title: Relaxation, linearization and fragmentation of supercoiled circular DNA by tungsten microprojectiles.
abstract: The aim of the study was to characterize DNA lesions caused by microprojectile bombardment and by the post-bombardment presence of tungsten particles in transformed cells. For the sake of simplicity, plasmid DNA was used as a target for bombardment with naked tungsten particles. Unexpectedly extensive DNA degradation was observed under standard bombardment conditions. However, no further DNA fragmentation occurred under post-bombardment conditions, simulated by incubation of plasmid DNA with a suspension of tungsten particles. Instead, relaxation and linearization of supercoiled circular plasmids (pAHC25 and others) took place. It is concluded that the observed linearization (a single site double-strand break in DNA circle) results from the ability of tungsten to catalyse the hydrolysis of phosphodiester bonds in torsionally strained sites of native DNA selectively.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland. krishna@ibb.waw.pl
authors.forename: C
authors.initials: C
authors.lastname: Krysiak
authors.forename: B
authors.initials: B
authors.lastname: Mazus
authors.forename: J
authors.initials: J
authors.lastname: Buchowicz
mesh_terms: D004249:DNA Damage; D053938:DNA Fragmentation; D004270:DNA, Circular / Q000737:chemistry*; D004278:DNA, Superhelical / Q000737:chemistry*; D009690:Nucleic Acid Conformation / Q000187:drug effects; D010957:Plasmids / Q000235:genetics; D014414:Tungsten / Q000633:toxicity*
chemical_list: D004270:DNA, Circular; D004278:DNA, Superhelical; D014414:Tungsten