Effective cross sections for production of single-strand breaks in plasmid DNA by 0.1 to 4.7 eV electrons.

Effective cross sections for production of single-strand breaks in plasmid DNA by 0.1 to 4.7 eV electrons.

Radiation research (2006-04-04)

Radmila Panajotovic, Frédéric Martin, Pierre Cloutier, Darel Hunting, Léon Sanche

ABSTRACT

We determined effective cross sections for production of single-strand breaks (SSBs) in plasmid DNA [pGEM 3Zf(-)] by electrons of 10 eV and energies between 0.1 and 4.7 eV. After purification and lyophilization on a chemically clean tantalum foil, dry plasmid DNA samples were transferred into a high-vacuum chamber and bombarded by a monoenergetic electron beam. The amount of the circular relaxed DNA in the samples was separated from undamaged molecules and quantified using agarose gel electrophoresis. The effective cross sections were derived from the slope of the yield as a function of exposure and had values in the range of 10(-15)- 10(-14) cm2, giving an effective cross section of the order of 10(-18) cm2 per nucleotide. Their strong variation with incident electron energy and the resonant enhancement at 1 eV suggest that considerable damage is inflicted by very low-energy electrons to DNA, and it indicates the important role of pi* shape resonances in the bond-breaking process. Furthermore, the fact that the energy threshold for SSB production is practically zero implies that the sensitivity of DNA to electron impact is universal and is not limited to any particular energy range.

MATERIALS

Product Number

Brand

Product Description

GF99542368

Tantalum, foil, 10mm disks, thickness 0.03mm, as rolled, 99.9%

GF97180870

Tantalum, foil, light tested, 50x50mm, thickness 0.01mm, 99.9%

GF16472448

Tantalum, foil, 4mm disks, thickness 0.25mm, annealed, 99.9%

GF91998253

Tantalum, foil, light tested, 100x100mm, thickness 0.025mm, as rolled, 99.9%

GF11923589

Tantalum, foil, light tested, 25x25mm, thickness 0.006mm, 99.9%

GF52742099

Tantalum, foil, light tested, 100x100mm, thickness 0.034mm, as rolled, 99.9%

GF93289090

Tantalum, foil, light tested, 25x25mm, thickness 0.004mm, 99.9%

GF98156144

Tantalum, foil, not light tested, 25x25mm, thickness 0.0015mm, 99.9%

GF42889517

Tantalum, foil, light tested, 150x300mm, thickness 0.075mm, annealed, 99.9%

GF15979494

Tantalum, foil, light tested, 50x50mm, thickness 0.075mm, annealed, 99.9%

GF19254472

Tantalum, foil, not light tested, 25x25mm, thickness 0.0005mm, 99.9%

GF65369324

Tantalum, foil, light tested, 100x100mm, thickness 0.05mm, annealed, 99.9%

GF00815958

Tantalum, foil, not light tested, 25x25mm, thickness 0.001mm, 99.9%

GF90076989

Tantalum, foil, not light tested, 50x50mm, thickness 0.0015mm, 99.9%

GF63410048

Tantalum, foil, light tested, 50x50mm, thickness 0.0075mm, 99.9%

GF84327510

Tantalum, foil, not light tested, 25x25mm, thickness 0.01mm, 99.9%

GF89056648

Tantalum, foil, not light tested, 100x100mm, thickness 0.003mm, 99.9%

GF15129817

Tantalum, foil, not light tested, 50x50mm, thickness 0.01mm, 99.9%

GF48352798

Tantalum, foil, light tested, 50x50mm, thickness 0.006mm, 99.9%

GF98666230

Tantalum, foil, light tested, 150x150mm, thickness 0.03mm, as rolled, 99.9%

GF66499891

Tantalum, foil, 6mm disks, thickness 0.02mm, 99.9%

GF23883576

Tantalum, foil, 1m coil, thickness 0.1mm, coil width .62mm, as rolled, 99.9%

GF55289548

Tantalum, foil, 15mm disks, thickness 0.5mm, annealed, 99.9%

GF62916318

Tantalum, foil, 10mm disks, thickness 0.75mm, annealed, 99.9%

GF81952410

Tantalum, foil, 8mm disks, thickness 0.25mm, annealed, 99.9%

GF21331998

Tantalum, foil, 4mm disks, thickness 0.02mm, 99.9%

GF84918381

Tantalum, foil, 50mm disks, thickness 0.034mm, as rolled, 99.9%

GF38844355

Tantalum, foil, 15mm disks, thickness 0.015mm, 99.9%

GF53856186

Tantalum, foil, 1m coil, thickness 0.03mm, coil width 1.2mm, annealed, 99.9%

GF99539667

Tantalum, foil, 2m coil, thickness 0.025mm, coil width 0.75mm, annealed, 99.9%