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Fluorescent Excimers and Exciplexes of the Purine Base Derivative 8-Phenylethynyl- guanine in DNA Hairpins

Abstract

The ground- and excited-state electronic interactions between the nucleobase analog 8 (4' phenylethynyl)deoxyguanine, EG, with the natural nucleobases and 7-deazaguanine as well as between adjacent EG base analogs have been characterized using a combination of steady-state spectroscopy and time-resolved fluorescence, absorption, and stimulated Raman spectroscopies. The properties of the nucleoside EG-H2 are only weakly perturbed upon incorporation into synthetic DNA hairpins in which thymine, cytosine, or adenine are the bases flanking EG. Incorporation adjacent to guanine or deazaguanine results in the formation of short-lived (40-80 ps) exciplexes, the charge transfer character of which increases as the oxidation potential of the donor decreases. Hairpins having two or three adjacent EG base analogs display exciton-coupled circular dichroism in the ground state and form long-lived fluorescent excited states upon electronic excitation. Incorporation of EG into the helical scaffold of the DNA hairpins places it adjacent to its neighboring nucleobases or a second EG thus providing the close proximity required for the formation of exciplex or excimer intermediates upon geometric relaxation of the short-lived EG excited state. The three time-resolved spectroscopic methods employed permit both the characterization of the several intermediates and the kinetics of their formation and decay.

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Publication details

The article was accepted on 01 Sep 2017 and first published on 01 Sep 2017


Article type: Paper
DOI: 10.1039/C7FD00186J
Citation: Faraday Discuss., 2017, Accepted Manuscript
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    Fluorescent Excimers and Exciplexes of the Purine Base Derivative 8-Phenylethynyl- guanine in DNA Hairpins

    K. E. Brown, A. Singh, Y. Wu, L. Ma, A. K. Mishra, B. T. Phelan, R. M. Young, F. D. Lewis and M. R. Wasielewski, Faraday Discuss., 2017, Accepted Manuscript , DOI: 10.1039/C7FD00186J

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