Reference : Probing the conformational changes during desolvation of ions using orthogonal mobili...
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Probing the conformational changes during desolvation of ions using orthogonal mobility methods (CE-IMS)
Far, Johann mailto [Université de Liège > Chemistry > Laboratoire de spectrométrie de masse (L.S.M.) > Ph.D >]
Kune, Christopher mailto [Université de Liège > Département de chimie (sciences) > Laboratoire de spectrométrie de masse (L.S.M.) >]
Delvaux, Cédric mailto [Université de Liège > Département de chimie (sciences) > Laboratoire de spectrométrie de masse (L.S.M.) >]
De Pauw, Edwin mailto [Université de Liège > Département de chimie (sciences) > Laboratoire de spectrométrie de masse (L.S.M.) >]
24th International Conference on Ion Mobility Spectrometry
du 26 juillet 2015 au 30 juillet 2015
International Society of Ion Mobility Spectrometry (ISIMS)
[en] conformational change ; capillary electrophoresis ; ion mobility spectrometry ; electrospray
[en] The transfer of ions from the solution to the gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find a new equilibrium conformation in the gas phase. The pathway to reach the thermodynamically stable conformation involves crossing potential barriers of different heights. When these barriers are too high compared to the internal energy of the ions, it will result in “partial memories” (as structural preservation) of the conformation in solution.
In order to evaluate the effect of the solvent evaporation and of the various collision processes encountered by the ions in the mass spectrometer, we developed two strategies:
The first strategy consists in comparing in a single experiment the shape of the ions in solution and in the gas phase. Data are obtained by coupling capillary electrophoresis with Ion Mobility Mass Spectrometry. Drift times in solution and in the gas phase are directly compared. Deviations from their correlation points out changes in folding upon desolvatation. Preliminary results show that among peptides issued from tryptic digest of BSA some of them clearly change their conformation during desolvatation.
The second strategy consists in probing changes of conformation once the ions are in the gas phase. The ions are rapidly heating by collisions ions during their transfer to the IMS. The heating is obtained by increasing their collision energy, rapidly followed by thermalisation in the IMS cell. The ions may be kinetically trapped in their new conformations. This allows comparing barriers between different ions geometries.
In summary this work intends to evaluate the extent of conformational “memory” of the ions of different nature for best experimental condition allowing “native mass spectrometry”
Laboratoire de spectrométrie de masse
Laboratory of Mass Spectrometry (LSM, ULG), Analis S.A (Namur, BE)
Researchers ; Professionals ; Students
Evaluation of the « nativity » of biopolymers studied using Mass Spectrometry (MS) by comparison of mobility values between gas and liquid phases.
Ion Mobility (IM) leads to mobility constant in gas phase when Capillary electrophoresis (CE) provides the mobility constant in liquid phase.
Both techniques can evaluate the tridimensional shape of ions from the mobility value.
During « Native MS » studies, the charges of ions are due to:
- Electrospray source parameters and ions source design during the desolvatation processes,
- The pH value of the liquid phase (background electrolyte, BGE) when weak electrolytes are considered.
Before desolvatation (in solution), the shape of ion is estimated by CE (coupled with MS) in various liquid phase (BGE) such as physiologic buffer or more denaturant liquid phase.
After desolvatation the shape of ions in softer ESI MS condition is evaluated during IM experiments (with the support of computational chemistry such as Density Functional Theory and Molecular Dynamics).
Correlation of the mobility data between IM and CE will be attempted.

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