Femtosecond direct observation of charge transfer between bases in DNA

C. Wan, T. Fiebig, Olav Schiemann, JK. Barton, A. Zewail*

Research output: Contribution to journalArticlepeer-review

370 Citations (Scopus)


Charge transfer in supramolecular assemblies of DNA is unique because of the notion that the pi -stacked bases within the duplex may mediate the transport, possibly leading to damage and/or repair. The phenomenon of transport through pi -stacked arrays over a long distance has an analogy to conduction in molecular electronics, but the mechanism still needs to be determined. To decipher the elementary steps and the mechanism, one has to directly measure the dynamics in real time and in suitably designed, structurally well characterized DNA assemblies. Here, we report our first observation of the femtosecond dynamics of charge transport processes occurring between bases within duplex DNA. By monitoring the population of an initially excited 2-aminopurine, an isomer of adenine, we can follow the charge transfer process and measure its rate. We then study the effect of different bases next to the donor (acceptor), the base sequence, and the distance dependence between the donor and acceptor. We find that the charge injection to a nearest neighbor base is crucial and the time scale is vastly different: 10 ps for guanine and up to 512 ps for inosine. Depending on the base sequence the transfer can be slowed down or inhibited, and the distance dependence is dramatic over the range of 14 Angstrom. These observations provide the time scale, and the range and efficiency of the transfer. The results suggest the invalidity of an efficient wire-type behavior and indicate that long-range transport is a slow process of a different mechanism.

Original languageEnglish
Pages (from-to)14052-14055
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number26
Publication statusPublished - 19 Dec 2000




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