Post-translational modifications of proteins are key regulatory events for cellular systems, where proteins are covalently modified through addition of functional groups, such as phosphoryl or glycosyl groups, or cleavage events. These modifications can alter the structure and function of proteins, which can affect the role of proteins in biological systems. PTMS can usually be detected easily by mass spectrometry due to a change in peptide mass based on the type of modification, though this does not always yield site specific information. The specificity of the type and position of the modification and produce very different effects on protein function, hence the ability to specifically identify PTMs sites is crucial to understanding how these modifications affect protein function.
Ion mobility enables the separation of isomeric peptides and proteins that may be otherwise indistinguishable by traditional LC-MS. Furthermore, the cyclic ion mobility instrument allows for unique MSn experiments, where species can be separated by IMS, selected and re-injected for further IMS separation. This enables very selective experiments, speciation of PTMs and in-depth characterisation of proteins and peptides. Here, we demonstrate the capacity for cIMS to separate, characterise and identify a range of common PTMS, including phosphorylation and glycosylation, in both simple and complex mixtures. The ability to more clearly separate and characterise PTMs will enable greater insight into the role these moieties play in biological systems.