Photooxidation of guanine by a ruthenium dipyridophenazine complex intercalated in a double-stranded polynucleotide monitored directly by picosecond visible and infrared transient absorption spectroscopy

Elias, Benjamin;Creely, Caitriona;Doorley, Gerard W.;Feeney, Martin M.;Kelly, John M.;et.al.
(2008) Chemistry: A European Journal — Vol. 14, n° 1, p. 369-375 (2008)

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Authors
  • Elias, BenjaminUniversité Libre de Bruxelles (ULB)
    Author
  • Creely, CaitrionaUniversity of Dublin, Trinity College (Ireland)
    Author
  • Doorley, Gerard W.University of Dublin, Trinity College (Ireland)
    Author
  • Feeney, Martin M.University of Dublin, Trinity College (Ireland)
    Author
  • Kelly, John M.University of Dublin, Trinity College (Ireland)
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Abstract
Transient species formed by photoexcitation (400 nm) of [Ru(dppz)(tap)(2)](2+) (1) (dppz = dipyrido[3,2-a:2',3'-c]phenazine; tap = 1,4,5,8-tetraazaphenanthrene) in aqueous solution and when intercalated into a double-stranded synthetic polynucleotide, [poly(dG-dC)](2), have been observed on a picosecond timescale by both visible transient absorption (allowing monitoring of the metal complex intermediates) and transient infrared (IR) absorption spectroscopy (allowing direct study of the DNA nucleobases). By contrast with its behavior when free in aqueous solution, excitation of 1 when bound to [poly(dGdC), causes a strong increase in absorbance at 515 nm due to formation of the reduced complex [Ru(dppz)(tap)(2)](+) (rate constant = (2.0 +/- 0.2) x 10(9) s(-1)). The subsequent reformation of 1 proceeds with a rate constant of (1.1 +/- 0.2) x 10(8) s(-1). When the process is carried out in D2O, the rates of forma-tion and removal of [Ru(dppz)(tap)(2)](+) are reduced (rate constants (1.5 +/- 0.3) x 10(9) and (0.7 +/- 0.2) x 10(8) s(-1) respectively) consistent with proton-coupled electron transfer processes. Picosecond transient IR measurements in the 1540-1720 cm(-1) region in D2O solution confirm that the reduction of 1 intercalated into [poly(dG-dC)](2) is accompanied by bleaching of IR ground-state bands of guanine (1690 cm(-1)) and cytosine (1656 cm(-1)), each with similar rate constants.
Affiliations
  • Université Libre de Bruxelles (ULB)Chimie Organique et Photochimie
  • University of Dublin, Trinity College (Ireland)Chemistry and Physics
  • University of Nottingham (U.K.)Chemistry
  • Rutherford Appleton Laboratory (Didcot - U.K.)Central Laser Facility

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Elias, B., Creely, C., Doorley, G. W., Feeney, M. M., Moucheron, C., Kirsch-DeMesmaeker, A., Dyer, J., Grills, D. C., George, M. W., Matousek, P., Parker, A. W., Towrie, M., & Kelly, J. M. (2008). Photooxidation of guanine by a ruthenium dipyridophenazine complex intercalated in a double-stranded polynucleotide monitored directly by picosecond visible and infrared transient absorption spectroscopy. Chemistry: A European Journal, 14(1), 369-375. https://doi.org/10.1002/chem.200700564 (Original work published 2008)