Deamidation Analysis of Biotherapeutic Proteins by Capillary Electrophoresis-Mass Spectrometry

Deamidation is a common chemical modification that can form spontaneously in solution and alter the chemistry of asparagine and glutamine residues. In biotherapeutics, uncontrolled deamidation poses a strong risk to product safety and efficacy. Traditional methods for assessing deamidation, such as ion-exchange chromatography and peptide mapping, can be limited. Capillary electrophoresis-mass spectrometry (CE-MS), in contrast, is well-suited for separating deamidated variants from their nondeamidated counterparts prior to identification by mass spectrometry (MS). For deamidation analysis, clear separation is critical for unambiguous MS identification as the variants can be shifted in mass by just 0.984 Da. In this chapter, a detailed method for the direct analysis of deamidation in protein biotherapeutics with CE-MS is outlined.