number of compounds ranging from polar to nonpolar, small molecules to macromolecules, as well as numerous homologs/analogs with quite similar structures, which create great opportunities and treasures for discovery of bioactive drugs. For the purpose of better understanding the complex natural products and controlling their qualities, powerful analytical techniques for adequately separating chemical constituents and tracking potentially bioactive components are quite essential. Here, a design concept of bidirectional β-cyclodextrin (β-CD)-modified chromatographic stationary phase toward separation of bufadienolides extracted from toad is proposed.

[Covalent organic framework functional materials and their applications in glycopeptide enrichment].

Protein glycosylation is among the most important post-translational modifications in living organisms and the research in the field of protein glycosylation continues to garner attention. Currently, the efficient separation and enrichment of glycoproteins and glycopeptides is the primary challenge of glycoproteomics research. The number of glycoproteins is small in complex biological samples.

Hydrophilic graphene oxide-dopamine-cationic cellulose composites and their applications in N-Glycopeptides enrichment.

Glycosylation is one of the most important post-translational modifications of proteins, and plays an important role in the structure and function of proteins. However, due to the diversity of glycopeptide forms and their low abundance, it is extraordinarily challenging to capture and separate glycopeptides with high selectivity from complex biological samples with mass spectrometric analysis. Here, we synthesized a new type of hydrophilic composite based on electrostatic interactions, which has been proven to be effective in immobilizing cationic cellulose on graphene oxide-dopamine carriers (expressed as GO-DA-JR), for highly specific enrichment of N-glycopeptides.

Synthesis of Al-doping-TiO monodisperse microspheres and their application for phosphopeptides and glycopeptides enrichment.

Glycosylation and phosphorylation are two of the most common and important post-translational modifications (PTMs) of proteins, which play critical roles in regulating a variety of complex biological processes and involvement in many diseases. Due to the low abundance of phosphopeptides and glycopeptides, highly selective enrichment methods are crucial to the identification of protein phosphorylation and glycosylation by mass spectrometry (MS). Here, monodisperse uniform Al-doping-TiO mixed oxide microspheres were easily synthesized.

Highly Efficient Separation of Methylated Peptides Utilizing Selective Complexation between Lysine and 18-Crown-6.

Protein methylation is one of the most common and important post-translational modifications, and it plays vital roles in epigenetic regulation, signal transduction, and chromatin metabolism. However, due to the diversity of methylation forms, slight difference between methylated sites and nonmodified ones, and ultralow abundance, it is extraordinarily challenging to capture and separate methylated peptides from biological samples. Here, we introduce a simple and highly efficient method to separate methylated and nonmethylated peptides using 18-crown-6 as a mobile phase additive in high-performance liquid chromatography.

Hydrophilic Nanocomposite Functionalized by Carrageenan for the Specific Enrichment of Glycopeptides.

A hydrophilic nanocomposite was synthesized by an easy route to improve glycopeptides enrichment efficiency. This new composite, prepared with a method based on electrostatic interaction, was demonstrated to be efficient for immobilization of carrageenan on graphene oxide/poly(ethylenimine) support (denoted as GO-PEI-Carr). Carrageenan, which has a large number of hydroxyl groups and is fully negatively charged, is a new modified phase of hydrophilic materials in glycoproteomics.

Hydrophilic Phytic Acid-Coated Magnetic Graphene for Titanium(IV) Immobilization as a Novel Hydrophilic Interaction Liquid Chromatography-Immobilized Metal Affinity Chromatography Platform for Glyco- and Phosphopeptide Enrichment with Controllable Selectivity.

In this work, multifunctional Ti-immobilized phytic acid-modified magnetic graphene (denoted as MagG@PEI@PA-Ti) nanocomposites were fabricated through a facile route for simultaneous/respective enrichment of N-glyco- and phosphopeptides. Phytic acid (PA), with six phosphate groups, possesses excellent hydrophilicity and metal ion coordination ability, which endowed the MagG@PEI@PA-Ti with combined properties of immobilized metal ion affinity chromatography (IMAC)- and hydrophilic interaction liquid chromatography (HILIC)-based materials. On the basis of the different binding ability of N-glyco- and phosphopeptides on MagG@PEI@PA-Ti, the MagG@PEI@PA-Ti nanocomposites could enrich N-glyco- and phosphopeptides simultaneously or respectively by using different enrichment conditions, achieving controllable selective enrichment of N-glyco- and phosphopeptides.

Highly efficient enrichment of phosphopeptides from HeLa cells using hollow magnetic macro/mesoporous TiO nanoparticles.

In this work, hollow magnetic macro/mesoporous TiO nanoparticles (denoted as FeO@H-fTiO) were synthesized by a facile "hydrothermal etching assisted crystallization" route to improve the phosphopeptide enrichment efficiency. The porous nanostructure of TiO shell and large hollow space endowed the FeO@H-fTiO with a high surface area (144.71 m g) and a large pore volume (0.

Dendritic Mesoporous Silica Nanoparticles with Abundant Ti for Phosphopeptide Enrichment from Cancer Cells with 96% Specificity.

Selective enrichment and sensitive detection of phosphopeptides are of great significance in many bioapplications. In this work, dendritic mesoporous silica nanoparticles modified with polydopamine and chelated Ti (denoted DMSNs@PDA-Ti) were developed to improve the enrichment selectivity of phosphopeptides. The unique central-radial pore structures endowed DMSNs@PDA-Ti with a high surface area (362 m g), a large pore volume (1.

Selective enrichment of N-linked glycopeptides and glycans by using a dextran-modified hydrophilic material.

Glycosylation analysis of proteins from biological sources utilizing mass spectrometry based approaches is challenging due to the relatively low abundance of glycopeptides, the structural diversity of glycans, and the coexisting matrices. In this study, a customized dextran-bonded silica-based stationary phase was introduced for selective enrichment of glycopeptides and glycans from complex biological samples. This material has exhibited superior selectivity and broader glycosylation site coverage over commercial Sepharose in glycoproteomic evaluation.

Yolk-shell magnetic mesoporous TiO microspheres with flowerlike NiO nanosheets for highly selective enrichment of phosphopeptides.

In this work, we fabricated a yolk-shell magnetic composite that contains mesoporous TiO as the inner shell and flowerlike NiO as the outer shell (denoted as FeO@H-TiO@f-NiO) to reduce the limitations of single-component metal oxides in phosphopeptide enrichment. The NiO nanosheets play a synergistic role in phosphopeptide enrichment. And the unique flowerlike structure of NiO with sufficient space can facilitate the reversible insertion/extraction of peptides, which will have less impact on the enrichment process of the inner TiO shell.

Synthesis and evaluation of a maltose-bonded silica gel stationary phase for hydrophilic interaction chromatography and its application in Ginkgo Biloba extract separation in two-dimensional systems.

Maltose covalently bonded to silica was prepared by using carbonyl diimidazole as a cross-linker and employed as a stationary phase for hydrophilic interaction liquid chromatography. The column efficiency and the effect of water content, buffer concentration, and pH value influenced on retention were investigated. The separation or enrichment selectivity was also studied with nucleosides, saccharides, amino acids, peptides, and glycopeptides.

Sequential enrichment of singly- and multiply-phosphorylated peptides with zwitterionic hydrophilic interaction chromatography material.

An interesting and novel method for the selective and sequential enrichment of singly- and multiply-phosphorylated peptides with a zwitterionic material "Click TE-Cys" is presented. Retention mechanisms between phosphopeptides and Click TE-Cys are systematically investigated by checking the influence of acetonitrile content, pH value, and buffer concentration on the retention of phosphopeptides. Both hydrophilic interaction and electrostatic interaction are involved in retention between phosphopeptides and Click TE-Cys.

Evaluation of a silicon oxynitride hydrophilic interaction liquid chromatography column in saccharide and glycoside separations.

The retention characteristics of a silicon oxynitride stationary phase for carbohydrate separation were studied in hydrophilic interaction chromatography mode. Four saccharides including mono-, di-, and trisaccharides were employed to investigate the effects of water content and buffer concentration in the mobile phase on hydrophilic interaction liquid chromatography retention. For the tested saccharides, the silicon oxynitride column demonstrated excellent performance in terms of separation efficiency, hydrophilicity, and interesting separation selectivity for carbohydrates compared to the bare silica stationary phase.

A dextran-bonded stationary phase for saccharide separation.

A-saccharide-based stationary phase for hydrophilic interaction liquid chromatography (HILIC) is presented. The method uses carbonyl di-imidazole (CDI) as a cross-linker for dextran in aqueous solution. Different from the traditional immobilized saccharide stationary phase, this method was using a simple way to bond the high molecular of polysaccharide immobilized on the silica gel.

A novel ionic-bonded cellulose stationary phase for saccharide separation.

A hydrophilic interaction liquid chromatography (HILIC) stationary phase of cellulose-coated silica was synthesized as a novel saccharide separation material. The material, prepared with a method based on ionic interaction, was demonstrated to be efficient for immobilization of saccharides on silica supports. The method is more efficient than traditional immobilized saccharide stationary phase synthesis methods.

Sequential elution of multiply and singly phosphorylated peptides with polar-copolymerized mixed-mode RP18/SCX material.

Novel polar-copolymerized mixed-mode RP18/SCX material was developed for feasible phosphopeptide enrichment, in which multiply and singly phosphorylated peptides could be sequentially eluted and separated with high selectivity.

Selective enrichment of glycopeptides for mass spectrometry analysis using C18 fractionation and titanium dioxide chromatography.

Comprehensive glycoprotein characterization based on mass spectrometry (MS) is challenging because of low concentration of glycopeptides and suppression effect of abundant non-glycosylated peptides in MS. Therefore, it is vital to enrich glycopeptides before MS analysis. A new method was developed to selectively enrich glycopeptides from complex sample by coupling C18 fractionation with titanium dioxide (TiO(2)) enrichment.

Zirconia layer coated mesoporous silica microspheres as HILIC SPE materials for selective glycopeptide enrichment.

Characterization of protein glycosylation requires highly specific methods for the enrichment of glycopeptides because of their sub-stoichiometric glycosylation-site occupancy. The hydrophilic affinity based strategy has attracted more attention, owing to its broad glycan specificity, good reproducibility, and compatibility with mass spectrometric (MS) analysis. Several polar matrices have emerged for hydrophilic interaction chromatography (HILIC) approaches, including sepharose, cellulose, ZIC-HILIC and titania.