Patent ID: 7569355

Claim:
A luminescence energy transfer homogeneous bioassay comprising subjecting a first group labelled with an energy donor and a second group labelled with an energy acceptor to a reaction affecting the distance between said first group and said second group, wherein the donor is a luminescent lanthanide label which up-converts a lower-energy excitation to a higher-energy emission, the acceptor is either a luminescent or a non-luminescent label, and the increase or decrease, respectively, in energy transfer from the donor to the acceptor resulting from shortening or lengthening, respectively, of the distance between said labels is measured, wherein the assay is performed on a sample which comprises a biological fluid which absorbs radiation in the wavelength range 300 to 600 nm, the measurement of the acceptor emission or the donor emission is carried out at a wavelength >570 nm, and the donor label, which is excitable at wavelength longer than its emission wavelength, is excited at a wavelength longer than 600 nm.