Table 1. Properties of selected M739-based DiBs.

Pair name	Mutations a	λ ex, nm	λ em, nm	FQY b , %	EC, M–1 cm–1	λ-Dependent FI, fold c	K d, μM	Photostability (relative to) d
DiB1	A36C/L141N	513	542	32	45 800	52	0.1	2× (EGFP)
DiB2	A36C	510	539	32	51 000	64	4	6× (EGFP)
DiB3	V74F/L141Q	546	565	15	43 000	11	9	10× (mKate)
Free M739	N/A	520	563	3.5	53 500	N/A

^aFor numbering and sequence information refer to ESI Fig. 1.†

^bFluorescence quantum yield.

^cFluorescence increase compared to free M739 under conditions of confocal or TIRF microscopy (excitation at 488 nm and detection at 500–530 nm for DiB1 and DiB2; excitation at 561 nm and detection at 580–620 nm for DiB3).

^dSee Fig. 2.