【作者】 陈亮；

【导师】 盛六四；

【作者基本信息】 中国科学技术大学 ， 同步辐射及应用， 2011， 博士

【摘要】 因在辐射损伤的风险评估以及辐射防护等领域有着广泛的用途,X射线的辐射生物学效应一直受到科研工作者的关注。这其中具有较高线性能量衰减系数的低能软X射线更受到重视,就其原因,一方面低能X射线具有中等的线能传递系数,在细胞内能产生较高的能量衰减;同时低能软X射线与物质作用的主要形式为光电吸收,在细胞内产生大量的光电子并伴生俄歇电子。这些二次电子具有纳米的轨道径迹和局部能量高度沉积等特点,可造成细胞内大分子物质结构的破坏,进而造成细胞的辐射损伤,其损伤效应要高于高能硬X射线以及60Co-γ射线,并随着X射线能量的降低,其辐射损伤效应有增加趋势。将同步辐射软X射线应用于对生物细胞的辐射损伤效应的研究是近年来的一个研究热点。同步辐射具有亮度高、能量连续可调等优势,将其引入细胞辐射效应的研究,不仅可以获得高强度的X射线,在较短时间内可实现对较多细胞的照射,使实验结果更具有统计学意义,而且利用同步辐射,可以实现选择能量的照射,研究不同能量X射线的辐射损伤特异性,并且可以对细胞具有相同穿透能力的不同能量软X射线对细胞的辐射损伤的差异进行比较,实现在不同层面进行软X射线的辐射损伤效应研究。对于同步辐射来说,“水窗”波段软X射线是其辐射的特点,也是其优势。“水窗”波段软X射线为低能X射线,其与细胞作用时产生大量的光电子和俄歇电子,同时细胞的主要组成元素C、N、O的K吸收边均位于该波段内。当以元素吸收边能量X射线照射细胞时,由于共振吸收,在细胞内产生很强的剂量沉积,因而其辐射损伤可能会更强。针对同步辐射软X射线所具有的特点,以合肥弯铁辐射为辐射源,采用波带片色散单色技术,将同步辐射光单色化,获得低能软X射线,对“水窗”波段软X射线的辐射损伤的特性,从不同吸收边能量、吸收边附近能量的辐射损伤差异的比较、元素吸收边能量的辐射损伤增强效应,从射线照射至细胞核损伤、细胞死亡、变异、射线至细胞不同部位的辐射损伤差异等几个方面进行了比较研究。同时,利用同步辐射红外光谱分析和检测技术以及生物学的凝胶电泳技术对一些影响因素及辐射结果进行分析、检测和讨论,研究“水窗”波段不同能量软X射线的辐射损伤特异性。研究结果表明,同步辐射“水窗”波段软X射线对生物细胞具有较强的辐射损伤效应,其辐射损伤效应要高于60Co-γ射线的辐射损伤效应,且在该波段,其辐射损伤效应随着X射线能量增加有增加趋势,同时位于元素吸收边能量的软X射线的辐射损伤效应也存在不同,这些都显示出“水窗”波段软X射线的辐射损伤特异性。更多还原

【Abstract】 As is valuable radiation damage in risk evaluation and radiation protection, the radiobiological studies of X-ray are attracted for attentions in these years, and even more, soft X-rays, which have higher linear energy attenuation coefficients, have attracted more interesting. For the reasons, firstly, as low energy rays, the main is photon-electron absorption when soft X-rays interacting with matter and large numbers of photoelectrons, also combining with large numbers of Auger electrons, and there second electrons have track path with nanoscale and can deposit energies in small space, which can cause the structure damage of macromeolecule in cells, thus can cause radiation damage in cells. At the same time, the effect of radiation damage is increasing with the X-ray energy decreasing and is more higher than that of hard X-rays and 60Co-γrays.Using soft X-rays from synchrotron radiation are valuable for radiobiological studies. The synchrotron radiation has many valuable characteristics, such as have high radiation flux and the radiation energy can be adjusted continuously. When using synchrotron radiation as the radiation source, the higher radiation fluxes can be obtained and more samples can be treated each time, and thus the experimental results can be more suitable for statistical principle. At the same time, with the help of synchrotron radiation, the radiation damage studied with selected energies can come true and thus the radiation damage with different energies can be studied. Also the radiation effects of soft X-rays with different energies, which have similar transmission abilities in cells, can be compared, thus the radiobiological effects of soft X-rays at different layer can be studied.As with other radiation source, the X-rays at“water window”region have their unique characteristics and also an advantage for synchrotron radiation. The X-rays at“water window”region are low energy rays and large numbers second electrons are produced in cells when transmitting through cells. At the same time, the K-shell absorption edges of C, N, O elements, which are also the main composing elements of biological cells, are all in this region. When cells irradiated with soft X-rays at the K-shell edges of those elements, more dose will be deposited in cells because of resonance absorption and the radiation damage may be more serious.Considering the specialties of soft X-rays from synchrotron radiation, using the bending magnet radiation of Hefei synchrotron radiation as the radiation source and the zone plate as dispersively optical element, the synchrotron radiation was monochromated and the radiation damage characteristic of soft X-rays at“water window”was studied, including different energies irradiating, the radiation damage discrepancy of soft X-rays near the absorption edges and the radiation damage enhancement of X-rays at the K-shell edges, etc. The studies included soft X-rays causing nucleolus radiation damage, cell killing, mutating and the difference of different compartments of cells. At the same time, the infrared spectrum of synchrotron radiation and gel electrophoresis technique were used as valuable tools for radiation results detecting and analyzing, and also for some influence factors discussing. The peculiar radiation damage of soft X-rays with different energies at“water region”was studied.The experimental results showed that soft X-rays at“water window”region have high radiation damage abilities, and the radiobiological effects are higher than that of 60Co-γrays and the radiation increases with the X-ray energies increasing. At the same time, the radiation effects of X-rays at the K-shell absorption edges are also different. All these indicate that soft X-rays at“water window”region have peculiar radiation damage effects.更多还原