Energy-dependent selective bond cleavage induced by low-energy electrons in DNA films deposited from buffered solutions: Insights from XPS

In this study, we investigated chemical modifications caused by low-energy electrons (LEEs) in DNA films deposited from Tris-EDTA (TE) buffered solutions, using x-ray photoelectron spectroscopy (XPS). DNA samples were exposed to 9.2, 4.2, and 0.2 eV electrons for up to 8 h. XPS revealed the energy- and site-specific selective cleavage of chemical bonds as observed in C 1s, N 1s, O 1s, and P 2p spectra. At 9.2 and 4.2 eV, LEE irradiation significantly induced the cleavage of C-N bonds in N-glycosidic linkages and C-O bonds in the sugar-phosphate backbone. The selective cleavage of C-N and C-O bonds may lead to the generation of apurinic/apyrimidinic sites and produce damage to the sugar-phosphate backbone and sugar moiety. In contrast, other structures, including the phosphate groups (P=O) within the DNA backbone, remained relatively stable. Non-significant spectral or compositional changes were observed at 0.2 eV. The TE components remain chemically stable during irradiation; however, experimental results suggest that it may help increase the yield of selective DNA damage. Our findings contribute to a deeper mechanistic understanding of LEE-induced biomolecular damage and support the development of LEE-based cancer radiotherapy.