Here, the development of a hybrid technology built on mass spectrometry (MS) of intact assemblies, ion-mobility and proteomics to study the structural assembly process of protein complexes is proposed. Research on higher order assemblies is often frustrated by their low abundance and heterogeneity. Increasingly, MS of intact protein assemblies is emerging as an approach for determining dynamical protein complex organization and architecture. But this approach is limited by the complexity of the assemblies that can be solved by native MS alone due to ambiguities in assigning masses to unique subunit stoichiometries. Proteomic methods on the other hand are able to identify precisely all proteins present but cannot reveal the integration and stoichiometry of subunits within different sub complexes. These techniques are complementary to each other and a hybrid MS platform seems uniquely suited to generate structural data of dynamic protein assemblies. The research suggested in this proposal is focused on the generation of the necessary technological tools to investigate this question. This integrated platform will be implemented to investigate the complete assembly pathway of the anaphase promoting complex, to monitor cell cycle dependant changes in its subunit composition and to identify the overall network of proteins involved in complex assembly.