Table 2.

Some of the main optogenetic tools for sensing cellular activity.

Protein	Excitation/emission wavelengths (nm)	Action	References
(a) Voltage sensors
FlaSh	450/510	Voltage sensor	44
VSFP1	440/480 and 530	Voltage sensor	45
VSFP2.3	440/480 and 530	Voltage sensor	46
SPARC	470/500 to 550	Voltage sensor	47
hVOS	480/520	Voltage sensor	48
ElectricPK	485/510	Voltage sensor	49
ArcLight	485/510	Voltage sensor	50
PROPS	550/700	Voltage sensor	51
Arch	560/690	Voltage sensor	41
Arch(D95N)	585/690	Voltage sensor	41
QuasAr1/QuasAr2	590/715	Voltage sensor	26
Archer1/Archer2	$655/>680$	Voltage sensor	33
MacQ-mCitrine	500/530 and 580	Voltage sensor	52
MacQ-mOrange2	530/560 and 580	Voltage sensor	52
Citrine eFRET GEVI (QuasAr2)	500/530 and 715	Voltage sensor	53
mOrange2 eFRET GEVI (QuasAr2)	530/560 and 715	Voltage sensor	53
mRuby2 eFRET GEVI (QuasAr2)	560/600 and 715	Voltage sensor	53
(b) Calcium sensors
GCaMPs	490/510	Calcium sensor	43,54
RCaMPs	570/585	Calcium sensor	55
G-Gecos	490/510	Calcium sensor	42,56
B-Gecos	375/450	Calcium sensor	42
R-Gecos	565/585	Calcium sensor	42
Twitch	435/470 and 530	Calcium sensor	57
GEM-GECO1	400/450 and 510	Ratiometric calcium sensor	42
GEX-GECO1	400 and 480/510	Ratiometric calcium sensor	42
REX-GECO1	480 and 570/585	Ratiometric calcium sensor	58
Cameleon derivatives (YCs)	435/470 and 530	Ratiometric calcium sensor	59
TN-XXL	435/480 and 530	Calcium sensor	60
(c) Others
FLIP-E	435/480 and 530	Glutamate sensor	61
iGluSnFrs	485/510	Glutamate sensor	62
Chlomeleon/Super Chlomeleon	435/470 and 530	Ratiometric chloride sensor	63,64
CNiFER	435/480 and 530	Acetylcholine sensor	65
pHRed	440 and 580/610	Ratiometric pH sensor	66
SE-pHluorin	400 and 475/510	pH sensor	67
pHuji	570/600	pH sensor	67
Perceval	405 and 490/530	ATP/ADP sensor	68
HyPer	430 and 500/520	${\mathrm{H}}_2{\mathrm{O}}_2$ sensor	69