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. Author manuscript; available in PMC: 2017 Aug 15.
Published in final edited form as: Nat Neurosci. 2016 Aug 26;19(9):1142–1153. doi: 10.1038/nn.4359

Table 4.

Selected genetically encoded voltage indicators (GECIs)

GECI Maximum ΔF/F
in vitroa 		Ca2+-free
brightness
(mM−1 cm−1)b 		Ca2+-saturated
brightness
(mM−1 cm−1)b 		Kd in
vitro
(nM)c 		ΔF/F
per AP in
tissued 		Half-decay rate
in tissue
(ms)e 		Refs.
YC3.60 −0.66 (ECFP) 8.8f 3.1 780 −0.01 410 137,138
+0.77 (cpVenus) 2.4f 11 +0.02
YC3.60 −0.66 (ECFP) 8.8g 3.1 140 −0.01f 470 139,140
3GS +0.77 (cpVenus) 2.4g 11 +0.01f
D3cpV −0.46 (ECFP) 7.3h 3.6 530 −0.03f 9,500 141,142
+1.1 (cpVenus) 4.8h 10 +0.02f
TN-XXL −0.5 (ECFP) 9.6i 5.4 800 −0.01f 1,600 142,143
+1.0 (cpCitrine) 1.5i 10 +0.02f
Twitch-2B −0.77 (mCerulean3) 22j 5.8 200 −0.12f 2,100 82,142
+0.87 (cpVenus) 0.83j 12 +0.12f
GCaMP3 +12 1.8 23 540 +0.14 650 114,142
GCaMP5k +9.4 ND ND 190 +0.04 270 72,144
GCaMP6f +52 0.70 37 380 +0.22 140 72,91
GCaMP6s +63 0.66 42 140 +0.25 550 72
R-CaMP2 +4.8 2.3 (1.6)k 11 69 +0.60 150 106
jRGECO1a +11 1.0 (0.74)k 12 150 +0.19 200 7
jRCaMP1b +6.2 4.0 (4.0)k 29 712 NDl ND 7

GECIs with reported single-AP responses in live animals or acute rodent slices are included. Some values are estimates based on published graphs.

a

Fluorescence change from zero to saturating calcium in vitro at 25 °C at the emission peak of each channel. This number is empirically measured and, for the acceptor fluorophore in FRET sensors, is influenced by cross-excitation and bleed-through. As event detection is often optimized by single-channel imaging of FRET indicators23,83, the two channels are shown separately.

b

Estimated molar brightness produced by each fluorophore. For FRET sensors, brightness for the donor channel is calculated as the product of donor peak extinction coefficient and donor quantum yield multiplied by 1 – E, where E is measured FRET efficiency in calcium-free or calcium-saturated conditions. Brightness for the acceptor channel is calculated as the product of donor peak extinction coefficient and acceptor quantum yield multiplied by E. Values for specific parameters are noted below. Values do not account for any cross-excitation or bleed-through, but provide an estimate of the contribution of each fluorophore to indicator brightness. For single-protein sensors, calcium-free brightness is calculated from calcium-saturated fluorescence and maximum ΔF/F.

c

Measured at 25 °C.

d

In mouse brain or mouse acute slices at 35 °C.

e

In vitro measurements at 37 °C; neuronal measurements in mouse brain or mouse acute slices at 35 °C in response to a single AP.

f

Peak ECFP extinction coefficient is 28 mM−1 cm−1 at 433 nm, ECFP quantum yield is 0.37 (ref. 129), cpVenus quantum yield is assumed to be 0.57 as with Venus130, and calcium-free/saturated E of 0.15/0.70 is derived from published emission spectra as previously described131,132.

g

FRET emission spectra are not published, but E values are inferred to be similar to that of YC3.60 on the basis of similar ratio changes.

h

Calcium-free/saturated E of 0.30/0.65 is derived from published emission spectra.

i

Citrine quantum yield is 0.76 (ref. 130), calcium-free/saturated E of 0.07/0.48 is derived from calcium-free/saturated emission spectrum (A.J. Lam and M.Z.L., unpublished data).

j

Peak mCerulean3 extinction coefficient is 29 mM−1 cm−1 at 433 nm, Cerulean quantum yield is 0.80 (ref. 135), and calcium-free/saturated E of 0.05/0.75 is derived from published emission spectra.

k

Values in parentheses are from direct measurement of extinction coefficient and quantum yield without calcium. ND, not determined.