On the capturing of low-energy electrons by DNA.

Many of the mutagenic or lethal effects of ionization radiation can be attributed to damage caused to the DNA by low-energy electrons. To gain insight on the parameters affecting this process, we measured the low-energy electron (<2 eV) transmission yield through self-assembled monolayers of short DNA oligomers. The electrons that are not transmitted are captured by the layer. Hence, the transmission reflects the capturing efficiency of the electrons by the layer. The dependence of the capturing probability on the base sequence was studied, as was the state of the captured electrons. It is found that the capturing probability scales with the number of G bases in the single-stranded oligomers and depends on their clustering level. Using two-photon photoelectron spectroscopy, we find that, once captured, the electrons do not reside on the bases. Rather, the state of the captured electrons is insensitive to the sequence of the oligomer. Double-stranded DNA does not capture electrons as efficiently as single-stranded oligomers; however, once captured, the electrons are bound more strongly than to the single strands.

[1]  D. Hunting,et al.  Cross Sections for Low-Energy (10 – 50 eV) Electron Damage to DNA , 2002, Radiation research.

[2]  C. Harris,et al.  Electron Solvation in Two Dimensions , 2002, Science.

[3]  J A Aguilera,et al.  Polyamine-induced compaction and aggregation of DNA--a major factor in radioprotection of chromatin under physiological conditions. , 1996, Radiation research.

[4]  Antoine Moreau,et al.  Cluster size effects upon anion solvation of N-heterocyclic molecules and nucleic acid bases , 2000 .

[5]  S. Srivastava,et al.  Excited state dipole moments and geometries of the bases of nucleic acids , 1980 .

[6]  G. Gallup,et al.  ELECTRON ATTACHMENT ENERGIES OF THE DNA BASES , 1998 .

[7]  E. Chen,et al.  The negative ion states of molecules: adenine and guanine. , 2001, Biochemical and biophysical research communications.

[8]  N. Hush,et al.  Ionization potentials and donor properties of nucleic acid bases and related compounds , 1975 .

[9]  M. Sevilla,et al.  Radiation-induced DNA damage as a function of hydration. I. Release of unaltered bases. , 1992, Radiation research.

[10]  J. R. Williamson,et al.  G-quartet structures in telomeric DNA. , 1994, Annual review of biophysics and biomolecular structure.

[11]  J. V. Ortiz,et al.  Diffuse-Bound and Valence-Bound Anions of Cytosine , 2001 .

[12]  S. Daube,et al.  Controlling the Adsorption and Reactivity of DNA on Gold , 2003 .

[13]  N. Rösch,et al.  Energetics of excess electron transfer in DNA , 2001 .

[14]  M. Charlier,et al.  Radioprotection of DNA by polyamines. , 1995, International journal of radiation biology.

[15]  L. Chin,et al.  Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation , 2000, Nature Genetics.

[16]  H. Abdoul-Carime,et al.  Fragmentation of short single DNA strands by 1-30 eV electrons: dependence on base identity and sequence , 2002, International journal of radiation biology.

[17]  J. Ward,et al.  Redox equilibrium between guanyl radicals and thiocyanate influences base damage yields in gamma irradiated plasmid DNA. Estimation of the reduction potential of guanyl radicals in plasmid DNA in aqueous solution at physiological ionic strength , 2001, International journal of radiation biology.

[18]  E. Chen,et al.  The determination of absolute electron affinities of the purines and pyrimidines in DNA and RNA from reversible reduction potentials. , 1991, Biochemical and biophysical research communications.

[19]  Pierre Cloutier,et al.  DNA strand breaks induced by 0-4 eV electrons: the role of shape resonances. , 2004, Physical review letters.

[20]  T. Fauster,et al.  Time-resolved coherent photoelectron spectroscopy of quantized electronic states on metal surfaces , 1997 .

[21]  M. Tarlov,et al.  Quantitative analysis and characterization of DNA immobilized on gold. , 2003, Journal of the American Chemical Society.

[22]  M. Ratner,et al.  Charge hopping in DNA. , 2001, Journal of the American Chemical Society.

[23]  Piotr Skurski,et al.  Damage to model DNA fragments from very low-energy (<1 eV) electrons. , 2004, Journal of the American Chemical Society.

[24]  Bernd Giese,et al.  Direct observation of hole transfer through DNA by hopping between adenine bases and by tunnelling , 2001, Nature.

[25]  E. Shimoni,et al.  Stress, order and survival , 2002, Nature Reviews Molecular Cell Biology.