Speaker
Description
Conventional condensed-phase bioanalytical approaches often require large amounts of high-purity samples and are, therefore, not universally applicable. Mass spectrometry (MS), on the other hand, requires only minute sample amounts and its purity is often not a critical factor. Although, the extent of structural information obtained directly by MS is limited,it can be combined with complementary techniques, such as ion-mobility mass spectrometry (IM-MS) and gas-phase infrared (IR) spectroscopy to yield both conformational- (IM-MS) and vibrational information (IR) on the molecules of interest.
Here, we report on the combination of IM-MS and cryogenic IR spectroscopy. Biomolecules are transferred to the gas phase under soft conditions by nano-electrospray ionisation and are separated based on their size, mass, and charge in a linear drift tube by collisions with an inert buffer gas followed by a quadrupolar mass analyser. Based on the arrival time of the molecules travelling through the drift tube, different conformations of molecules can be isolated and selected for the transfer to the cryogenic ion trap. In the trap, ions are cooled to ~40 K and tagged with weakly-bound neutral N2 molecules. When such tagged ions absorb one (or more) IR photons from a benchtop OPO/OPA laser or the FHI free electron laser, the tag can dissociate from the ion, which leads to a mass shift of the analyte in the time-of-flight mass analyser. Finally, the IR spectrum of mass- and conformer-selected ions is recorded by monitoring the signal of the tagged (or untagged) ion in the time-of-flight mass spectrum as a function of excitation wavelength. To demonstrate the wide-range applicability of the instrument, vibrational data have been collected from a wide range of biomolecular species, such as peptides and carbohydrates.
