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Published February 24, 2003 | public
Journal Article

5' Modification of Duplex DNA with a Ruthenium Electron Donor−Acceptor Pair Using Solid-Phase DNA Synthesis

Abstract

Incorporation of metalated nucleosides into DNA through covalent modification is crucial to measurement of thermal electron-transfer rates and the dependence of these rates with structure, distance, and position. Here, we report the first synthesis of an electron donor−acceptor pair of 5' metallonucleosides and their subsequent incorporation into oligonucleotides using solid-phase DNA synthesis techniques. Large-scale syntheses of metal-containing oligonucleotides are achieved using 5' modified phosporamidites containing [Ru(acac)_2(IMPy)]^(2+) (acac is acetylacetonato; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (3) and [Ru(bpy)_2(IMPy)]^(2+) (bpy is 2,2'-bipyridine; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (4). Duplexes formed with the metal-containing oligonucleotides exhibit thermal stability comparable to the corresponding unmetalated duplexes (T_m of modified duplex = 49 °C vs T_m of unmodified duplex = 47 °C). Electrochemical (3, E_(1/2) = −0.04 V vs NHE; 4, E_(1/2) = 1.12 V vs NHE), absorption (3, λ_(max) = 568, 369 nm; 4, λ_(max) = 480 nm), and emission (4, λ_(max) = 720 nm, τ = 55 ns, Φ = 1.2 × 10-4) data for the ruthenium-modified nucleosides and oligonucleotides indicate that incorporation into an oligonucleotide does not perturb the electronic properties of the ruthenium complex or the DNA significantly. In addition, the absence of any change in the emission properties upon metalated duplex formation suggests that the [Ru(bpy)_2(IMPy)]^(2+)[Ru(acac)_2(IMPy)]^(2+) pair will provide a valuable probe for DNA-mediated electron-transfer studies.

Additional Information

© 2003 American Chemical Society. Received 4 March 2002. Published online 21 January 2003. Published in print 1 February 2003. We thank Dr. Suzanna Horvath for the use of the DNA Synthesis Facility, and BILRC for their expertise and the use of the NSI laser system. This work was supported by NIST (ATP) Award 70NANB5H1031, Jet Propulsion Laboratory (JPL 67192), and the Beckman Institute Biological Imaging Center. N.L.F. thanks the NIH for a Postdoctoral Fellowship (NRSA Grant F32 GM 20016-2).

Additional details

Created:
August 19, 2023
Modified:
October 25, 2023