Table 2. Antenna effect and end-to-end efficiency for the Cy3–Cy5 single-FRET step system.

			Relative Förster distance ( × R0)/predicted donor–acceptor separation
			0.75/40.5 Å	0.85/45.9 Å	1.0/54 Å	1.25/67.9 Å	1.5/81 Å
Construct	Cy3/Cy5	εCy3n/εCy5*	AE/E (%)	AE/E	AE/E	AE/E	AE/E
Linear	1	0.6	1.1/40	0.8/22	0.5/18	0.3/9	0.2/3
Bifurcated	2	1.2	1.9/51	1.3/28	0.8/20	0.6/10	0.3/4
Holliday junction	4	2.4	2.9/37	1.2/30	1.4/23	0.8/9	0.3/4
Eight-arm star	8	4.8	2.5/15	1.6/16	1.8/15	0.8/8	0.5/2

AE, antenna effect; E, end-to-end efficiency.

All values are collected from at least three independently assembled structures. S.d. for AE and E values from replicate experiments are all <10%.

^*Initial Cy3_n absorption at 550 nm relative to the final Cy5 absorption at 650 nm.