title: DNA damage by OH radicals produced using intense, ultrashort, long wavelength laser pulses.
abstract: We probe femtosecond laser induced damage to aqueous DNA, relying on strong-field interaction with water wherein electrons and free radicals are generated in situ; these, in turn, interact with DNA plasmids under physiological conditions, producing nicks. Exposure to intense femtosecond pulses of 1350 and 2200 nm light induces single strand breaks and double strand breaks (DSBs) in DNA. At the longer wavelength (and at higher intensities), rotationally hot OH radicals induce DSBs, producing linear DNA. Strand breaks occur due to single or multiple OH hits on DNA. With 2200 nm light, DSBs are formed mostly by the action of two OH radicals; use of OH scavengers establishes that the probability of a two-hit event reduces much faster than a one-hit event as scavenger concentration is increased. Thermal effects do not induce DSBs with 2200 nm light.
authors.affiliation: Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Dharmadhikari
authors.affiliation: UM-DAE Centre for Excellence in Basic Science, Kalina Campus, Santa Cruz (East), Mumbai 400 098, India.
authors.forename: H
authors.initials: H
authors.lastname: Bharambe
authors.affiliation: Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104, India.
authors.forename: J A
authors.initials: JA
authors.lastname: Dharmadhikari
authors.affiliation: UM-DAE Centre for Excellence in Basic Science, Kalina Campus, Santa Cruz (East), Mumbai 400 098, India.
authors.forename: J S
authors.initials: JS
authors.lastname: D'Souza
authors.affiliation: Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005, India and Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104, India.
authors.forename: D
authors.initials: D
authors.lastname: Mathur
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D053903:DNA Breaks, Double-Stranded; D053904:DNA Breaks, Single-Stranded; D017665:Hydroxyl Radical / Q000737:chemistry*; D007834:Lasers; D013816:Thermodynamics
chemical_list: D017665:Hydroxyl Radical; D004247:DNA