Capillary electrochromatographic separation of peptides using a macrocyclic polyamine for molecular recognition

Fabrication and evaluation of tetraazahexaphenylmacrocycle-bonded stationary phase with multiple retention mechanisms

A 34-membered tetraazahexaphenylmacrocycle (N₄Ph₆) with a rigid π-conjugated moiety was chemically bonded to silica gel with 3-chloropropyltrimethoxysilane as the coupling agent to prepare a novel SiO₂@N₄Ph₆ stationary phase. Several common organic analytes, including alkylbenzenes, polycyclic aromatic hydrocarbons, anilines, phenols, phthalates, and folic acid, were selected as probes to investigate its chromatographic performance. The as-developed SiO₂@N₄Ph₆ stationary phase showed superiority retention and high selectivity for probe molecules through multiple interactions, including hydrophobic, π-π, hydrogen-bonding, and steric interactions. Density functional theory calculation results using folic acid as model solute provided an intuitive and a quantitative description of the multiple retention mechanisms.

Stationary phases for the enrichment of glycoproteins and glycopeptides

The analysis of protein glycosylation is important for biomedical and biopharmaceutical research. Recent advances in LC-MS analysis have enabled the identification of glycosylation sites, the characterisation of glycan structures and the identification and quantification of glycoproteins and glycopeptides. However, this type of analysis remains challenging due to the low abundance of glycopeptides in complex protein digests, the microheterogeneity at glycosylation sites, ion suppression effects and the competition for ionisation by co-eluting peptides. Specific sample preparation is necessary for comprehensive and site-specific glycosylation analyses using MS. Therefore, researchers continue to pursue new columns to broaden their applications. The current manuscript covers recent literature published from 2008 to 2013. The stationary phases containing various chemical bonding methods or ligands immobilisation strategies on solid supports that selectively enrich N-linked or sialylated N-glycopeptides are categorised with either physical or chemical modes of binding. These categories include lectin affinity, hydrophilic interactions, boronate affinity, titanium dioxide affinity, hydrazide chemistry and other separation techniques. This review should aid in better understanding the syntheses and physicochemical properties of each type of stationary phases for enriching glycoproteins and glycopeptides.