Solution Photoreactivity of Phenanthrenequinone Diimine Complexes of Rhodium and Correlations with DNA Photocleavage and Photooxidation

Turró, Claudia; Hall, Daniel B.; Chen, Wei; Zuilhof, Han; Barton, Jacqueline K.; Turro, Nicholas J.

doi:10.1021/jp981013q

Cited by 33 publications

(28 citation statements)

References 29 publications

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“…The TA difference spectra of Rh-DNA and Re-DNA are similar to spectra observed upon photoexcitation of [Rh(phi) 2 (bpy)] 3+ in water 54,64 and [Re(CO) 3 (dppz)(py)] + in acetonitrile, 45 respectively. However, the TA spectra of the three conjugates also exhibit features in common with the reduced state spectra observed by spectroelectrochemistry.…”

Section: Discussionsupporting

confidence: 65%

Using Metal Complex Reduced States to Monitor the Oxidation of DNA

2011

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Metallointercalating photooxidants interact intimately with the base stack of double-stranded DNA and exhibit rich photophysical and electrochemical properties, making them ideal probes for the study of DNA-mediated charge transport (CT). The complexes [Rh(phi)2(bpy′)]3+ (phi = 9,10-phenanthrenequinone diimine; bpy′ = 4-methyl-4′-(butyric acid)-2,2′-bipyridine), [Ir(ppy)2(dppz′)]+ (ppy = 2-phenylpyridine; dppz′ = 6-(dipyrido[3,2-a:2′,3′-c]phenazin-11-yl)hex-5-ynoic acid), and [Re(CO)3(dppz)(py′)]+ (dppz = dipyrido[2,3-a:2′,3′-c]phenazine; py′ = 3-(pyridin-4-yl)-propanoic acid) were each covalently tethered to DNA in order to compare their photooxidation efficiencies. Biochemical studies show that upon irradiation, the three complexes oxidize guanine by long-range DNA-mediated CT with the efficiency: Rh > Re > Ir. Comparison of spectra obtained by spectroelectrochemistry after bulk reduction of the free metal complexes with those obtained by transient absorption (TA) spectroscopy of the conjugates suggests that the reduced metal states form following excitation of the conjugates at 355 nm. Electrochemical experiments and kinetic analysis of the TA decays indicate that the thermodynamic driving force for CT, variations in the efficiency of back electron transfer, and coupling to DNA are the primary factors responsible for the trend observed in the guanine oxidation yield of the three complexes.

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Section: Discussionsupporting

confidence: 65%

Using Metal Complex Reduced States to Monitor the Oxidation of DNA

2011

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“…Both have sufficient excited-state reduction potentials (2.0 and 1.9 V vs. NHE, respectively) (29,30) to oxidize each of the four natural DNA bases, and neither photoreduces DNA bases (31,32). Photoinduced electron transfer from r CP C to each of these oxidants is observed in solution.…”

Section: Resultsmentioning

confidence: 99%

Long-range oxidative damage to cytosines in duplex DNA

Shao

O’Neill²,

Barton³

2004

Proc. Natl. Acad. Sci. U.S.A.

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140

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Charge transport (CT) through DNA has been found to occur over long molecular distances in a reaction that is sensitive to intervening structure. The process has been described mechanistically as involving diffusive charge-hopping among low-energy guanine sites. Using a kinetically fast electron hole trap, N4-cyclopropylcytosine ( CP C), here we show that hole migration must involve also the higher-energy pyrimidine bases. In DNA assemblies containing either [Rh(phi)2(bpy )] 3؉ or an anthraquinone derivative, two highenergy photooxidants, appreciable oxidative damage at a distant CP C is observed. The damage yield is modulated by lower-energy guanine sites on the same or complementary strand. Significantly, the efficiency in trapping at CP C is equivalent to that at N2-cyclopropylguanosine ( CP G). Indeed, even when CP G and CP C are incorporated as neighboring bases on the same strand, their efficiency of photodecomposition is comparable. Thus, CT is not simply a function of the relative energies of the isolated bases but instead may require orbital mixing among the bases. We propose that charge migration through DNA involves occupation of all of the DNA bases with radical delocalization within transient structure-dependent domains. These delocalized domains may form and break up transiently, facilitating and limiting CT. This dynamic delocalized model for DNA CT accounts for the sensitivity of the process to sequence-dependent DNA structure and provides a basis to reconcile and exploit DNA CT chemistry and physics.charge transport ͉ delocalized domain ͉ radical trap ͉ base dynamics O xidative damage to DNA from a distance through longrange migration of charge has now been established in many DNA assemblies by using different pendant photooxidants through both biochemical and spectroscopic assays (1-8). The DNA base pair stack can mediate charge transport (CT) over at least 200 Å (2, 3), and the reaction is exquisitely sensitive to the dynamic structure and stacking within the DNA duplex (9, 10). This sensitivity to perturbations in base pair stacking has been advantageous in the development of DNA-based sensors for mutational analysis (11) and may provide a role for DNAmediated CT within the cell (12), but it has limited the application of physical techniques to explore CT mechanistically.Although not a robust molecular wire, the DNA duplex has in some experiments been characterized as a wide band gap semiconductor (13,14). More prevalent have been models of incoherent CT involving a mixture of localized charge-hopping among low-energy sites, guanines and sometimes adenines, and tunneling through higher-energy pyrimidine bases (15-18). These mechanisms do not provide a rationale, however, for the sensitivity of CT to DNA structure. We have observed that DNA CT is gated by the dynamical motions of the DNA bases (9, 19) and have described DNA CT as conformationally gated hopping through transient, well stacked DNA domains (20).Our experimental strategy to probe for hole density on pyrimidines exploits the rapid ...

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“…Excitation at 365 nm generates the interligand CT state which is a powerful oxidant with E(Rh* 3+/2+ ) of 2.0 V vs NHE, competent for direct oxidation of guanine in DNA to produce guanine radical 29,143. At higher energy excitation (308 nm), a ligand-centered state abstracts a sugar hydrogen to promote strand scission at the binding site of the metal complex 144. By comparing the sites of guanine damage induced by photoexcitation at these two wavelengths, the binding profile of the metal complex can be directly compared to the oxidative damage profile.…”

Section: Shuttling Of Oxidative Damagementioning

confidence: 99%

DNA-Mediated Charge Transport in Redox Sensing and Signaling

2010

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The transport of charge through the DNA base pair stack offers a route to carry out redox chemistry at a distance. Here we describe characteristics of this chemistry that have been elucidated and how this chemistry may be utilized within the cell. The shallow distance dependence associated with these redox reactions permits DNA-mediated signaling over long molecular distances in the genome and facilitates the activation of redox-sensitive transcription factors globally in response to oxidative stress. The long-range funneling of oxidative damage to sites of low oxidation potential in the genome also may provide a means of protection within the cell. Furthermore, the sensitivity of DNA charge transport to perturbations in base pair stacking, as may arise with base lesions and mismatches, may be used as a route to scan the genome for damage as a first step in DNA repair. Thus, the ability of double helical DNA, in mediating redox chemistry at a distance, provides a natural mechanism for redox sensing and signaling in the genome.

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Solution Photoreactivity of Phenanthrenequinone Diimine Complexes of Rhodium and Correlations with DNA Photocleavage and Photooxidation

Cited by 33 publications

References 29 publications

Using Metal Complex Reduced States to Monitor the Oxidation of DNA

Using Metal Complex Reduced States to Monitor the Oxidation of DNA

Long-range oxidative damage to cytosines in duplex DNA

DNA-Mediated Charge Transport in Redox Sensing and Signaling

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