Table 1.

Photophysical properties of the taxoid-pyrazolines and fluorescence turn-on efficiency^a

Com- pound	λmax b (nm)	εc (M−1cm−1)	ε405d (M−1cm−1)	λem (nm)	ΦFe	Fluorescence turn-onf
1	310	6,400	460	ND	ND	-
1a	330	5,100	2,000	617	0.0024	21-fold
1ag	340	4,400	1,600	580	0.036	34-fold
2	311	12,000	540	ND	ND	-
2a	332	8,700	3,000	614	0.0041	30-fold
2ag	344	11,600	4,700	587	0.022	101-fold
3	262h	24,400	ND	ND	ND	-
3a	358	12,900	6,900	584	0.034	111-fold
4	276h	30,300	ND	ND	ND	-
4a	336	16,400	3,100	528	0.056	112-fold

^aCompounds were dissolved in ACN/PBS (1:1) to derive concentrations of 25 µM unless noted otherwise.

^bλ_max in the 300 ~ 500 nm region.

^cExtinction coefficient at λ_max.

^dExtinction coefficient at 405 nm.

^eQuantum yields were measured using DAPI as a standard (see ref. 20), and integrated over 415–790 nm.

^fObtained by comparing the emission intensities at λ_em; λ_ex = 405 nm.

^gDissolved in DCM.

^hλ_max in the 250 ~ 500 nm region.

ND = not detected.