Table 1.

Properties of rods from WT, GRK1-tg, and GRK7-tg zebrafish

	Property	Symbol	Units	WT	GRK1-tg	GRK7-tg
Physical	OS diameter	d	μm	2.9 ± 0.1 (19)	2.9 ± 0.1 (13)	2.9 ± 0.1 (43)
	OS length	L	μm	29.6 ± 1.2 (19)	29.2 ± 0.3 (13)	24.0 ± 0.6 (43)*
Electrical	Dark current = maximal response	iD=rmax	pA	5.5 ± 0.3 (39)	5.0 ± 0.3 (36)	5.9 ± 0.3 (55)
Response versus intensity	Half-saturating flash intensity	Q1/2	photons μm−2	6.8 ± 0.5 (39)	12 ± 1 (36)*	55 ± 6 (55)**
	Half-saturating photoisomerizations	ϕ1/2	photoisomerizations	16	29	110
Bright flash response kinetics	Dominant time constant	τdom, low	s	0.55 ± 0.03 (30)	0.59 ± 0.03 (26)	—
				0.57	0.41	0.54
		τdom, med	s	0.95	0.92	0.96
		τdom, high	s	7.5	4.1	6.1
Dim flash response kinetics	Time-to-peak	tpeak	s	0.57 ± 0.02 (39)	0.54 ± 0.02 (32)	0.84 ± 0.04 (54)*
	Integration time	tint	s	0.88 ± 0.04 (39)	0.88 ± 0.04 (33)	1.60 ± 0.07 (55)*
	Decay time constant	τrec	s	0.55 ± 0.04 (39)	0.53 ± 0.03 (32)	1.10 ± 0.05 (54)*
Single-photon response amplitude	From half-saturation intensity	amacro	pA	0.23†	0.12†	0.04†
	From variance	avar	pA	0.32 ± 0.02 (23)	0.19 ± 0.02 (11)*†	0.32 ± 0.03 (14)†
	From amplitude histogram	ahistog	pA	0.32 ± 0.03 (9)	—	0.27 ± 0.02 (14)†
	Two-component analysis	aL	pA	—	—	0.34 ± 0.02 (5)
	Two-component analysis	aS	pA	—	—	0.022 ± 0.005 (5)
Effective collecting area	Physical	Ac	μm2	2.4	2.4	2.0
	Functional	Ac	μm2	1.95 ± 0.14 (23)	1.57 ± 0.24 (11)	0.32 ± 0.07 (5)
Amplification constant	From single-photon response	ASPR	s−2	1.5 ± 0.2 (23)	1.1 ± 0.2 (11)	0.9 ± 0.1 (17)*
	From flash family	Afamily	s−2	2.6 ± 0.3 (23)	1.6 ± 0.2 (11)*	1.2 ± 0.2 (17)*

Physical properties and electrical response properties measured for rods of the three genotypes. Values are given as means ± SEM, except for derived values which are given without error estimates. Statistically significant differences of means from WT values are indicated: *P < 0.05; **P < 0.01. Significance was determined using Student's t test for unpaired observations; the number (n) of observations represents the number of rods tested. —: not measured. For the dominant time constant, the first row (with SEM) gives the means of the individual fits (for the lowest range of saturating intensities), whereas the values without SEM are for the slopes of the pooled data. For single-photon response amplitudes, measurements indicated † need to be treated with caution. The macroscopic values rely on the accuracy of the light intensity calibrations and on the accuracy of the calculation of effective collecting area; the values of a_macro for WT and GRK1-tg are about 2/3 of the estimates a_var and a_histog from variance and histogram measurements, which suggests that the actual numbers of isomerizations may have been lower than calculated from the light intensities (see Results). For GRK7-tg rods, the only estimates of single-photon response amplitude that can be considered reliable are those obtained by the two-component analysis approach.