TABLE 1.

Relation of FRET indices to E_max and degrees of molecular interaction

Method (assuming b = c = 0)	Relation to Emax, χD, χA	Type 1 experiment (k = const):	Type 3 experiment (k ≠ const):		Reference
		Follows degree of interaction?	Follows donor occupancy?	Follows acceptor occupancy?
Sensitized fluorescence
	RDDGEmaxχD[Dtotal]	No	No	No	Youvan et al. (1997)
Group 1 ratios
		Yes,*NL	No	No	Miyawaki et al. (1997)
		Yes,*NL	Yes,*NL	No	Vanderklish et al. (2000)
		Yes,*NL	Yes,*NL	No	Zal et al. (2002)
Group 2 ratios
		Yes,*L	No	Yes,*L	Jiang and Sorkin (2002)
		Yes,*L	No	Yes,*L	Erickson et al. (2001)
Group 3 ratios
		No	No	No	Gordon et al. (1998)
	GEmaxχD/((1–EmaxχD)k)1/2	Yes,*NL	No	No	Xia and Liu (2001)
E-FRET method
	EmaxχD	Yes,*L	Yes,*L	No	This article
		Yes, L	Yes, L	No
or

Published formulae were translated to symbols used in this article. The dependence of each index on E_max, χ_D, and χ_A was derived in Appendix. See Appendix: Glossary for definition of acronyms and symbols.

^*Only if imaging-induced photobleaching is negligible.