the emission wavelengths and allow dna sequencing with capillary electrophoresis using a single 488 nm excitation wavelength however the emission spectra overlap and there is residual emission from the donors which contributes to the intensities at shorter wavelengths hence there is still a need for improved dyes for dna sequencing a description of energy transfer primers for dna sequencing is disclosed in ju j ruan c fuller c w glazer a n and mathies r a u201c fluorescence energy transfer dye labeling primers for dna sequencing and analysis u201d proc natl acad sci usa 92 4347 51 1995 the possibility of using energy transfer primers for energy transfer probes allows one to obtain similar intensities at a single excitation wavelength in the case of the metal ligand complexes there is the additional advantage of the higher extinction coefficient of most organic chromophores compared with the metal ligand complexes hence sensitivity might be enhanced by using energy transfer from a high extinction coefficient dye to a long lifetime metal ligand complex to satisfy the demands of the human genome project it is necessary to sequence dna as inexpensively as possible one means of decreasing the cost is to use semiconductor laser diodes which are now available from 630 nm to longer wavelengths these lasers consume little power and can operate for up to 100 000 hours between failures an additional advantage of red and nir excitation is the lower autofluorescence from biological samples gels solvents and optical components it is difficult to obtain four dyes with similar absorption spectra and different emission spectra such dyes would allow determination of all four bases on a single gel column which is.