Two-photon excitation of ethidium bromide labeled DNA

Biophys Chem. 1997 Sep 1;67(1-3):35-41. doi: 10.1016/s0301-4622(97)00017-3.


We examined the steady state and time-resolved emission of DNA stained with ethidium bromide (EB) when excited with 90 fs pulses from a mode-locked titanium sapphire laser. Over the wavelength range from 840 to 880 nm EB-DNA was found to display two-photon excitation, with a cross-section near 7 x 10(-50) cm4s/photon. Frequency-domain intensity decay measurements revealed similar multi-exponential intensity decays for one- and two-photon excitation. Time-resolved anisotropy decay measurements revealed similar correlation times, but different amplitudes as has been observed previously for two- versus one-photon excitation. These results indicate that two-photon excitation of EB-DNA can be accomplished with the fundamental output of a Ti:sapphire laser without obvious heating or perturbation of the DNA.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cattle
  • DNA / chemistry*
  • Ethidium / chemistry*
  • Fluorescence Polarization
  • Photons*
  • Spectrometry, Fluorescence / methods


  • DNA
  • Ethidium