Abstract: Binding assay reagents for use in optical assay systems are disclosed. Assays, such as immunoassays, employing the reagent are also disclosed. The reagent is comprised of paired, associated polypeptides one of which has multiple optically active dye labels. The binding assay reagents exhibit enhanced binding activity over that of the dye labelled polypeptides alone and also enhance the sensitivity of the binding assay by providing increased amounts of optical label.