Abstract
Imidazole (IMI) is a basic building block of many biologically important compounds. Thus, its electron ionization properties are of major interest and essential for the comparison with other molecular targets containing its elemental structure. 2-Nitroimidazole (2NI) contains the imidazole ring together with nitrogen dioxide bound to the C2 position, making it a radiosensitizing compound in hypoxic tumors. In the present study, we investigated electron ionization of IMI and 2NI and determined the mass spectra, the ionization energies, and appearance energies of the most abundant fragment cations. The experiments were complemented by quantum chemical calculations on the thermodynamic thresholds and potential energy surfaces, with particular attention to the calculated transition states for the most important dissociation reactions. In the case of IMI, substantially lower threshold values (up to ~ 1.5 eV) were obtained in the present work compared to the only available previous electron ionization study. Closer agreement was found with recent photon ionization values, albeit the general trend of slightly higher values for the case of electron ionization. The only exception for imidazole was found in the molecular cation at m/z 40 which is tentatively assigned to the quasi-linear HCCNH+/ HCNCH+. Electron ionization of 2NI leads to analogous fragment cations as in imidazole, yet different dissociation pathways must be operative due to the presence of the NO2 group. Regarding the potential radiosensitization properties of 2NI, electron ionization is characterized by dominant parent cation formation and release of the neutral NO radical.
Highlights
Radiation is a major source of damage for intact cells [1, 2]
The present study revealed the reactions in imidazole and 2nitroimidazole upon electron ionization
Since imidazole is a basic building block of life and dedicated derivatives based on the nitroimidazole group are already used as radiosensitizers in radiation therapy and as antibiotics, this knowledge is crucial to understand the basic reactions occurring under electron interactions mainly those yielding ionization processes
Summary
Radiation is a major source of damage for intact cells [1, 2]. It is widely used in radiotherapy to kill tumor cells. The drawback of the radiation is that healthy tissue may be damaged. The lack of selectivity is addressed by radiosensitizers, increasing the ratio of damage of malignant to healthy cells [3, 4]. One problem is to overcome hypoxia, which is common in many cancerous tissues [5, 6].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the American Society for Mass Spectrometry
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
