A metal oxide affinity probe derived from MIL-125 for selective enrichment of endogenous phosphopeptides

Highly effective enrichment of endogenous phosphopeptides from complex biological samples is an essential and crucial theme in the analysis of phosphopeptidomics. Herein, an ordered mesoporous TiO₂/C composite (denoted as Ti-MCM) was prepared by the pyrolysis of MIL-125 under a N₂ atmosphere. The obtained Ti-MCM possesses a high specific surface area (165 m² g^-1), a uniform pore size (3.75 nm), and a large amount of Ti (46%). By utilizing the selective chelation between Ti-MCM and phosphopeptides, 25 phosphopeptides were detected in α-casein digest after enrichment. The material shows good selectivity even in the presence of 2000-fold excess of interference peptides. It was also used to enrich endogenous phosphopeptides from the complex samples of human serum and saliva and showed a good performance.

Phosphopeptide Enrichment Using Various Magnetic Nanocomposites: An Overview

Magnetic nanocomposites are hybrid structures consisting of an iron oxide (Fe3O4/γ-Fe2O3) superparamagnetic core and a coating shell which presents affinity for a specific target molecule. Within the scope of phosphopeptide enrichment, the magnetic core is usually first functionalized with an intermediate layer of silica or carbon to improve dispersibility and increase specific area, and then with an outer layer of a phosphate-affinity material. Fe3O4-coating materials include metal oxides, rare earth metal-based compounds, immobilized-metal ions, polymers, and many others. This chapter provides a generic overview of the different materials that can be found in literature and their advantages and drawbacks.

A Ti4+-immobilized phosphate polymer-patterned silicon substrate for on-plate selective enrichment and self-desalting of phosphopeptides

A circular hydrophobic–hydrophilic-Ti⁴⁺ immobilized phosphate polymer is patterned as the sample support for selective enrichment, wash-free self-desalting and mass spectroscopy (MS) analysis of phosphopeptides.

Chemical sensing of neurotransmitters

This review focuses on the chemosensors for neurotransmitters published for the last 12 years, covering biogenic amines (dopamine, epinephrine, norepinephrine, serotonin, histamine and acetylcholine), amino acids (glutamate, aspartate, GABA, glycine and tyrosine), and adenosine.

Boronic acid-modified magnetic materials for antibody purification

Aminophenyl boronic acids can form reversible covalent ester interactions with cis-diol-containing molecules, serving as a selective tool for binding glycoproteins as antibody molecules that possess oligosaccharides in both the Fv and Fc regions. In this study, amino phenyl boronic acid (APBA) magnetic particles (MPs) were applied for the magnetic separation of antibody molecules. Iron oxide MPs were firstly coated with dextran to avoid non-specific binding and then with 3-glycidyloxypropyl trimethoxysilane to allow further covalent coupling of APBA (APBA_MP). When contacted with pure protein solutions of human IgG (hIgG) and bovine serum albumin (BSA), APBA_MP bound 170 ± 10 mg hIgG g(-1) MP and eluted 160 ± 5 mg hIgG g(-1) MP, while binding only 15 ± 5 mg BSA g(-1) MP. The affinity constant for the interaction between hIgG and APBA_MP was estimated as 4.9 × 10(5) M(-1) (Ka) with a theoretical maximum capacity of 492 mg hIgG adsorbed g(-1) MP (Qmax), whereas control particles bound a negligible amount of hIgG and presented an estimated theoretical maximum capacity of 3.1 mg hIgG adsorbed g(-1) MP (Qmax). APBA_MPs were also tested for antibody purification directly from CHO cell supernatants. The particles were able to bind 98% of IgG loaded and to recover 95% of pure IgG (purity greater than 98%) at extremely mild conditions.

Synthesis of Fe3O4/graphene/TiO2 composites for the highly selective enrichment of phosphopeptides from biological samples

In this work, Fe3O4/graphene/TiO2 composites with a large surface area were designed and synthesized for the selective extraction and enrichment of phosphopeptides from biological samples. First, magnetic graphene was prepared according to our previous method. Next, we made the Fe3O4/graphene/TiO2 composite precursor using tetrabutyl titanate. Fe3O4/graphene/TiO2 composites were obtained after solvothermal and calcination treatments. We used standard protein-digestion solutions and human liver samples to test the enrichment ability of the obtained Fe3O4/graphene/TiO2 composites. The experimental results demonstrate that Fe3O4/graphene/TiO2 composites have a good phosphopeptide enrichment ability.

Facile synthesis of alumina hollow spheres for on-plate-selective enrichment of phosphopeptides

Alumina hollow spheres were synthesized, spotted and sintered on a stainless-steel plate. These spots were used to selectively capture phosphopeptides from peptide mixtures and the captured target peptides could be analyzed by MALDI-MS. This provides a fast and efficient on-plate selective enrichment method for phosphopeptides investigation.