Table 1.

FRET-FLIM analysis of interactions between HP1α and C/EBPα.

Expressed proteins	$n_{\mathrm{cell}}$a	$n_{\mathrm{ROI}}$b	$I_A/I_D$c (range)	$E_{\mathrm{FRET}}$d (range)	$E_{\mathrm{FRET}}\max$e
Cer3-C/EBPα + Venus-BZip	23	184	1.8 to 21	1.3 to 22.3%	$23.5\pm 1.7\%$
Turquoise-BZip + Venus-HP1α	13	128	2 to 35.2	2 to 22%	$15.8\pm 0.9\%$
Turquoise-BZip + Venus-HP1W174A	12	117	3 to 34.7	3 to 20%	$16.4\pm 1.7\%$
Turquoise-BZip + Venus-HP1W41A	12	120	3 to 19.8	0 to 15%	NDf
TurquoiseN1 + Venus-HP1α	13	26	1.2 to 8.4	$-2.7$ to 1.5	ND

^aNumber of individual cells analyzed for that FRET pair.

^bTotal number of cellular ROI analyzed for that FRET pair.

^cThe range of $I_A/I_D$ ratios measured in all ROI for that FRET pair.

^dThe range of FRET efficiencies (%) measured in all ROI for that FRET pair. $E_{\mathrm{FRET}}$ was determined using Eq. (1) (see text).

^eThe $E_{\mathrm{FRET}}\max$ was determined from the nonlinear regression for saturation binding (see Fig. 2);

^fND: not determined.