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Proceedings Paper

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

Two- and three-photon excitation was used to investigate the properties of two fluorescent DNA base analogs: 2-aminopurine and 6-methylisoxanthopterin. 2-aminopurine is a widely used fluorescent analog of the DNA base adenine. Three-photon excitation of 2-aminopurine is achievable by using intense femtosecond laser pulses in 850-950 nm spectral region. Interestingly, the three-photon excitation spectrum is blue-shifted relative to the three-times-wavelength single-photon excitation spectrum. The maximum of the absorbance band in the UV is at 305 nm, while the three-photon excitation spectrum has a maximum at around 880 nm. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2-aminopurine for DNA-protein interaction studies. However, due to relatively small three-photon absorption cross-section, a good signal-to-noise fluorescence correlation curves take very long time to obtain. Fluorescence properties of 6-methylisoxanthopterin, the fluorescent analog of guanine, were investigated using two-photon excitation. This molecule has the lowest energy absorption band centered around 350 nm, thus, two-photon excitation is attainable using 700 to 760 nm output of Ti-sapphire laser. The excitation spectrum of this molecule in the infrared well matches the doubled-wavelength single-photon excitation spectrum in the UV. The high fluorescence quantum yield of 6-methylisoxanthopterin allows efficient fluorescence correlation measurements and makes this molecule a very good candidate for using in in vitro DNA-protein interaction studies.

Paper Details

Date Published: 21 June 2004
PDF: 8 pages
Proc. SPIE 5323, Multiphoton Microscopy in the Biomedical Sciences IV, (21 June 2004); doi: 10.1117/12.529853
Show Author Affiliations
Evaldas Katilius, Arizona Biodesign Institute/Arizona State Univ. (United States)
Neal W. Woodbury, Arizona Biodesign Institute/Arizona State Univ. (United States)

Published in SPIE Proceedings Vol. 5323:
Multiphoton Microscopy in the Biomedical Sciences IV
Ammasi Periasamy; Peter T. C. So, Editor(s)

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