Table 2. Measurement of fluorescence lifetime by fluorescent lifetime imaging.

Donor*	Acceptor*	Fluorescence lifetime (ns) (means±S.D.)†
ECFP-S100A1	S100P-EYFP	1.55±0.33
ECFP-S100A1	EYFP	2.63±0.25
ECFP-S100A1	None	2.47±0.11
ECFP-S100A1	S100A1-EYFP	1.44±0.36

* HeLa cells that co-express donor and acceptor proteins were used for the measurement of fluorescence lifetime.

† Means±S.D. from 7 to 12 cells for two independent transfections. The fluorescent lifetimes measured from the cells co-expressing ECFP-S100A1 and S100P-EYFP and from the cells co-expressing ECFP-S100A1 and S100A1-EYFP are similar (P=0.374, Student's t test) but significantly shorter than that of the cells co-expressing ECFP-S100A1 and EYFP (P=0.001 and P=0.003 respectively) or the cells expressing ECFP-S100A1 only (P=0.001 and P=0.002 respectively). The fluorescent lifetimes measured of the cells co-expressing ECFP-S100A1 and EYFP and the cells expressing ECFP-S100A1 only are similar (P=0.231).