title: Monitoring one-electron photo-oxidation of guanine in DNA crystals using ultrafast infrared spectroscopy.
abstract: To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridyl-DNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium.
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.|Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: James P
authors.initials: JP
authors.lastname: Hall
authors.affiliation: School of Chemistry, Trinity College, University of Dublin, Dublin 2, Ireland.|Trinity Biomedical Science Institute (TBSI), Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Fergus E
authors.initials: FE
authors.lastname: Poynton
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.|School of Chemistry, Trinity College, University of Dublin, Dublin 2, Ireland.
authors.forename: Páraic M
authors.initials: PM
authors.lastname: Keane
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.|Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Gurung
authors.affiliation: Department of Pharmacy, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: John A
authors.initials: JA
authors.lastname: Brazier
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cardin
authors.affiliation: Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: Graeme
authors.initials: G
authors.lastname: Winter
authors.affiliation: School of Chemistry, Trinity College, University of Dublin, Dublin 2, Ireland.|Trinity Biomedical Science Institute (TBSI), Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Thorfinnur
authors.initials: T
authors.lastname: Gunnlaugsson
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Science &Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Sazanovich
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Science &Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: Christine J
authors.identifier: http://orcid.org/0000-0002-2556-9995
authors.initials: CJ
authors.lastname: Cardin
authors.affiliation: School of Chemistry, Trinity College, University of Dublin, Dublin 2, Ireland.
authors.forename: John M
authors.initials: JM
authors.lastname: Kelly
authors.affiliation: School of Chemistry, University College Dublin, Dublin 4, Ireland.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Quinn
mesh_terms: D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D004583:Electrons; D006147:Guanine / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013055:Spectrophotometry, Infrared
chemical_list: D006147:Guanine; D004247:DNA