Abstract
To identify the precise early radiation processes of DNA lesions, we measure electron kinetic energy spectra emitted from uridine-5′ monophosphate (UMP) in aqueous solution for the photoionization of the N 1s orbital electron and for the following Auger effect using a monochromatic soft X-ray synchrotron radiation at energies above the nitrogen K-shell ionization threshold. The change of photoelectron spectra for UMP in aqueous solutions at different proton concentrations (pH = 7.5 and 11.3) is ascribed to the chemical shift of the N3 nitrogen atom in uracil moiety of canonical and deprotonated forms. The lowest double ionization potentials for aqueous UMP at different pH obtained from the Auger electron spectra following the N 1s photoionization values show the electrostatic aqueous interaction of uracil moiety of canonical (neutral) and deprotonated (negatively charged) forms with hydrated water molecules.
Highlights
DNA lesions induced by ionizing radiation can be the cause of cancers, cell deaths and mutations
In the radiation interaction with DNA, the cross sections for outer shell excitation are large enough to absorb the energy of ionizing radiation efficiently, yet outer-shell excitation and ionization mainly induce single strand breaks of DNA at most, which are reparable by repair enzyme proteins
We have shown the selective excitation of the nucleobase moieties of nucleotides in aqueous solutions by measuring the X-ray absorption near-edge structure (XANES) spectra at energies in the vicinity of the nitrogen K-edge [8,9,10]
Summary
DNA lesions induced by ionizing radiation can be the cause of cancers, cell deaths and mutations. We revealed aqueous interaction onto the biding energies of nitrogen K-shell orbital electrons of nucleobase moieties as a result of the structural change between the imine (double-bonded –N=) and amine (single-bonded –N
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