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Journal of Biomedical Optics

Multiphoton excitation of fluorescent DNA base analogs
Author(s): Evaldas Katilius; Neal W.T. Woodbury
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Paper Abstract

Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5×10–50 cm4s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.

Paper Details

Date Published: 1 July 2006
PDF: 7 pages
J. Biomed. Opt. 11(4) 044004 doi: 10.1117/1.2337521
Published in: Journal of Biomedical Optics Volume 11, Issue 4
Show Author Affiliations
Evaldas Katilius, Arizona State Univ. (United States)
Neal W.T. Woodbury, Arizona State Univ. (United States)


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