Multi-photon excitation fluorescence correlation spectroscopy of fluorescent DNA base analogs

Evaldas Katilius, Neal Woodbury

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


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.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsA. Periasmy, P.T.C. So
Number of pages8
StatePublished - 2004
EventProgress in Biomedical Optics and Imaging - Multiphoton Microscopy in the Biomedical Sciences IV - San Jose, CA, United States
Duration: Jan 25 2004Jan 27 2004


OtherProgress in Biomedical Optics and Imaging - Multiphoton Microscopy in the Biomedical Sciences IV
Country/TerritoryUnited States
CitySan Jose, CA


  • 2-aminopurine
  • 6-methylisoxanthopterin
  • Fluorescence correlation spectroscopy
  • Fluorescent DNA base analogs
  • Multi-photon excitation

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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