Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions.

TLDR: It is shown that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions and the differences in damage yields recorded with the gold and glass substrates is essentially attributed to the interaction of low- energy electrons with DNA under vacuum and hydrated conditions.

Abstract: In this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively.

Figures

Figure 1. Schematic overview of the type of apparatus used to irradiate samples with 1.5 keV Al KR X-ray photons under atmospheric conditions: (A) baratron, (B) adjustable leak valve, (C) concave aluminum cathod, (D) high voltage electric feedthrough, (E) aluminum foil, (F) atmosphere, (G) glass-ceramic support, (H) quartz tube.

Figure 4. Energy spectrum of induced secondary electron emission from a gold surface.

TABLE 1: Percentage Yield per 1012 photons · cm-2 for the Loss of Supercoiled DNA in 5 ML Films Deposited on Glass and Gold Substrates and Held under Vacuum or Atmospheric Conditionsa

Figure 3. X-ray exposure curves for the loss of the supercoiled DNA under atmospheric conditions on glass and gold substrates. The points represent the means of three independent experiments and the error bars represent standard deviation of the means.

Figure 2. X-ray exposure curves for the loss of the supercoiled DNA in vacuum on glass and gold substrates. The points represent the means of three independent experiments and the error bars represent standard deviation of the means.

Frequently asked questions

Q1. What are the contributions in "Damage induced to dna by low-energy (0-30 ev) electrons under vacuum and atmospheric conditions" ?

Brun et al. this paper showed that photoelectrons emitted from a gold substrate can be used as a source of low-energy electrons ( LEEs ) to irradiate DNA films under atmospheric conditions.