HTRF

(= homogeneous time-resolved fluorescence)

Assay methodology increasingly being used in high throughput screening. An absorbing fluorochrome is coupled to one component, the emitting fluorochrome with slow-release characteristics coupled to the other and if the two components are in proximity (because they bind) then fluorescence resonance energy transfer between absorbing and emitting fluorochromes gives a signal which is analysed in a time-resolved fluorescence system. No separation step is required - all the reagents are mixed together and inhibitors of binding will reduce the output signal.