Multistep fluorescence resonance energy transfer in sequential chromophore array constructed on oligo-DNA assemblies.

Abstract

Sequential arrays of chromophores at regulated distances were constructed on a noncovalent DNA molecular assembly system in aqueous media. Photoinduced fluorescence resonance energy transfer (FRET) behaviors were then observed. We designed a number of chromophore/oligo-DNA conjugates with varying sequences. The chromophores eosin (Eo), TexasRed (TR), and tetramethylrhodamine (Rho) were employed as the energy donor, acceptor, and mediator, respectively, based on overlapping excitation and emission spectra. The chromophores were attached via aminolinkers to the 5'-terminals of 10mer oligo-DNAs consisting of AT rich sequences. The arrangement of Eo-Rho or Rho-TR with 10-residue (1 pitch of duplex) distances was ensured by duplex formation of the conjugates with a 20mer matrix oligo-DNA composed of complementary sequences to the conjugates. Single-step FRET from Eo to Rho and from Rho to TR was confirmed on the duplex. The three chromophore conjugates were then mixed with longer matrix oligo-DNAs (30 or 40mer) consisting of complementary sequences to the conjugates, producing Eo-(Rho)(n)-TR (n = 1 or 2) arrays with 10-residue distances. Multistep FRET from Eo to TR through the Rho mediator(s) was observed on the molecular assemblies. This photoenergy transmission system offers a good model for a photoenergy transmission system mimicking photosynthetic systems.