TABLE 3.

FRET^a

Donor	Acceptor	nc	% FRET efficiencyb
			Nucleolus	Nucleoplasm	Cajal bodies
ECFP	EYFP	3	None present	1.6 ± 2.8	None present
ECFP	Meq/vIL8-EYFP	3	−2.2 ± 0.2	−3.0 ± 1.3	None present
Meq/vIL8-ECFP	EYFP	5	0.7 ± 2.0	−2.1 ± 3.8	None present
Meq/vIL8-ECFP	Meq/vIL8-EYFP	3	14.1 ± 2.0	11.4 ± 3.3	7.5 ± 1.5

^aResonance energy transfer was measured by the acceptor photobleaching method. Initial fluorescence intensities were recorded from ECFP and EYFP constructs, and then EYFP fluorescence was photobleached using 514-nm excitation light.

^bThe percentage of FRET efficiency (E) was determined by the equation E = (I_A − I_B)/I_A, where I_A and I_B are the ECFP fluorescence intensities after and before EYFP photobleaching, respectively. None present, these combinations of donor and acceptor were not found. A negative value for FRET efficiency arises from slight drift during data collection.

^cn, number of measurements.