ASAP1

First ASAP sensor, establishing the VSD/cpGFP architecture for fast, negative-going fluorescence responses to voltage.

Category: VSD-cpGFP GEVI
Published: 2014-04-22 — Nature Neuroscience 2014
Response polarity: negative-going (fluorescence decreases on depolarization)
Spectrum: excitation peak 490 nm, emission peak 510 nm (ASAP1)
Two-photon compatible: yes
Plasmid: Addgene #52519
Tags: cpGFP

Headline values (as shown in the GEVIBench table)

Metric	Value	Definition
Brightness (B/B_EGFP)	0.43× EGFP	Molecular brightness relative to EGFP (extinction coefficient × quantum yield, or a measured ratio). Sensors not measured against EGFP directly are placed through a chain of pairwise brightness comparisons, combined by geometric mean.
Kinetics τ_on / τ_off (ms)	6.7 / 12 ms	Activation / decay time constants in ms (amplitude-weighted mean τ for multi-exponential fits). The value shown averages the measurements made at physiological temperature (≥33 °C); if there are none, it is the measurement closest to 33 °C.
ΔF/F per 100 mV	-17.5% (median of 4 measurements: −24.5%)	Steady-state fluorescence change for a 100 mV depolarization step (−70 → +30 mV); the sign gives the polarity. The table shows the first listed measurement; the median across measurements (one-photon preferred) is used for sorting.
ΔF/F per mV	0.21%	Subthreshold sensitivity: fluorescence change per mV near rest (−90 to −50 mV). Where no value is reported directly, it is estimated from the F–V curve.
ΔF/F per AP	6.3% (median of 4 measurements: 7.45%)	Fluorescence change per single action potential in neurons. The table shows the first listed measurement; the median across measurements (one-photon preferred) is used for sorting.
AP width (FWHM, ms)	6.2 ms	Full width at half maximum of the optical spike waveform.
Photostability t75% @ 100 mW/mm²	11 s	Time for fluorescence to fall to 75% of its initial value under one-photon illumination, linearly dose-scaled to 100 mW/mm² (t50% is used where the 75% crossing falls inside a fast initial transient). Two-photon curves are not dose-scaled and are excluded.
Papers using it (N_used)	21	Number of published research papers, tracked by GEVIBench, that used the sensor for an experiment (a popularity / track-record measure).

Measurements and sources

Kinetics

τ_on 29.7 ms, τ_off 29.5 ms at 22°C — St-Pierre 2014, Fig. 1e
τ_on 44 ms, τ_off 66.9 ms at 22°C — Chamberland 2017, Table 1
τ_on 6.7 ms, τ_off 11.6 ms at 23°C — Zou 2014, Table 1
τ_on 23.3 ms, τ_off 36.4 ms at 23°C — Villette 2019, Table S1

ΔF/F per 100 mV

-17.5%, 1P — St-Pierre 2014, Fig. 1d
-23.3%, 1P — Chamberland 2017, Fig. 1C
-25.7%, 1P — Milosevic 2020, Fig. 2D
-28.8%, 1P — Zou 2014, Table 1

ΔF/F per mV (subthreshold)

0.21%/mV, 1P (Subthreshold voltage sensitivity ≈ 0.21 %/mV, derived from the Fig. 3b (top) quantification in voltage-clamped cultured rat hippocampal neurons: ASAP1 peak −ΔF/F was 1.20 / 2.05 / 2.85 / 4.52% for simulated subthreshold depolarization waveforms of 5 / 10 / 15 / 20 mV peak amplitude (17 ms peak FWHM, n = 6 neurons, 1P widefield, 22°C). Through-origin least squares over the four points gives 0.213 %/mV (free-intercept fit gives 0.215 %/mV with a ~0 intercept, i.e. the response is linear over this range). Read off the bar graph, so ±~5%. Comparable steady-state chord slope from the HEK293A F−V curve (Fig. 1d, −80 → −60 mV) is 0.31 %/mV; the neuronal waveform value is lower because these are brief transient responses, not steady-state steps. Cross-GEVI: ArcLight Q239 in the same panel gives ≈ 0.13 %/mV (0.80 / 1.63 / 2.12 / 2.28%).) — St-Pierre 2014, Fig. 3b

ΔF/F per action potential

6.3%, 1P — St-Pierre 2014, Fig. 4a
8.6%, 1P — Chamberland 2017, Fig. 2I
2.8%, 1P — Lee 2017, Table 3
17.8%, 1P — Zou 2014, Table 1

AP width (FWHM)

3.7 ms at 827 Hz sampling, Rat cultured hippocampal neurons, current-triggered single AP, in vitro, 1P, 22°C — St-Pierre 2014, Fig. 1f
3.8 ms at 3700 Hz sampling, Organotypic hippocampal slice cultures, current-triggered single AP, two-photon RAMP (FEVIR), 2P, 22°C — Chamberland 2017, Fig. 6E
9 ms at 1000 Hz sampling, Rat, cultured hippocampal neurons, in vitro, 1P — Chamberland 2017, Fig. 2J
8.5 ms at 500 Hz sampling, Mouse, cultured primary cortical/hippocampal neurons (P0.5), in vitro, 1P — Milosevic 2020, Fig. 1A

Brightness comparisons

1× the brightness of ASAP2s — Chamberland 2017, Fig. S2
0.61× the brightness of ArcLight — Milosevic 2020, Fig. 2F
0.94× the brightness of ASAP3 — Nair 2025, Fig. 2C

Photobleaching

t75% = 508 s at 0.12 mW/mm², 1P — St-Pierre 2014, Fig. S9
t75% = 52 s at 11 mW/mm², 1P — Chamberland 2017, Fig. 1—figure supplement 3A
t75% = 16 s at 100 mW/mm², 1P — Abdelfattah 2016, Fig. 3I
t50% = 0.84 s at ~1 mW (950 nm, 2P point scan), 2P — Abdelfattah 2016, Fig. 4C

Fluorescence–voltage (F–V) curve

ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -120 mV: 23.4%; -100 mV: 11.7%; -80 mV: 3.3%; -70 mV: 0%; -60 mV: -2.8%; -40 mV: -6.7%; -20 mV: -9.8%; 0 mV: -12.8%; 30 mV: -17.5%; 50 mV: -21.1% — St-Pierre 2014, Fig. 1d

Research papers using ASAP1 (21)

High-fidelity optical reporting of neuronal electrical activity with an ultrafast fluorescent voltage sensor — St-Pierre F, Marshall JD, Yang Y, Gong Y, Schnitzer MJ, Lin MZ, Nature Neuroscience 2014 (HEK293A cells; rat hippocampal neurons, in vitro)
A Bright and Fast Red Fluorescent Protein Voltage Indicator That Reports Neuronal Activity in Organotypic Brain Slices — Abdelfattah AS, Farhi SL, Zhao Y, Brinks D, Zou P, Ruangkittisakul A, Platisa J, Pieribone VA, Ballanyi K, Cohen AE, Campbell RE, Journal of Neuroscience 2016 (HEK293 cells; rat hippocampal neurons, in vitro)
Biophysical Characterization of Genetically Encoded Voltage Sensor ASAP1: Dynamic Range Improvement — Lee EEL, Bezanilla F, Biophysical Journal 2017 (Xenopus laevis oocytes; rat dorsal root ganglion neurons, in vitro)
Fast two-photon imaging of subcellular voltage dynamics in neuronal tissue with genetically encoded indicators — Chamberland S, et al., eLife 2017 (HEK293A cells; mouse hippocampal neurons, in vitro)
In Vitro Testing of Voltage Indicators: Archon1, ArcLightD, ASAP1, ASAP2s, ASAP3b, Bongwoori-Pos6, BeRST1, FlicR1, and Chi-VSFP-Butterfly — Milosevic MM, et al., eNeuro 2020 (HEK293 cells; mouse brain slices, in vitro)
Comparative Evaluation of Genetically Encoded Voltage Indicators — Bando Y, et al., Cell Reports 2019 (Mouse hippocampal neurons, in vitro)
Optical interrogation of neuronal circuitry in zebrafish using genetically encoded voltage indicators — Miyazawa H, et al., Scientific Reports 2018 (Zebrafish, cerebellum; spinal cord, in vivo)
Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors — Silic MR, Zhang G, Journal of Visualized Experiments 2018 (Zebrafish embryos; zebrafish tumors, in vivo)
Real-time detection of yeast membrane potential using ASAP1 voltage indicator — Limapichat W, et al., FEMS Yeast Research 2020 (Saccharomyces cerevisiae, in vitro)
In vivo wide-field voltage imaging in zebrafish with voltage-sensitive dye and genetically encoded voltage indicator — Hiyoshi K, et al., Development, Growth & Differentiation 2021 (Zebrafish larvae, cerebellum; spinal cord, in vivo)
Enabling comprehensive optogenetic studies of mouse hearts by simultaneous opto-electrical panoramic mapping and stimulation — Rieger M, et al., Nature Communications 2021 (Mouse heart, ex vivo)
In Vitro Matured Human Pluripotent Stem Cell-Derived Cardiomyocytes Form Grafts With Enhanced Structure and Function in Injured Hearts — Dhahri W, et al., Circulation 2022 (Human PSC-derived cardiomyocytes; rat heart, ex vivo)
Zebrafish Embryos Display Characteristic Bioelectric Signals during Early Development — Silic MR, et al., Cells 2022 (Zebrafish embryos, in vivo)
Optogenetic Reporters Delivered as mRNA Facilitate Repeatable Action Potential and Calcium Handling Assessment in Human iPSC-Derived Cardiomyocytes — Yiangou L, et al., Stem Cells 2022 (Human iPSC-derived cardiomyocytes, in vitro)
A fully-automated low-cost cardiac monolayer optical mapping robot — Lee P, et al., Frontiers in Cardiovascular Medicine 2023 (Human PSC-derived cardiomyocyte monolayers, in vitro)
Protocol for dual-optical mapping of voltage and calcium sensors in human pluripotent stem cell-derived cardiomyocytes — Alibhai FJ, et al., STAR Protocols 2025 (Human PSC-derived cardiomyocytes, in vitro)
Absolute Membrane Potential Recording with ASAP-Type Genetically Encoded Voltage Indicators Using Fluorescence Lifetime Imaging — Nair AG, et al., ACS Chemical Neuroscience 2025 (HEK293T cells, in vitro)
Bright and fast multicoloured voltage reporters via electrochromic FRET — Zou P, Zhao Y, Douglass AD, Hochbaum DR, Brinks D, Werley CA, Harrison DJ, Campbell RE, Cohen AE, Nature Communications 2014 (HEK293 cells; cultured rat hippocampal neurons, in vitro)
High-speed recording of neural spikes in awake mice and flies with a fluorescent voltage sensor — Gong Y, Huang C, Li JZ, Grewe BF, Zhang Y, Eismann S, Schnitzer MJ, Science 2015 (HEK293 cells; mouse cortex, in vivo; Drosophila, in vivo)
Ultrafast Two-Photon Imaging of a High-Gain Voltage Indicator in Awake Behaving Mice — Villette V, Chavarha M, Dimov IK, Bradley J, Pradhan L, Mathieu B, Evans SW, Chamberland S, Shi D, Yang R, Kim BB, Ayon A, Jalil A, St-Pierre F, Schnitzer MJ, Bi G, Toth K, Ding J, Dieudonné S, Lin MZ, Cell 2019 (HEK293A cells; mouse cortex and hippocampus, in vivo)
Improving a genetically encoded voltage indicator by modifying the cytoplasmic charge composition — Lee S, Geiller T, Jung A, Nakajima R, Song YK, Baker BJ, Scientific Reports 2017 (HEK293 cells, in vitro)

Data and citation

llms.txt — summary for language models
llms-full.txt — every sensor in full (Markdown)
gevis.json — all values and measurements with sources (JSON)
gevis.csv — one row per sensor (CSV)

Cite GEVIBench as: Adam E. Cohen and Daozheng Gong (2026). Voltage imaging: A practical guide. Neuron. https://doi.org/10.1016/j.neuron.2026.08.002

Generated from the GEVIBench database on 2026-10-12.