Fujii Kentaro, Akamatsu Ken, Yokoya Akinari
Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Sayo, Hyogo 679-5148, Japan.
Radiat Res. 2004 Apr;161(4):435-41. doi: 10.1667/rr3131.
Positive ion desorption from thin films of DNA components, 2-deoxy-d-ribose, thymine, thymidine (dThd), and thymidine 5'-monophosphate (dTMP) was investigated in the oxygen K- shell edge excitation region using synchrotron ultrasoft X rays (538 eV). A large number of molecular fragments, H(+), CH(x)(+), C(2)H(x)(+), CO(+), CH(x)O(+), C(3)H(x)(+), C(2)H(x)O(+) and C(3)H(x)O(+) (x = 1, 2 and 3), were observed as desorbed ions from 2-deoxy-d-ribose. Some of these ions are related to simultaneous bond scission at particular C-C and C-O (or C-C) bonds in the furanose ring structure in the 2-deoxy-d-ribose molecule, indicating that the impact of photons on the oxygen atom and the impact of ejected secondary electrons (e.g. Auger electrons) cause an intense destruction of the furanose ring structure. In thymine thin films, H(+), CH(x)(+), CO(+), CH(x)O(+), C(2)H(x)N(+) and CH(x)NO(+) (x = 1, 2 and 3) fragments were observed. The yields of these ions were smaller than the yields from 2-deoxy-d-ribose. The desorption of CH(3)(+) from thymine might induce a molecular conversion from thymine to uracil. The mass patterns of dThd and dTMP, and especially that of dTMP, were similar to that of 2-deoxy-d-ribose, indicating that a number of ions were generated at the sugar site, even in the nucleotide molecule. It is therefore predicted that the sugar moiety is more fragile than the thymine base.
利用同步加速器超软X射线（538电子伏特），在氧K壳层边缘激发区域研究了DNA成分薄膜、2-脱氧-D-核糖、胸腺嘧啶、胸苷（dThd）和胸苷5'-单磷酸（dTMP）的正离子解吸。观察到大量分子碎片，H(+)、CH(x)(+)、C(2)H(x)(+)、CO(+)、CH(x)O(+)、C(3)H(x)(+)、C(2)H(x)O(+)和C(3)H(x)O(+)（x = 1、2和3），作为从2-脱氧-D-核糖解吸的离子。这些离子中的一些与2-脱氧-D-核糖分子中呋喃糖环结构中特定C-C和C-O（或C-C）键的同时断裂有关，这表明光子对氧原子的撞击以及射出的二次电子（如俄歇电子）的撞击会导致呋喃糖环结构的强烈破坏。在胸腺嘧啶薄膜中，观察到H(+)、CH(x)(+)、CO(+)、CH(x)O(+)、C(2)H(x)N(+)和CH(x)NO(+)（x = 1、2和3）碎片。这些离子的产率低于2-脱氧-D-核糖的产率。胸腺嘧啶中CH(3)(+)的解吸可能会诱导胸腺嘧啶向尿嘧啶的分子转化。dThd和dTMP的质谱图，尤其是dTMP的质谱图，与2-脱氧-D-核糖的质谱图相似，这表明即使在核苷酸分子中，也有许多离子在糖位点产生。因此可以预测，糖部分比胸腺嘧啶碱基更脆弱。
