Abstract:
The invention includes fusion polypeptides including a first fluorescent protein, e. g. , a FRET donor protein, a second fluorescent protein, e. g. , a FRET acceptor protein, and, linked to at least one of the fluorescent (e. g. , FRET donor or FRET acceptor) proteins, an Fc-region of an immunoglobulin. The polypeptide can be immobilized with respect to a surface via the Fc-region even in the absence of antibodies to either the FRET donor protein or FRET acceptor protein, and can be used as a calibration standard for fluorescence resonance energy transfer includes a polypeptide.