High-throughput analysis of therapeutic and diagnostic monoclonal antibodies by multicapillary SDS gel electrophoresis in conjunction with covalent fluorescent labeling.

Capillary gel electrophoresis (CGE) in the presence of sodium dodecyl sulfate (SDS) is a well-established and widely used protein analysis technique in the biotechnology industry, and increasingly becoming the method of choice that meets the requirements of the standards of International Conference of Harmonization (ICH). Automated single channel capillary electrophoresis systems are usually equipped with UV absorbance and/or laser-induced fluorescent (LIF) detection options offering general applicability and high detection sensitivity, respectively; however, with limited throughput. This shortcoming is addressed by the use of multicapillary gel electrophoresis (mCGE) systems with LED-induced fluorescent detection (LED-IF), also featuring automation and excellent detection sensitivity, thus widely applicable to rapid and large-scale analysis of biotherapeutics, especially monoclonal antibodies (mAb). The methodology we report in this paper is readily applicable for rapid purity assessment and subunit characterization of IgG molecules including detection of non-glycosylated heavy chains (NGHC) and separation of possible subunit variations such as truncated light chains (Pre-LC) or alternative splice variants. Covalent fluorophore derivatization and the mCGE analysis of the labeled IgG samples with multi-capillary gel electrophoresis are thoroughly described. Reducing and non-reducing conditions were both applied with and without peptide N-glycosidase F mediated deglycosylation.

Highly specific capture and direct MALDI MS analysis of phosphopeptides by zirconium phosphonate on self-assembled monolayers.

The dynamic range and low stoichiometry of protein phosphorylation frequently demands the enrichment of phosphorylated peptides from protein digests prior to mass spectrometry. Several techniques have been reported in literature for phosphopeptide enrichment, including metal oxides such as TiO(2) and ion metal affinity chromatography (IMAC). While the metal oxides have been used with reasonable success, IMAC has suffered from reduced selectivity and poor reproducibility. In this report, we present the first demonstration of the use of immobilized zirconium on a phosphonate-terminated self-assembled monolayer (SAM) for specific phosphopeptide capture and direct analysis by MALDI MS. By using the herein described functionalized-surface-based technology, efficient enrichment of phosphopeptides in different standard test systems such as alpha- or beta-casein digests or synthetic phosphopeptides spiked in nonphosphorylated protein digest has been demonstrated. The limit of detection for a beta-casein phosphopeptide was assessed to be at the low femtomole level. Compared to other state-of the-art technologies, like use of TiO(2) and Fe-IMAC, the presented technique demonstrated a superior performance with respect to specificity and bias with respect to singly or multiply phosphorylated peptides. Additionally, this platform was also successfully applied for ESI sample preparation, providing detailed sequence information of the investigated phosphopeptide. This technology was also proven to be applicable for real life samples such as phosphorylation site analysis of recombinant human MAPK1 and HSP B1 isolated from a 2D-gel spot by phosphopeptide enrichment and direct MALDI MS/MS.