Abstract: Ligand-aminodextran-(phycobiliprotein or tandem dye) conjugates useful for detection of a desired target biological material by providing an enhanced fluorescent signal are described. Also described is a method for a single-measurement quantification of multiple populations of cells based upon the labeling of different pairs of cell populations, each pair containing mutually exclusive cell receptors which are expressed at substantially similar receptor densities with labeled ligands for each receptor. One cell population is labeled with a ligand capable of binding to a first cell surface receptor which ligand is directly conjugated to a fluorescent phycobiliprotein or tandem dye; and a second cell population is labeled with a ligand capable of binding to a second cell surface receptor, which ligand is cross-linked to an aminodextran to a fluorescent phycobiliprotein or tandem dye.

Abstract: The present application discloses dextran crosslinked, antibody-phycobiliprotein conjugates containing up to twenty phycobiliprotein per dextran molecule which conjugates are able to achieve amplification of fluorescence intensity over direct antibody-phycobiliprotein labeled cells of two fold or greater.