Department of Atomic and Molecular Physics , Manipal Academy of Higher Education , Manipal 576 104 , India.
Centre for Applied Nanosciences, Department of Atomic and Molecular Physics , Manipal Academy of Higher Education , Manipal 576 104 , India.
J Phys Chem A. 2020 Feb 27;124(8):1508-1514. doi: 10.1021/acs.jpca.0c00009. Epub 2020 Feb 14.
Electrons and OH-radicals have been generated by using low-energy laser pulses of 6 ns duration (1064 nm wavelength) to create plasma in a suspension of plasmid DNA (pUC19) in water. Upon thermalization, these particles induce single and double strand breakages in DNA along with possible base oxidation/base degradation. The time-evolution of the ensuing structural modifications has been measured; damage to DNA is seen to occur within 30 s of laser irradiation. The time-evolution is also measured upon addition of physiologically relevant concentrations of salts containing monovalent, divalent, or trivalent alkali ions. It is shown that some alkali ions can significantly inhibit strand breakages while some do not. The inhibition is due to electrostatic shielding of DNA, but significantly, the extent of such shielding is seen to depend on how each alkali ion binds to DNA. Results of experiments on strand breakages induced by thermalized particles produced upon plasma-induced photolysis of water, and their inhibition, suggest implications beyond studies of DNA; they open new vistas for utilizing simple nanosecond lasers to explore the effect of ultralow energy radiation on living matter under physiologically relevant conditions.
利用低能量激光脉冲（持续时间为 6ns，波长为 1064nm）在质粒 DNA（pUC19）的水溶液悬浮液中产生等离子体，从而生成电子和 OH 自由基。这些粒子在热化后，会导致 DNA 发生单链和双链断裂，同时可能导致碱基氧化/碱基降解。测量了随后结构修饰的时间演变；在激光辐照 30s 内即可观察到 DNA 损伤。在添加含有单价、二价或三价碱金属离子的生理相关浓度盐后，也测量了时间演变。结果表明，一些碱金属离子可以显著抑制链断裂，而有些则不能。这种抑制是由于 DNA 的静电屏蔽，但重要的是，这种屏蔽的程度取决于每个碱金属离子与 DNA 的结合方式。等离子体诱导光解水产生的热化粒子诱导的链断裂及其抑制的实验结果表明，其意义超出了 DNA 研究的范畴；它们为利用简单的纳秒激光在生理相关条件下探索超低能辐射对生命物质的影响开辟了新的前景。
