Synthesis and Characterization of Hydrazide-Linked and Amide-Linked Organic Polymers

Four kinds of either hydrazide-linked or amide-linked polymers were facilely synthesized by using hydrazine, tetrakis­(4-aminophenyl)­methane (TAPM), terephthaloyl chloride (TPC), and trimesoyl chloride (TMC) as building blocks. The morphology, porosity, composition, and surface property of polymers were characterized by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption measurement, ¹³C/CP-MAS NMR, X-ray photoelectron spectroscopy, etc. The results indicated that building blocks had important effects on morphology and porosity. Poly­(TMC–TAPM) synthesized with TMC and TAPM showed the highest surface area of 241.9 m² g^–1. In addition, note that a hollow structure with ∼20 nm wall thickness was formed in poly­(TMC–hydrazine) prepared with TMC and hydrazine. Further study indicated that both carboxyl groups (−COOH) and hydrazide groups (−CONH–NH₂) existed on the surface of poly­(TMC–hydrazine), besides the mainly hydrazide linkage (−CONH–NHOC−). Taking advantages of good hydrophilicity and special functional groups on the surface, we finally adopted poly­(TMC–hydrazine) to enrich glycopeptides from tryptic digest via both hydrophilic interaction chromatography method with identification of 369 unique N-glycosylation sites and hydrazide chemistry method with identification of 88 unique N-glycosylation sites, respectively

Thiol-Epoxy Click Polymerization for Preparation of Polymeric Monoliths with Well-Defined 3D Framework for Capillary Liquid Chromatography

A facile approach was developed for direct preparation of organic monoliths via the alkaline-catalyzed thiol-epoxy click polymerization. Two organic monoliths were prepared by using tetraphenylolethane glycidyl ether as a multiepoxy monomer, and trimethylolpropane tris­(3-mercaptopropionate) and pentaerythritol tetrakis­(3-mercaptopropionate) as the multithiol monomer, respectively, in the presence of a ternary porogenic system (DMSO/PEG200/H₂O). The obtained organic monoliths showed high thermal, mechanical and chemical stabilites. Benefiting from the step-growth polymerization process, two organic monoliths possessed well-defined 3D framework microstructure, and exhibited high permeabilities and column efficiencies in capillary liquid chromatography. A series of neutral, basic and acidic small molecules were used to comprehensively evaluate the separation abilities of these monoliths, and satisfactory chromatographic performance with column efficiencies ranged from 35 500 to 132 200 N/m was achieved, demonstrating good separation abilities of these organic monoliths prepared via thiol-epoxy click polymerization approach. Besides, multiple retention mechanisms, including hydrophobic, hydrophilic and π–π conjugate interactions were observed during the separation of analytes on these monoliths, which would make them promising for more extensive applications in capillary liquid chromatography

Preparation of Polypropylene Spin Tips Filled with Immobilized Titanium(IV) Ion Monolithic Adsorbent for Robust Phosphoproteome Analysis

In this study, we developed a Ti­(IV) monolithic spin tip for phosphoproteome analysis of a minute amount of biological sample for the first time. The surface of polypropylene pipet tip was activated by the photoinitiator benzophenone under UV light radiation followed by polymerization of ethylene glycol methacrylate phosphate and bis-acrylamide in the tip to form a porous monolith with reactive phosphate groups. The as-prepared tips grafted with monolithic adsorbent were then chelated with titanium­(IV) ion for phosphopeptide enrichment. It was found that the tips enabled fast and efficient capture of phosphopeptides from microscale complex samples. The monolithic tip was demonstrated to have a detection limit as low as 5 fmol β-casein tryptic digest, along with an exceptionally high specificity to capture phosphopeptides from complex tryptic digest mixed with an unphosphorylated protein and a phosphorylated protein at a molar ratio up to 1000:1. When the tip was applied to enrich phosphopeptides from 5 μg of tryptic digest of complex HeLa cell proteins, 1185 high confidence of phosphorylated sites were successfully identified with the specificity as high as 92.5%. So far, this is the most sensitive phosphoproteomics analysis using a standard liquid chromatography–tandem mass spectrometry (LC–MS/MS) system for proteome-wide phosphorylation analysis in mammalian cells

Facile Preparation of Titanium(IV)-Immobilized Hierarchically Porous Hybrid Monoliths

Hierarchically porous materials have become a key feature of biological materials and have been widely applied for adsorption or catalysis. Herein, we presented a new approach to directly prepare a phosphate-functionalized hierarchically porous hybrid monolith (HPHM), which simultaneously contained mesopores and macropores. The design was based on the copolymerization of polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and vinylphosphonic acid (VPA) by adding degradable polycaprolactone (PCL) additive. The phosphate groups could be directly introduced into the hybrid monoliths. This approach was simple and time-saving, and overcame the defect of a rigorous, complex process for preparing traditional Ti⁴⁺-immobilized metal ion affinity chromatography (IMAC) materials. The specific surface area of an optimal hybrid monolith could reach 502 m²/g obtained by nitrogen adsorption/desorption measurements, which originated from the degradation of PCL. Meanwhile, the characterization of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) also suggested that the macropores existed in the hybrid monoliths. The size of macropores could be controlled by the content of PCL in the polymerization mixture. The prepared Ti⁴⁺-IMAC HPHMs exhibited high adsorption capacity (63.6 mg/g for pyridocal 5′-phosphatemonohydrate), and excellent enrichment specificity (tryptic digest of β-casein/BSA at a molar ratio of 1:1000) and sensitivity (tryptic digest of 5 fmol of β-casein). Moreover, the Ti⁴⁺-IMAC HPHMs provided effective enrichment ability of low-abundance phosphopeptides from human serum and HeLa cell digests