Journal of Radiation Protection and Research

The Korean Association for Radiation Protection (대한방사선방어학회)
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DNA Damage by X-ray and Low Energy Electron Beam Irradiation

X선과 저에너지 전자선에 의한 DNA 손상

  • 박연수 (충남대학교 물리학과) ;
  • 노형아 (충남대학교 물리학과) ;
  • 조혁 (충남대학교 물리학과) ;
  • ;
  • ;
  • ;
  • Published : 2008.06.30
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Abstract

We observed DNA damages as a function of mean absorbed dose to identify the indirect effect of high-energy radiation such as x-ray. Monolayer films of lyophilized pGEM-3Zf(-) plasmid DNA deposited on tantalum foils were exposed to Al $K{\alpha}$ X-ray (1.5 keV) for 0, 3, 7 and 10 min, respectively, in a condition of ultrahigh vacuum state. We compared DNA damages by X-ray irradiation with those by 3 eV electron irradiation. X-ray photons produced low-energy electrons (mainly below 20 eV) from the tantalum foils and DNA damage was induced chiefly by these electrons. For electron beam irradiation, DNA damage was directly caused by 3 eV electrons. Irradiated DNA was analyzed by agarose gel electrophoresis and quantified by ImagaQuant program. The quantities of remained supercoiled DNA after irradiation were linearly decreased as a function of mean absorbed dose. On the other hand, the yields of nicked circular (single strand break, SSB) and interduplex crosslinked form 1 DNA were linearly increased as a function of mean absorbed dose. From this study, it was confirmed that DNA damage was also induced by low energy electrons ($0{\sim}10\;eV$) even below threshold energies for the ionization of DNA.

X선과 같은 고에너지 방사선에 의한 DNA 손상 중 간접적인 손상을 확인하기 위하여 탄탈륨(Ta) 박막위에 동결건조 과정으로 만들어진 pGEM-3Zf(-) plasmid DNA 단일층(monolayer)의 박막을 만든 다음, 에너지가 1.5 keV인 Al $K{\alpha}$ X선을 0분, 3분, 7분, 10분 동안 초고진공 상태에서 이 DNA 단일층에 조사하여 평균 흡수선량(mean absorbed dose)의 변화에 따른 DNA 손상을 관찰하였다. 또한 3 eV의 낮은 에너지 전자선을 조사하여 그 결과를 X선을 조사한 경우와 비교하였다. X선과 낮은 에너지 전자선으로 조사된 plasmid DNA를 전기영동(electrophoresis) 방법을 이용해 supercoiled DNA와 unsupercoiled DNA로 분리한 후 각각을 정량적으로 분석하였다. Supercoiled DNA는 X선과 3 eV 전자선의 조사에 따른 평균흡수선량이 증가함에 따라 선형적으로 감소했다. 그와 반대로 circular DNA와 crosslinked form 1 DNA는 평균흡수선량이 증가함에 따라 선형적으로 증가했다. 이것은 supercoiled DNA가 낮은 에너지 전자와 상호작용하여 외가닥 절단(single strand break)을 일으켰고 그 결과 unsupercoiled DNA로 변화되었음을 보여준다. 본 실험을 통해 X선과 같은 고에너지 방사선에 의한 DNA의 간접적 손상이 일어남을 관찰할 수 있었고, DNA의 이온화 에너지보다 작은 에너지($0{\sim}10\;eV$)를 갖는 전자에 의해서도 DNA 손상이 일어날 수 있음을 확인할 수 있었다.

Keywords

References

  1. Ptasinska S, Sanche L. On the mechanism of anion desorption from DNA induced by low energy electrons. J. Chem. Phys. 2006;125:144713 https://doi.org/10.1063/1.2338320
  2. Barrios R, Skurski P, Simons J. Mechanism for Damage to DNA by low-energy electrons. J. Phys. Chem. B 2002; 106:7991-7994 https://doi.org/10.1021/jp013861i
  3. Boudaiffa B, Cloutier P, Hunting D, Huels MA, Sanche L. Resonant formation of DNA strand breaks by low-energy (3-20 eV) electrons. Science 2000;287:1658-1660 https://doi.org/10.1126/science.287.5458.1658
  4. Ptasinska S, Denifl S, Scheier P, Mark TD. Inelastic electron interaction (attachment/ionization) with deoxyribose. J. Chem. Phys. 2004;120(18):8505-8511 https://doi.org/10.1063/1.1690231
  5. Park YS, Cho H, Parenteau L, Bass AD, Sanche L. Cross sections for electron trapping by DNA and its component subunits1: Condensed tetrahydrofuran deposited on Kr. J. Chem. Phys. 2006;125:074714 https://doi.org/10.1063/1.2229201
  6. Simons J. How do low-energy(0.1-2 eV) electrons cause DNA-strand breaks? Acc. Chem. Res. 2006;39:772-779 https://doi.org/10.1021/ar0680769
  7. Rowntree P, Parenteau L, Sanche L. Electron Stimulated Desorption via dissociative attachment in amorphous H$_2$O. J. Chem. Phys. 1991;94(12):8570-8576 https://doi.org/10.1063/1.460090
  8. Levesque PL, Michaud M, Cho WS, Sanche L. Absolute electronic excitation cross sections for low-energy electron (5-12 eV) scattering from condensed thymine. J. Chem. Phys. 2005;122:224704 https://doi.org/10.1063/1.1925610
  9. Levesque PL, Michaud M, Sanche L. Absolute vibrational and electronic cross sections for low-energy electron(2-12 eV) scattering from condensed pyrimidine. J. Chem. Phys. 2004;122:094701 https://doi.org/10.1063/1.1854121
  10. Lepage M, Letarte S, Michaud M, Motte-Tollet F, Hubin- Franskin MJ, Roy D, Sanche L. Electron spectroscopy of resonance-enhanced vibrational excitations of gaseous and solid tetrahydrofuran. J. Chem. Phys. 1998;109:5980-5986 https://doi.org/10.1063/1.477223
  11. Bass AD, Sanche L. Dissociative electron attachment and charge transfer in condensed matter. Rad. Phys. Chem. 2003;68:3-13 https://doi.org/10.1016/S0969-806X(03)00244-5
  12. Pan X, Cloutier P, Hunting D, Sanche L. Dissociative electron attachment to DNA. Phys. Rev. Lett. 2003;90(20):208102 https://doi.org/10.1103/PhysRevLett.90.208102
  13. Martin F, Burrow PD, Cai Z, Cloutier P, Hunting D, Sanche L. DNA strand breaks induced by 0-4 eV electrons: The role of shape resonances. Phys. Rev. Lett. 2004;93(6):068101 https://doi.org/10.1103/PhysRevLett.93.068101
  14. Cai Z, Cloutier P, Hunting D, Sanche L. Enhanced DNA damage induced by secondary electron emission from a tantalum surface exposed to soft X-rays. Rad. Res. 2006; 165:365-371 https://doi.org/10.1667/RR3509.1
  15. Denifl S, Ptasinska S, Hanel G, Gstir B, Probst M, Scheier P, Mark TD. Electron attachment to gas-phase uracil. J. Chem. Phys. 2004;120(14):6557-6565 https://doi.org/10.1063/1.1649724
  16. Denifl S, Ptasinska S, Probst M, Hrusak J, Scheier P, Mark TD. Electron attachment to the gas-phase DNA bases Cytosine and Thymine. J. Phys. Chem. A 2004;108:6562-6569 https://doi.org/10.1021/jp049394x
  17. Cai Z, Cloutier P, Hunting D, Sanche L. Comparison between X-ray photon and secondary electron damage to DNA in vacuum. J. Phys. Chem. B 2005 ;109:4796-4800 https://doi.org/10.1021/jp0459458
  18. Panajotovic R, Martin F, Cloutier P, Hunting D, Sanche L. Effective cross sections for production of single-strand breaks in plasmid DNA by 0.1 to 4.7 eV electrons. Rad. Res. 2006; 165:452-459 https://doi.org/10.1667/RR3521.1
  19. Huels MA, Boudaiffa B, Cloutier P, Hunting D, Sanche L. Single, Double, and Multiple Double Strand Breaks Induced in DNA by 3-100 eV Electrons. J. Am. Chem. Soc. 2003; 125:4467-4477 https://doi.org/10.1021/ja029527x
  20. Boudaiffa B, Cloutier P, Hunting D, Huels MA, Sanche L. Cross sections for Low-Energy (10-50 eV) Electron Damage to DNA. Rad. Res. 2002;157:227-234 https://doi.org/10.1667/0033-7587(2002)157[0227:CSFLEE]2.0.CO;2