Induction of strand breaks in DNA films by low energy electrons and soft X-ray under nitrous oxide atmosphere

Abstract

Five-monolayer (5ML) plasmid DNA films deposited on glass and tantalum substrates were exposed to Al K α X-rays of 1.5 keV under gaseous nitrous oxide (N 2 O) at atmospheric pressure and temperature. Whereas the damage yields for DNA deposited on glass are due to soft X-rays, those arising from DNA on tantalum are due to both the interaction of low energy photoelectrons from the metal and X-rays. Then, the differences in the yields of damage on glass and tantalum substrates, essentially arises from interaction of essentially low-energy electrons (LEEs) with DNA molecules and the surrounding atmosphere. The G-values (i.e., the number of moles of product per Joule of energy absorbed) for DNA strand breaks induced by LEEs (G LEE ) and the lower limit of G-values for soft X-ray photons (G XL ) were calculated and the results compared to those from previous studies under atmospheric conditions and other ambient gases, such as N 2 and O 2 . Under N 2 O, the G-values for loss of supercoiled DNA are 103±15 nmol/J for X-rays, and 737±110 nmol/J for LEEs. Compared to corresponding values in an O 2 atmosphere, the effectiveness of X-rays to damage DNA in N 2 O is less, but the G value for LEEs in N 2 O is more than twice the corresponding value for an oxygenated environment. This result indicates a higher effectiveness for LEEs relative to N 2 and O 2 environments in causing SSB and DSB in an N 2 O environment. Thus, the previously observed radiosensitization of cells by N 2 O may not be only due to OH • radicals but also to the reaction of LEE with N 2 O molecules near DNA. The previous experiments with N 2 and O 2 and the present one demonstrate the possibility to investigate damage induced by LEEs to biomolecules under various type of surrounding atmospheres.

Recent Advances in Plasma-Based Cancer Treatments: Approaching Clinical Translation through an Intracellular View

“…Hydroxyl free radicals carry no charge, but have a strong affinity for electrons causing to remove hydrogen atoms from biomolecules. For instance, abstraction of deoxyribose hydrogen atoms from DNA initiates at least one pathway, which resulting in the production of a DNA strand scission [115][116][117][118]. Free radicals and electrons can also interact with other surrounding molecules like oxygen to generate the highly reactive secondary free radicals and ROS, particularly the superoxide anion radical (O 2…”

Dynamics of Dissociative Electron–Molecule Interactions in Condensed Methanol

“…The radiation chemistry of condensed methanol is also of astrochemical interest because methanol is found in relatively high abundance in protostar environments. Methanol is thought to be an important precursor in cosmic ices not only to species such as methyl formate (HCOOCH 3 ), ethylene glycol (HOCH 2 CH 2 OH), and dimethyl ether (CH 3 OCH 3 ) but also to many prebiotic species such as simple sugars and amino acids. − Because of such applications, the high-energy radiolysis of methanol has been extensively studied over a period spanning seven decades. − More recent advances, however, have demonstrated that studying the interactions of low-energy electrons with condensed matter is essential to obtaining a fundamental understanding of radiation chemistry because the interactions of high-energy radiation, such as cosmic rays ( E max ∼ 10 20 eV), with matter produce large numbers of low-energy (<15 eV) secondary electrons, which are thought to initiate radiolysis reactions in the condensed phase. , In this publication, we investigate the chemistry induced in condensed methanol by such low-energy electrons and explore the role of dissociative electron attachment, a process in which an electron is temporarily captured by a molecular target to form a temporary negative ion that subsequently dissociates into anionic and neutral fragments, in the condensed-phase radiolysis of methanol.…”

“…5−9 More recent advances, however, have demonstrated that studying the interactions of low-energy electrons with condensed matter is essential to obtaining a fundamental understanding of radiation chemistry because the interactions of high-energy radiation, such as cosmic rays (E max ∼ 10 20 eV), with matter produce large numbers of low-energy (<15 eV) secondary electrons, which are thought to initiate radiolysis reactions in the condensed phase. 10,11 In this publication, we investigate the chemistry induced in condensed methanol by such low-energy electrons and explore the role of dissociative electron attachment, a process in which an electron is temporarily captured by a molecular target to form a temporary negative ion that subsequently dissociates into anionic and neutral fragments, in the condensed-phase radiolysis of methanol.Cross sections for electron collisions with gaseous methanol have been studied experimentally from the 1930s until the present day. 12−15 Early experiments on the electron-induced dissociation of gaseous methanol at low electron energies demonstrated the formation of several anions such as H − , OH − , O − , and CH 3 O − .…”

Applying Petri nets to modeling the chemical stage of radiobiological mechanism

“…It may be helpful in studying the damage effect of individual radicals to DNA molecules and, consequently, also for the study of the radiobiological effect on various living cells (see e.g. [1,2]). In the presented paper we have assumed the spherical symmetry of the corresponding radical clusters.…”