Patent ID: 8143013

Claim:
A biological imaging method comprising the steps of applying a bioactive substance labeled with Cypridina luciferase and an organic fluorescent dye to a living body; the bioactive substance being at least one species selected from the group consisting of antibodies, antigens, haptens, hormones, ligands for receptors and ion channels, and detecting a fluorescence maximum in the range of 650 nm and 750 nm resulting from bioluminescence resonance energy transfer between the Cypridina luciferase and the organic fluorescent dye, wherein the organic fluorescent dye has a fluorescence maximum (λmax) in the range of 400 nm and 700 nm by irradiation from an external excitation light source, wherein said organic fluorescent dye is bonded to Cypridina luciferase through the sugar chain of Cypridina luciferase and wherein said bioactive substance are linked together.