Two-Parameter Power Formalism for Structural Screening of Ion Mobility Trends: Applied Study on Artificial Molecular Switches.

Recent literature provides increasing samples of structural studies relying on ion mobility coupled to mass spectrometry in view of characterizing gas-phase conformation and energetics properties of biomolecular ions. A typical framework consists in experimentally monitoring the collisional cross sections for various experimental conditions and using them as references to select appropriate candidate structures issued from theoretical modeling. Although it has proved successful for structural assignment, this process is resource costly and lengthy, namely due to intricacies in the selection of appropriate input geometries. In the present work, we propose simplified methodologies dedicated to the systematic screening of ion mobility data acquired on systems built from repetitive subunits and detail their application to challenging artificial molecular switch systems. Capitalizing on coarse-grained design, we first demonstrate how the assimilation of subunits into adequately assembled building-blocks can be used for fast assignments of a system topology. Further focusing on topology-specific differential ion mobility trends, we show that the building-block assemblies can be fused into single fully convex solid figure models, i.e., sphere and cylinder, whose projected areas follow a two-parameter power formalism A × nB. We show that the fitting parameters A and B were assigned as structural descriptors respectively associated with the dimensions of each constitutive subunit, i.e., size parameter, and with their assembled tridimensional arrangement, i.e., shape parameter. The present work provides a ready-to-use method for the screening of IM-MS data sets that is expected to facilitate the eventual design of input structures whenever advanced modeling calculations are required.