Patent ID: 7998749

Claim:
A method for determining whether two or more molecular features in a sample are in proximity, the method comprising: a) contacting in said sample, a first molecular feature labeled with a donor fluorophore having a first absorption spectrum and a first emission spectrum, and a second molecular feature labeled with an acceptor fluorophore having a second absorption spectrum overlapping with the first emission spectrum and a second emission spectrum; wherein said first molecular feature and said second molecular feature are on different molecules; b) exciting said donor fluorophore with plane polarized light at a wavelength within said first absorption spectrum, thereby resulting in transfer of the excited state energy from the donor to the acceptor fluorophore by intermolecular long-range dipole-dipole coupling, and subsequent emission of fluorescence from the acceptor fluorophore at a wavelength from within said second emission spectrum; c) detecting polarization of fluorescence emitted by said acceptor fluorophore at a wavelength within said second emission spectrum; and d) correlating a change in polarization of fluorescence emitted by said acceptor fluorophore with a change in proximity of the first and second molecular features to each other, said change relative to the polarization fluorescence emitted by said acceptor fluorophore from either the same sample at a different time or from a control.