Speaker
Description
Over the last years, our team has employed a combination of electrospray ionization with radiofrequency ion guiding and trapping, to prepare targets of mass-selected trapped gas-phase biomolecular ions for photoexcitation/photoionization experiments using synchrotron, free electron laser or conventional laser beams [1] but also for collision experiment using MeV ions [2]. A recurrent problem in studies involving large molecular systems is the fact that they usually occupy a large conformational space, even under cryogenic conditions.
Conformationally separation of gas phase biomolecules has historically been achieved using drift tubes, where bunches of molecular ions drift through an inert gas under the influence of an electric field. The ion drift velocity can then be directly related to its geometric cross section. Typically however, these tubes need to be several meters long and require kV potentials which makes this approach problematic for interfacing with synchrotron or heavy ion beamlines where floorspace is limited and flexibility is required.
Figure 1: Photographs of the bottom printed circuit board of the travelling wave IMS system featuring DC guard electrodes, RF guiding electrodes and traveling wave pixels. Red arrows represent the direction of ion transport.
To overcome these issues our team has implemented an alternative ion-mobility approach based on radiofrequency ion guiding. Using the method pioneered by the Smith group at PNNL [3] the ions are guided by means of electrodes on a printed circuit board (see figure). This approach does not require high voltage gradients since the ions are transported using traveling waves. By using a serpentine path an overall pathlength of several meters can be collapsed into a compact instrument (see figure). This apparatus allows our team to produce m/q selected and conformationally pure beams of protonated and deprotonated biomolecular ions that can be easily interfaced with laser, synchrotron and MeV ion beamlines.
In the near future, we plan to use MeV carbon ions from the IRRSUD facility at GANIL/France to investigate collisions with conformer selected DNA.
References:
[1]: W. Li, O. Kavatsyuk, W. Douma, X. Wang, R. Hoekstra, D. Mayer, M. Robinson, M. Gühr, M. Lalande, M. Abdelmouleh, M. Ryszka, J.-C. Poully, T. Schlathölter, 2021 Chemical Science 12 13177
[2]: M. Lalande, M. Abdelmouleh, M. Ryszka, V. Vizcaino, J. Rangama, A. Méry, F. Durantel, T. Schlathölter, and J.-C. Poully, 2018 Physical Review A 98 062701
[3]: L. Deng, Y. M. Ibrahim, E. S. Baker, N. A. Aly, A. M. Hamid, X. Zhang, X. Zheng, S. V. B. Garimella, I. K. Webb, S. A. Prost, J. A. Sandoval, R. V. Norheim, G. A. Anderson, A. V. Tolmachev, R. D. Smith, 2016 ChemistrySelect, 1, 2396.
