A new tandem mass spectrometer for photofragment spectroscopy of cold, gas-phase molecular ions

Abstract

We present here the design of a new tandem mass spectrometer that combines an electrospray ion source with a cryogenically cooled ion trap for spectroscopic studies of cold, gas-phase ions. The ability to generate large ions in the gas phase without fragmentation, cool them to approximately 10 K in an ion trap, and perform photofragment spectroscopy opens up new possibilities for spectroscopic characterization of large biomolecular ions. The incorporation of an ion funnel, together with a number of small enhancements, significantly improves the sensitivity, signal stability, and ease of use compared with the previous instrument built in our laboratory.

Cryogenic Methods for the Spectroscopy of Large, Biomolecular Ions

“…Subsequent improvements to the Lausanne machine (Fig. 7) included the addition of an ion funnel to inject the electrosprayed ions more efficiently [131]. An instrument of similar design was more recently constructed in the group of Fuke and used to measure spectra of tryptophan-containing dipeptides [132] and their clusters with solvent [133].…”

Infrared Spectroscopy of Mobility-Selected H+-Gly-Pro-Gly-Gly (GPGG)

“…A schematic of the new instrument, which combines an ion mobility drift tube [34] with a cold ion trap [24,35] and a timeof-flight (TOF) mass spectrometer, is shown in Figure 2. Ions are produced using electrospray ionization and traverse the drift tube in a time that is proportional to their collisional crosssection [36].…”

“…Although a number of groups have developed experiments that couple mass spectrometry with infrared spectroscopy [21][22][23][24][25], the application of these experiments tends to be focused on relatively small molecules. This is because one cannot deduce a structure from the experimental data as directly as in the cases of nuclear magnetic resonance (NMR) or X-ray crystallography.…”

Conformation-Specific Spectroscopy of Peptide Fragment Ions in a Low-Temperature Ion Trap

“…Our experimental approach [45] has been described in detail elsewhere [57]. In brief, we produce protonated YGGFL ([YGGFL + H] + ) by nano-electrospray ionization from 50 or 100 μM solutions in 1/1 water/methanol mixtures, to which 0.1% of acetic acid is added.…”