Chemically reactive dyes that are intramolecularly crosslinked with a water-soluble bridge, their bioconjugates and their uses are described. Reactive fluorescent dyes that have a water-soluble bridge are superior to those of conjugates of spectrally non-crosslinked dyes or the dyes that are crosslinked with a hydrophobic bridge. The invention includes reactive fluorescent dyes, their biological conjugates and uses.
