Table II.

Multiexponential Intensity Decay Analyses of the Donor (Ru-BD), Acceptor (BO-PRO-3), and Donor-Acceptor (DA) Pairs Bound to Calf Thymus DNA^a

Sample	Acceptor concentration (bp−1)	τ1	α1	SSI1	τ2	α2	SSI2	τ3	α3	SSI3	〈τ〉b	${\chi }_{\text{R}}^2$
Donor	0	157	0.41	0.71	46.0	0.59	0.29				124.0	1.4
Acceptor	0.09	4.4	1.00	1.00							4.4	1.2
DA	0.03	119	0.03	0.24	30.7	0.16	0.41	5.2	0.81	0.35	43.4	0.9
DA	0.06	114	0.02	0.19	30.0	0.16	0.41	5.8	0.82	0.40	35.6	0.8
DA	0.09	131	0.01	0.18	26.6	0.17	0.40	5.7	0.82	0.42	36.2	0.7

^aLED excitation was at 440 nm, and emission was observed at 640 ± 10 nm. There was no spectral separation between the donor and acceptor fluorescence.

^bMean lifetimes were calculated using 〈τ〉= f_i τ_i, where f_i is the fractional steady-state contribution of each component of the total emission.