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Electron transfer between metal complexes bound to DNA: variations in sequence, donor, and metal binding mode

Stemp, Eric D. A. and Holmlin, R. Erik and Barton, Jacqueline K. (2000) Electron transfer between metal complexes bound to DNA: variations in sequence, donor, and metal binding mode. Inorganica Chimica Acta, 297 (1-2). pp. 88-97. ISSN 0020-1693. doi:10.1016/S0020-1693(99)00289-3.

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Using luminescence spectroscopy and single photon counting, photoinduced electron transfer (ET) reactions between photoexcited [M(phen)_2dppz ^(2+) (phen = 1,10-phenanthroline, dppz=dipyridophenazine, M=Ru or Os) and the electron acceptors Rh(phi)_2bpy^(3+) (phi=9,10-phenanthrenequinone diimine, bpy=2,2′-bipyridine) and Ru(NH_3)_6^(3+) were studied as a function of DNA sequence in long DNA polymers. In addition, the thermal back reactions between M(III) and reduced acceptor were also followed by transient absorption spectroscopy. The comparison of ET reactions of the isostructural donors Os and Ru with an intercalated acceptor, Rh(phi)_2bpy^(3+), and an externally bound acceptor, Ru(NH_3)_6^(3+), helps to elucidate which factors are important for electron transfer between DNA-bound intercalators. Ru(phen)_2dppz^(2+) and Os(phen)_2dppz^(2+) show nearly identical quenching by Rh(phi)_2bpy^(3+) for a given DNA polymer, with an efficient quenching process that occurs on a time scale much faster than the excited state lifetime. We find that Rh(phi)_2bpy^(3+) and Ru(NH_3)_6^(3+) show opposite trends for quenching of DNA-bound M(phen)_2dppz^(2+). Quenching by intercalated Rh(phi)_2bpy^(3+) is most efficient in AT-only DNA polymers and less efficient in GC-only polymers, whereas for groove-bound Ru(NH_3)_6^(3+), the reverse is observed. The intrinsic excited state lifetime of Ru(phen)_2dppz^(2+) bound to DNA and the luminescence quenching efficiency by Ru(NH_3)_6^(3+) provide indicators of the solvent accessibility of the DNA-bound dppz donor. On this basis, we attribute the difference in ET reactivity among the various DNA polymers to differences in how well M(phen)_2dppz^(2+) stacks in DNA.

Item Type:Article
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URLURL TypeDescription
Stemp, Eric D. A.0000-0003-2098-4214
Barton, Jacqueline K.0000-0001-9883-1600
Additional Information:© 2000 Elsevier Science S.A. Received 9 March 1999; accepted 9 June 1999. Available online 24 January 2000. We thank the NIH (GM 49216) for financial support of this research, the Ralph M. Parsons foundation for a predoctoral fellowship (R.E.H.), and Mount St. Mary’s College Professional Development Fund for additional support (E.D.A.S.). We also thank Michelle Arkin for helpful discussions and Steve Lippard for first inspiring one of us (J.K.B.) to explore the many fascinating interactions of metal complexes with DNA.
Funding AgencyGrant Number
NIHGM 49216
Ralph M. Parsons FoundationUNSPECIFIED
Mount St. Mary’s CollegeUNSPECIFIED
Subject Keywords:Electron transfer; Metal complexes; DNA complexes
Issue or Number:1-2
Record Number:CaltechAUTHORS:20160323-092524330
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Official Citation:Eric D.A Stemp, R. Erik Holmlin, Jacqueline K Barton, Electron transfer between metal complexes bound to DNA: variations in sequence, donor, and metal binding mode, Inorganica Chimica Acta, Volume 297, Issues 1–2, January 2000, Pages 88-97, ISSN 0020-1693, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65612
Deposited By: Ruth Sustaita
Deposited On:23 Mar 2016 20:34
Last Modified:10 Nov 2021 23:47

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