Table 1.

Characteristics of far-red and NIR GECIs in comparison with widely used GCaMP6s.

GECI name	Ex/Em (nm)	Molecular brightness vs. EGFP, % ⁽¹⁾		pK_{a apo,} pK_{a sat,}	Photostability t_0.5, s ⁽²⁾		Effective brightness, % ⁽³⁾		Dynamic range (ΔF/F), fold	Hill coefficients n₁ and n₂	Rise time, s ⁽⁴⁾	Decay time, s ⁽⁴⁾	K_d1 and K_d2, nM	ΔF/F, % per 1 AP		Ref
GECI name	Ex/Em (nm)	w/o Ca²⁺	with Ca²⁺	pK_{a apo,} pK_{a sat,}	HeLa cells	mouse neurons	w/o BV	with BV	Dynamic range (ΔF/F), fold	Hill coefficients n₁ and n₂	Rise time, s ⁽⁴⁾	Decay time, s ⁽⁴⁾	K_d1 and K_d2, nM	in neurons	in vivo	Ref
iGECI	Donor 640/670	37	6.0	4.5, 4.5	1795	1735	46	100	6×	2.5 and 0.90	0.70	14	15 and 890	−5.7 (−12.9 with BV)	∼ −5–20	²⁷
iGECI	Acceptor 702/720	37	6.0	4.5, 4.5	1795	1735	46	100	6×	2.5 and 0.90	0.70	14	15 and 890	−5.7 (−12.9 with BV)	∼ −5–20	²⁷
NIR-GECO1	678/704	12	1.0	5.1, 4.9	100 ⁽²⁾	134 ⁽²⁾	2.4 ⁽⁶⁾	20 ⁽⁶⁾	8×	0.99	1.5 ⁽⁶⁾	4.0 ⁽⁶⁾	215 885	∼ −4.5 (∼ −10 with BV ⁽⁶⁾)	n.a.	²⁶
NIR-GECO2G	678/704	13	1.3	5.3, 4.8	n.a.	∼130 ⁽⁵⁾	∼5 ⁽⁵⁾	n.a.	n.a.	0.78	∼1.2	∼3	480	∼ −16	n.a.	²⁵
NIR-GECO2	678/704	12	0.75	5.3, 4.8	n.a.	∼130 ⁽⁵⁾	∼2 ⁽⁵⁾	n.a.	n.a.	0.94	∼1.3	∼3.5	331	∼ −17	n.a.	²⁵
FR-GECO1a	596/642	3.2	27	8.9, 8.0	n.a.	n.a.	n.a.	n.a.	6×	1.5	0.008	0.3	29	∼ 10	n.a.	²⁸
FR-GECO1c	596/646	1.1	28	9.5, 7.9	n.a.	n.a.	n.a.	n.a.	18×	2.0	0.001	0.16	83	∼ 33	n.a.	²⁸
HaloCaMP1a	640–642/653–655	n.a.	223	n.a.	n.a.	n.a.	n.a.	n.a.	5×	n.a.	n.a.	n.a.	190	2	n.a.	²³
HaloCaMP1b	640–642/653–655	n.a.	134	n.a.	n.a.	n.a.	n.a.	n.a.	9×	n.a.	n.a.	n.a.	43	8	n.a.	²³
GCaM6s	497/515	∼5	123	9.8, 6.0	n.a.	n.a.	n.a.	n.a.	60×	2.9	0.48	1.8	144	28	23	³²

⁽¹⁾

Molecular brightness is determined by extinction coefficient multiplied by quantum yield.

⁽²⁾

Determined in²⁷, using 605/30 nm excitation and 647 nm longpass emission filters at 14 mW/cm2 light power density at the back aperture of the lens, and normalized to absorption efficiency of the biosensors at 605 nm.

⁽³⁾

Determined in transiently transfected live HeLa cells. Effective (a.k.a. cellular) brightness of iGECI with 25 μM of exogenous BV was assumed to be 100%.

⁽⁴⁾

Determined for 1–10 electrical pulses in cultured neurons, without adding exogenous BV.

⁽⁵⁾

Estimated based on data in ²⁷ and ²⁵.

⁽⁶⁾

Measured in ²⁷. Other NIR-GECO1 data are from ²⁶.

n.a., not available