Development and Use of Novel Instrumentation for Structural Analysis of Gaseous Ions

UoM administered thesis: Phd

  • Authors:
  • Jakub Ujma

Abstract

Traditional solution and solid state approaches (Nuclear Magnetic Resonance, X-Ray Crystallography) are methods of choice when analysing both biological and inorganic analytes. However, the characterisation of transient species, often encountered in self-assembling systems, is difficult. Such systems rarely produce crystals of high quality and due to their dynamic nature; their structures are difficult to study with NMR. Hyphenated gas phase methods which rely on mass spectrometry detection offer simultaneous structural analysis and direct stoichiometry measurement. As a consequence, it is possible to investigate specific, non-interacting molecules and molecular complexes in an isolated environment. This thesis focuses on the development and applications of two such methods - ion mobility mass spectrometry (IM-MS) and cold ion spectroscopy. IM-MS measurements yield a so called collisional cross sectional area (CCS). This parameter can be pictured as a rotationally averaged, shadow projection of a molecule structure. When correlated with the ion abundance, a CCS distribution yields intuitively interpretable information about the conformational preferences of an isolated molecule. Although indispensable in describing a "global" geometrical structure, the CCS parameter itself provides a limited insight into the local structural features of the assembly. Ion spectroscopy, both in the UV and IR regions, can provide an extra layer of highly descriptive information. Here, we present several cases where the above techniques have been applied. With the aid of IM-MS, we have analysed the geometry of inorganic supramolecular assemblies, highlighting the stability of particular metal-ligand interactions. Using cold ion spectroscopy, we have assessed the fine structural information of self-assembled oligomers of an amyloidogenic peptide. We correlated spectral features of isolated oligomers to features observed in the mature fibrils; therefore attempting to delineate the events in early stages of amyloidogenic aggregation. A major part of this report focusses on technological aspects of the design and development of a high resolution, variable temperature ion mobility mass spectrometer (VT-IM-MS). The thermal stability of molecules is a vital aspect in industrial process development and formulation science. Solution phase Differential Scanning Calorimetry (DSC) is a widely applied technique, allowing to monitor reversibility of thermally induced conformational transitions, a key aspect in protein folding analysis. The instrument reported here aims to provide parallel information about gaseous ions, with a particular focus on protein ions. Capabilities of the newly built instrument have been tested using small, rigid molecules, a small protein and a large multiprotein complex.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date1 Aug 2016