Mass Spectrometer: FT-ICR, 6T (Ion Surface Collisions)
- Incorporate SID
- Equipped with ESI and MALDI
- 6-Tesla magnet
The 6-Tesla High-Field Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS), is a unique instrument designed and constructed at EMSL. It was designed to incorporate surface-induced dissociation (SID) as an excitation method for complex ions. The instrument is equipped with a high-transmission electrospray ionization source (ESI) and an intermediate pressure matrix assisted laser desorption ionization (MALDI) source for efficient ionization of large molecules. The ESI source consists of an ion funnel, a mass-resolving quadrupole, and an external ion accumulation cell. Ions are transferred to the ICR cell by a series of electrostatic lenses and impacted orthogonally on a surface. The SID surface is introduced to the rear trapping plate of the ICR cell using a probe vacuum-lock system. The kinetic energy of projectile ions is varied by floating the surface and the ICR cell off ground potential. This is achieved through a capacitive coupling of the excitation/detection plates of the cell to a DC power supply. This approach eliminates defocusing of the ion beam by the ion transfer optics as kinetic energy is varied. Consequently, ion current on the surface is independent of collision energy. The instrument is controlled by a MIDAS data station.
Surface-induced dissociation provides an efficient means of activation and dissociation of large molecules. Ion activation by collision with a surface is advantageous because large amounts of energy can be easily deposited into a molecule in a very short time (<10-12 s). Furthermore, eliminating the introduction of collision gas into the ICR cell for collisional activation and removing it prior to mass analysis dramatically shortens the acquisition time for MS/MS experiments. We have demonstrated that low-energy SID in FT-ICR MS yields fragmentation spectra comparable to multiple-collision activation conventionally utilized in MS/MS experiments. At higher collision energies SID opens up a variety of dissociation channels that are not accessible by slow activation methods. This allows good sequence coverage to be obtained even for those large ions that are difficult to fragment using other activation techniques. In addition, long and variable reaction time (milliseconds to seconds) characteristic of a trapping device greatly reduces the kinetic shift and allows both observing fragmentation at relatively low collision energies and studying the lifetime effect on the dissociation pattern of large ions.
- Kinetics of peptide fragmentation
- Energetics and mechanisms of peptide fragmentation
- Dynamics of ion-surface interaction and energy transfer in collisions
- Soft landing and neutralization of ions on surfaces.
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