Dissociative electron attachment to the radiosensitizing chemotherapeutic agent hydroxyurea

Dissociative electron attachment to hydroxyurea was studied in the gas phase for electron energies ranging from zero to 9 eV in order to probe its radiosensitizing capabilities. The experiments were carried out using a hemispherical electron monochromator coupled with a quadrupole mass spectrometer. Diversified fragmentation of hydroxyurea was observed upon low energy electron attachment and here we highlight the major dissociation channels. Moreover, thermodynamic thresholds for various fragmentation reactions are reported to support the discussion of the experimental findings. The dominant dissociation channel, which was observed over a broad range of energies, is associated with formation of NCO−, water, and the amidogen (NH2) radical. The second and third most dominant dissociation channels are associated with formation of NCNH− and NHCONH2 −, respectively, which are both directly related to formation of the highly reactive hydroxyl radical. Other ions observed with significant abundance in the mass spectra were NH2 −/O−, OH−, CN−, HNOH−, NCONH2 −, and ONHCONH2 −.