Capillary Electrophoresis Mass Spectrometry for Inositol (Pyro)phosphate Profiling

The turnover of myo-inositol phosphates (InsPs) and myo-inositol pyrophosphates (PP-InsPs) is a dynamic process that plays an important role in many physiological processes by transmitting signals within cellular pathways and networks. Profiling the InsPs and PP-InsPs isomers and quantifying their change in abundance is a significant challenge for several reasons. First, InsPs and PP-InsPs constitute a diverse metabolite pool, characterized by the complexity as a result of the numerous possible isobaric isomers. Second, these species are usually of low abundance in biological samples. Third, they lack a chromophore, making UV or fluorescence detection unfeasible. Fourth, their high charge density and the instability of P-anhydride bonds make isolation and separation requirements particularly demanding. This chapter presents a capillary electrophoresis coupled to mass spectrometry (CE-MS) method as a powerful tool. It enables the separation of multiply charged InsPs and PP-InsPs with high resolution for profiling regioisomers with high sensitivity from biological samples.