• Egorov, D.; Bari, S.; Boll, R.; Dörner, S.; Deinert, S.; Techert, S.; Hoekstra, R.; Zamudio-Bayer, V.; Lindblad, R.; Bülow, C.; Timm, M.; von Issendorff, B.; Lau, J.T.; Schlathölter, T.: Near-Edge Soft X-ray Absorption Mass Spectrometry of Protonated Melittin. Journal of The American Society for Mass Spectrometry 29 (2018), p. 2138–2151

Open Accesn Version

We have investigated the photoionization and photofragmentation yields of gas-phase multiply protonated melittin cations for photon energies at the K-shell absorption edges of carbon, nitrogen, and oxygen. Two similar experimental approaches were employed. In both experiments, mass selected [melittin+qH]q+ (q=2–4) ions were accumulated in radiofrequency ion traps. The trap content was exposed to intense beams of monochromatic soft X-ray photons from synchrotron beamlines and photoproducts were analyzed by means of time-of-flight mass spectrometry. Mass spectra were recorded for fixed photon energies, and partial ion yield spectra were recorded as a function of photon energy. The combination of mass spectrometry and soft X-ray spectroscopy allows for a direct correlation of protein electronic structure with various photoionization channels. Non-dissociative single and double ionization are used as a reference. The contribution of both channels to various backbone scission channels is quantified and related to activation energies and protonation sites. Soft X-ray absorption mass spectrometry combines fast energy deposition with single and double ionization and could complement established activation techniques.