fluorescence technology protein complementation assay bimolecular fluorescence complementation bifc MI:0809 gfp complementation The bimolecular fluorescence complementation (BiFC) is an assay for determination of protein interactions and/or their location in living cells. This approach is based on complementation between two non- fluorescent fragments of a protein fluorophore such as green fluorescent protein (GFP) or its derivatives. Interactions between proteins fused to each fragment bring the fragments together resulting in the reconstitution of a fully functional flourophore that can be identified through fluorescence spectroscopy or microscopy. PSI-MI MI:0229 green fluorescence protein complementation assay