Mechanisms of molecular changes in amino acids due to inner shell ionization

据报道，当与组成原子的吸收边缘相对应的单色软x射线照射时，放射生物学效应增强。我们一直在研究这种增强机制。在本研究中，我们研究了单色软x射线照射含硫氨基酸在硫k壳吸收边缘附近的分子变化机制，期望这可能是生物增强的潜在机制。研究结果总结如下：a)包括内壳电离原子在内的共价键比其他键更有效地劈裂。b)碳硫键不仅对硫的光吸收敏感，而且对其他组成原子的光吸收也敏感。c)在水溶液中辐照时，可以观察到碎片的OH加合物。d)硫碳键的裂解效率不受OH自由基清除剂加入的影响，说明硫碳键的裂解主要是通过辐射的直接作用进行的。由于我们无法鉴定HPLC图中观察到的所有片段，我们正在考虑使用放射性同位素示踪剂等新的鉴定方法。

It was reported that the radiobiological effects are enhanced when monochromatic soft X-rays corresponding to the absorption edges of the constituent atoms are irradiated. We have been studying this enhancement mechanism. In this research, we investigated the mechanisms of molecular changes of sulfur-containing amino acids irradiated with monochromatic soft X-rays around sulfur K-shell absorption edge, expecting that this might be a underlying mechanism of the biological enhancement.Research results are summarized as follows.a)Covalent bonds including the inner shell ionized atom are cleaved more effectively than the other bonds.b)Carbon-sulfur bonds are sensitive not only to the photoabsorption of sulfur but also to that of the other constituent atoms.c)When irradiated in aqueous solution, OH adducts of the fragments are observed.d)Cleavage efficiency of the sulfur-carbon bond is not affected by the addition of OH radical scavenger, indicating that cleavage of the bond mainly occurs via direct action of the radiation.Since we could not identify the all fragments observed in the HPLC chart, we are considering new identification methods such as the use of radioisotope tracers.