X-ray photoelectron spectroscopy of Thymine and 5-Bromouracil studied by Symmetry-Adapted-Cluster Configuration-Interaction (SAC-CI) theory

Incorporation of a bromine atom into DNA-related molecules changes their electronic properties

“…16 All the N 1s binding energies listed in Table 1 are 400.23 eV because this energy was used for energy calibration based on the report by Plekan et al 13 The O 1s binding energies were consistent with those reported by Plekan et al 13 The peaks for the N and O atoms were also investigated by the SAC-CI calculations. 16…”

“…Note that the SAC-CI calculations revealed that the C 1s spectra of T are composed of five peaks. 16 All the N 1s binding energies listed in Table 1 are 400.23 eV because this energy was used for energy calibration based on the report by Plekan et al 13 The O 1s binding energies were consistent with those reported by Plekan et al 13 The peaks for the N and O atoms were also investigated by the SAC-CI calculations. 16 The wide-scan XPS spectra (EB: 1900-0 eV) of BrdU and dT are shown in Fig.…”

“…The origin of the four peaks was elucidated by the SAC-CI calculations. 16 The 1s binding energies of other atoms are listed in Table 1. The peak splitting of C (I) and (II) in the C 1s spectrum of T (3.3 eV) was significantly broader than that for BrU (2.7 eV), indicating that the Br atom may affect the core level energy of the Br–C bond.…”

“…We have already calculated the XPS of T and BrU by the SAC-CI method, and theoretically assigned the peaks of the spectra. 16…”

“…Photoelectron peaks assigned to the inner-shell levels of each element were observed (BrU: bromine [Br] 2p3/2, Br 2p1/2, oxygen [O] 1s, nitrogen [N] 1s, and carbon [C] 1s; T: O 1s, N 1s, and C 1s), and these assignments were theoretically supported by the SAC-CI calculations. 16 No photoelectron signal from the aluminium substrate was observed, indicating that these spectra originated only from the sample molecules.…”