A Caltech Library Service

Direct Chemical Evidence for Charge Transfer between Photoexcited 2-Aminopurine and Guanine in Duplex DNA

O'Neill, Melanie A. and Dohno, Chikara and Barton, Jacqueline K. (2004) Direct Chemical Evidence for Charge Transfer between Photoexcited 2-Aminopurine and Guanine in Duplex DNA. Journal of the American Chemical Society, 126 (5). pp. 1316-1317. ISSN 0002-7863. doi:10.1021/ja037802p.

[img] PDF (HPLC traces profiling photodecomposition of ^(CP)G in Ap-containing DNA duplexes, duplex melting temperatures, and emission and excitation spectra) - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


Photoexcited 2-aminopurine (Ap*) is extensively exploited as a fluorescent base analogue in the study of DNA structure and dynamics. Quenching of Ap* in DNA is often attributed to stacking interactions between Ap* and DNA bases, despite compelling evidence indicating that charge transfer (CT) between Ap* and DNA bases contributes to quenching. Here we present direct chemical evidence that Ap* undergoes CT with guanine residues in duplex DNA, generating oxidative damage at a distance. Irradiation of Ap in DNA containing the modified guanine, cyclopropylguanosine (^(CP)G), initiates hole transfer from Ap* followed by rapid ring opening of the ^(CP)G radical cation. Ring opening accelerates hole trapping to a much shorter time regime than for guanine radicals in DNA; consequently, trapping effectively competes with back electron transfer (BET) leading to permanent CT chemistry. Significantly, BET remains competitive, even with this much faster trapping reaction, consistent with measured kinetics of DNA-mediated CT. The distance dependence of BET is sharper than that of forward CT, leading to an inverted dependence of product yield on distance; at short distances product yield is inhibited by BET, while at longer distances trapping dominates, leading to permanent products. The distance dependence of product yield is distinct from forward CT, or charge injection. As with photoinduced charge transfer in other chemical and biological systems, rapid kinetics for charge injection into DNA need not be associated with a high yield of DNA damage products.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Barton, Jacqueline K.0000-0001-9883-1600
Additional Information:© 2004 American Chemical Society. Received August 7, 2003. Publication Date (Web): January 20, 2004. We gratefully acknowledge the NIH (GM49216) and NFCR. M.A.O. and C.D. thank NSERC, and the JSPS, respectively, for postdoctoral fellowships.
Funding AgencyGrant Number
National Foundation for Cancer ResearchUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20160208-163052817
Persistent URL:
Official Citation:Direct Chemical Evidence for Charge Transfer between Photoexcited 2-Aminopurine and Guanine in Duplex DNA Melanie A. O'Neill, Chikara Dohno, and Jacqueline K. Barton Journal of the American Chemical Society 2004 126 (5), 1316-1317 DOI: 10.1021/ja037802p
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64322
Deposited By: George Porter
Deposited On:09 Feb 2016 20:58
Last Modified:10 Nov 2021 23:29

Repository Staff Only: item control page