title: Infrared characterization of the guanine radical cation: finger printing DNA damage.
abstract: Oxidation of DNA represents a major pathway of genetic mutation. We have applied infrared spectroscopy in 77 K glass with supporting density functional theory (DFT) calculations (EDF1/6-31+G*) to provide an IR signature of the guanine radical cation G(+*), formed as a result of 193 nm photoionization of DNA. Deprotonation of this species to produce the neutral radical G(-H)(*) does not occur in 77 K glass. DFT calculations indicate that the formation of G(+*) within the double helix does not significantly perturb the geometry of the G/C pair, even though there is a significant movement of the N(1) proton away from G toward C. However, this is in stark contrast to drastic changes that are expected if full deprotonation of G/C occurs, producing the G(-H)(*)/C pair. These results are discussed in light of solution-phase time-resolved IR spectroscopic studies and demonstrate the power of IR to follow dynamics of DNA damage in natural environments.
authors.affiliation: Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK. a.w.parker@stfc.ac.uk
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Parker
authors.forename: Ching Yeh
authors.initials: CY
authors.lastname: Lin
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
authors.forename: Marina K
authors.initials: MK
authors.lastname: Kuimova
mesh_terms: D002412:Cations / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D004249:DNA Damage; D006147:Guanine / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D013055:Spectrophotometry, Infrared
chemical_list: D002412:Cations; D006147:Guanine; D004247:DNA