Abstract

Purpose

To clarify the radiosensitization mechanism masking the Auger effect of the cells possessing brominated DNA, the electronic properties of DNA-related molecules containing Br were investigated by X-ray spectroscopy and specific heat measurement.

Materials and Methods

X-ray absorption near-edge structure (XANES) and X-ray photoemission spectroscopy (XPS) were used to measure the electronic properties of the nucleotides with and without Br. We determined the specific heat of 5-bromouracil crystals with thymine as a reference molecule at low temperatures of 3–48 K to calculate the microscopic state numbers.

Results

Obtained XANES and XPS spectra indicated that both the lowest unoccupied molecular orbital (LUMO) and the core-levels were not affected by the Br incorporation. The state numbers of 5-bromouracil calculated from the specific heats obtained around 25 K was about 1.5 times larger than that for thymine below 20 K, although the numbers were almost the same below 5 K.

Discussion

Our results suggest that the Br atom may not contribute substantially to the LUMO and core-level electronic states of the molecule, but rather to the microscopic states related to the excitation of lattice vibrations, which may be involved in valence electronic states.

中文翻译：

---

含溴原子的DNA相关分子的电子特性

摘要

目的

为了阐明掩盖具有溴化 DNA 的细胞的俄歇效应的放射增敏机制，通过 X 射线光谱和比热测量研究了含 Br 的 DNA 相关分子的电子特性。

材料和方法

X 射线吸收近边结构 (XANES) 和 X 射线光电子能谱 (XPS) 用于测量含和不含 Br 的核苷酸的电子特性。我们在 3-48 K 的低温下以胸腺嘧啶作为参考分子测定了 5-溴尿嘧啶晶体的比热，以计算微观状态数。

结果

获得的 XANES 和 XPS 光谱表明最低未占分子轨道 (LUMO) 和核心能级均不受 Br 掺入的影响。从 25 K 附近获得的比热计算的 5-溴尿嘧啶的态数比 20 K 以下的胸腺嘧啶的态数大约大 1.5 倍，尽管在 5 K 以下的态数几乎相同。

讨论

我们的结果表明，Br 原子可能对分子的 LUMO 和核心能级电子态没有实质性贡献，而是对与晶格振动激发相关的微观状态有贡献，这可能与价电子态有关。