title: Formation of plasmid DNA strand breaks induced by low-energy ion beam: indication of nuclear stopping effects.
abstract: Plasmid pGEM 3zf(+) was irradiated by nitrogen ion beam with energies between 20 and 100 keV and the fluence kept as 1x10(12)ions/cm2. The irradiated plasmid was assayed by neutral electrophoresis and quantified by densitometry. The yields of DNA with single-strand and double-strand breaks first increased then decreased with increasing ion energy. There was a maximal yield value in the range of 20-100 keV. The relationship between DNA double-strand breaks (DSB) cross-section and linear energy transfer (LET) also showed a peak-shaped distribution. To understand the physical process during DNA strand breaks, a Monte Carlo calculation code known as TRIM (Transport of Ions in Matter) was used to simulate energy losses due to nuclear stopping and to electronic stopping. It can be assumed that nuclear stopping plays a more important role in DNA strand breaks than electronic stopping in this energy range. The physical mechanisms of DNA strand breaks induced by a low-energy ion beam are also discussed.
authors.affiliation: Ion Beam Laboratory, Shanghai Institute of Metallurgy, Chinese Academy of Sciences.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: B
authors.initials: B
authors.lastname: Jiang
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: X
authors.initials: X
authors.lastname: Ding
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.forename: G
authors.initials: G
authors.lastname: Yin
mesh_terms: D004249:DNA Damage / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D004277:DNA, Single-Stranded / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects; D019471:Elementary Particle Interactions; D004926:Escherichia coli; D007477:Ions; D018499:Linear Energy Transfer; D008962:Models, Theoretical; D009010:Monte Carlo Method; D009584:Nitrogen / Q000009:adverse effects; D010957:Plasmids / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D007477:Ions; D009584:Nitrogen