Fluorescence Behavior and Energy Transfer of Cyanine Dyes Bound to Bilayer Membranes of Double-Chain Ammonium Amphiphiles

Negatively-charged cyanine dyes are bound specifically to aqueous bilayer membranes of double-chain ammonium amphiphiles, as reflected in their absorption spectra. The quantum yield of the fluorescence emission of a trimethine-thiacyanine dye is remarkably enhanced (up to 0.64) when the dye is bound to crystalline bilayer membranes of certain double-chain ammonium amphiphiles. The fluorescence intensity diminished drastically with the liquid crystalline bilayers. Efficient energy transfer is noted from an oxacyanine to the thiacyanine dye in the crystalline membrane matrix. The efficiency decreases by the membrane phase transition to the liquid crystalline state. These results are discussed in terms of specific dye binding and concentration of dyes at the membrane surface.