High Resolution Capillary Isoelectric Focusing Mass Spectrometry Analysis of Peptides, Proteins, And Monoclonal Antibodies with a Flow-through Microvial Interface
Wang, LY (Wang, Lingyu)[ 1,2 ] ; Bo, T (Bo, Tao)[ 3 ] ; Zhang, ZX (Zhang, Zhengxiang)[ 3 ] ; Wang, GB (Wang, Guanbo)[ 1 ] ; Tong, WJ (Tong, Wenjun)[ 1 ]*（童文骏）; Chen, DD (Chen, David Da Yong)[ 1,2 ]*
[ 1 ] Nanjing Normal Univ, Sch Chem & Mat Sci, Nanjing 210023, Jiangsu, Peoples R China
[ 2 ] Univ British Columbia, Dept Chem, Vancouver, BC V6T 1Z1, Canada
[ 3 ] Thermo Fisher Sci, 7th Floor,Bldg F,Tower West,Yonghe Plaza, Beijing 100007, Peoples R China
Capillary isoelectric focusing directly coupled to high resolution mass spectrometry (cIEF-MS) provides information on amphoteric molecules, including isoelectric point and accurate mass, which enables structural interrogation of biopolymer pI variants. The coupling of cIEF with MS was facilitated by a flow through microvial interface, made by stainless steel with high chemical resistance and mechanical robustness. Two on-column electrolyte configurations of cIEF-MS were demonstrated using peptide and protein pI markers. The pI resolution was 0.02 pH unit in the pH range of S.S to 7.0, with no anticonvective reagent (glycerol) added. High resolution Orbitrap detector provides mass spectra for midsized proteins (<30 kDa), enabling deconvolution with high accuracy for IEF-focused low abundance species. Charge heterogeneity of therapeutic monoclonal antibodies (mAb) is one of the most important attributes in the biopharmaceutical industry, and it is routinely monitored by IEF and fractionation-based methods. As a proof of concept, the commercial formulation of infliximab was directly analyzed using cIEF-MS for separation and online identification of mAb charge variants. The main intact antibody species along with two basic and one acidic variants were observed, and their accurate molecular weights (M-W) recorded by MS detector readily revealed the structural differences of these variants. Variants with 0.1 unit in pI difference and 1 Da difference in molecular weight were readily resolved. The deconvoluted intact M-W values showed ppm level accuracy compared to theoretical predictions.