Selective excision of C5 from D-ribose in the gas phase by low-energy electrons (0-1 eV): Implications for the mechanism of DNA damage
Selective excision of C5 from D-ribose in the gas phase by low-energy electrons (0-1 eV): Implications for the mechanism of DNA damage
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DOI：
10.1002/anie.200600303
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Illenberger, Eugen
中科院分区：
文献类型：
--
作者：
Bald, Ilko;Kopyra, Janina;Illenberger, Eugen
糖是连接DNA碱基和磷酸基团的核苷酸的中心单位，磷酸基团本身与单链DNA中相邻的核苷酸偶联。对生物分子系统的激发、电离和碎裂的研究对于理解生命科学领域的许多问题是必不可少的，如细胞系统的辐射损伤机制或肿瘤治疗中使用的放射增敏剂的作用。高能辐射通过水或活细胞等致密介质时，会留下一丝自由电子。这些二次电子的数量(每兆电子能量为5？104)使它们成为最丰富的辐射分解物种。在热化过程中，它们可以诱导进一步的电离或激发过程，但它们也可以有效地以特定的能量(共振)和位置与DNA结合，形成随后解离的瞬时负离子(解离电子附着，DEA)。[2]充分的证据表明，DEA以其独特的特征在细胞DNA辐射分解的初始状态中发挥着重要作用。[2]到目前为止，这些现象已经在DNA复杂性的两个极端，即质粒DNA和气相中的分离碱基进行了研究。对质粒DNA的实验已经证明，低能电子可以有效地诱导单链断裂(SSB)和双链断裂(DSB)。[3]在极低能区(0-3 eV)，低于电子激发阈值，只观察到SSB。[4]在这些实验中，DSB和SSB的效率都明显地表现出与初级电子能量的函数关系，这表明负电子共振的形成是初始步骤。
Sugar is the central unit within a nucleotide connecting the DNA base with the phosphate group, which itself couples to the neighboring nucleotides within single-stranded DNA. The study of the excitation, ionization, and fragmentation of biomolecular systems is essential for the understanding of many problems in the area of life sciences such as the mechanism of radiation damage in cellular systems or the action of radiosensitisers used in tumor therapy. The passage of high-energy radiation through dense media such as water or a living cell leaves a trace of free electrons. These secondary electrons are created in numbers (5 î 104 per MeV of deposited energy [1]) that makes them the most abundant radiolytic species. In the course of thermalization they can induce further ionization or excitation processes, but they can also efficiently attach at specific energies (resonances) and sites to DNA, forming transient negative ions that subsequently dissociate (dissociative electron attachment, DEA).[2]Ample evidence exists that DEA with its unique features plays an important role in the nascent states of cellular DNA radiolysis.[2] To date, these phenomena have been investigated at two extremes of DNA complexity, namely, plasmid DNA and isolated nucleobases in the gas phase. Experiments on plasmid DNA have demonstrated that low-energy electrons can efficiently induce single-strand breaks (SSBs), as well as double-strand breaks (DSBs).[3] In the very low-energy domain (0–3 eV), below the threshold of electronic excitation, only SSBs are observed.[4] In these experiments it became apparent that the efficiency of both DSBs and SSBs as a function of the primary electron energy exhibits a resonant behavior, indicating that the formation of negativeion resonances is the initial step.