Table 1.

Definition of the variables used to perform BRET imaging

Terminology	Definition
em480	Light emission at 450–510 nm, corresponding to Rluc emission peak at 480 nm.
em535	Light emission at 510–560 nm, corresponding to the YFP emission peak at 535 nm
535 nm /480 nm ratio	Pixel-by-pixel ratio calculated by dividing the absolute intensities per pixel of images obtained at 535 nm over 480 nm
Average intensity	Mean intensity of pixels within a square region drawn on the cell of interest before image analysis
Background	Mean intensity of pixels within a square region drawn in a surface without cells before image analysis
Signal/background	Ratio corresponding to the previous average intensity signal over the background signal recorded in two adjacent equal surfaces
Basal 535 nm/480 nm ratio	535 nm/480 nm ratio obtained in the presence of Rluc and absence of acceptor entity. Corresponds to the overflow of the Rluc output into the YFP acceptor detection channel