Fluorescent labeling complexes with large stokes shift formed by coupling together cyanine and other flourochromes capable of resonance energy transfer

The present invention provides low molecular weight fluorescent labeling complexes with large wavelength shifts between absorption of one dye in the complex and emission from another dye in the complex. These complexes can be used, for example, for multiparameter fluorescence cell analysis using a single excitation wavelength. The low molecular weight of the complex permits materials labeled with the complex to penetrate cell structures for use as probes. The labeling complexes are synthesized by covalently attaching through linkers at least one cyanine fluorochrome to another low molecular weight fluorochrome to form energy donor-acceptor complexes. Resonance energy transfer from an excited donor to fluorescent acceptor provides wavelength shifts up to 300 nm. The fluorescent labeling complexes preferably contain reactive groups for the labeling of functional groups on target compounds, such as derivatized oxy and deoxy polynucleic acids, antibodies, enzymes, proteins and other materials. The complexes may also contain functional groups permitting covalent reaction with materials containing reactive groups.