GEVIBench › All sensors › pAceR
pAceR
Reverse-polarity red variant of VARNAM2 that brightens upon depolarization, enabling dual-polarity multiplexed voltage imaging alongside negative-going sensors in the same color channel.
- Category: eFRET GEVI
- Published: 2022-11-04 — Science 2022
- Derived from: VARNAM2
- Response polarity: positive-going (fluorescence increases on depolarization)
- Spectrum: excitation peak 558 nm, emission peak 592 nm (pAceR)
- Plasmid: Addgene #195534
- Tags: Ace opsin, mRuby3, Red, FRET, Positive
Headline values (as shown in the GEVIBench table)
| Metric | Value | Definition |
|---|---|---|
| Brightness (B/B_EGFP) | 0.59× 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) | 3.8 / 4.1 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 | +27.8% | 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 | 0.2% (estimated from the F–V curve) | 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 | 3.2% (median of 2 measurements: 4.9%) | 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) | 2.7 ms | Full width at half maximum of the optical spike waveform. |
| Photostability t75% @ 100 mW/mm² | 41 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) | 2 | 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 3.78 ms, τ_off 4.13 ms at 22°C — Kannan 2022, Table S1
ΔF/F per 100 mV
- +27.8%, 1P — Kannan 2022, Table S1
ΔF/F per action potential
- 3.2%, 1P — Kannan 2022, Fig. 1I
- 6.6%, 1P — Liu 2025, Table S2
AP width (FWHM)
- 2.7 ms at 400 Hz sampling, Mouse, V1 VIP+ interneurons, awake, in vivo, 1P, 37°C — Kannan 2022, Fig. 1I
Brightness comparisons
- 0.7× the brightness of VARNAM2 — Kannan 2022, Fig. S11A
Photobleaching
- t75% = 162 s, 1P — Kannan 2022, Fig. S11B
Fluorescence–voltage (F–V) curve
ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -150 mV: -18%; -130 mV: -15%; -110 mV: -10%; -90 mV: -5%; -70 mV: 0%; -50 mV: 3%; -30 mV: 7%; -10 mV: 14%; 10 mV: 20%; 30 mV: 28%; 50 mV: 33% — Kannan 2022, Fig. 1D
Research papers using pAceR (2)
- Dual-polarity voltage imaging of the concurrent dynamics of multiple neuron types — Kannan M, Vasan G, Haziza S, Huang C, Chrapkiewicz R, Luo J, Cardin JA, Schnitzer MJ, Pieribone VA, Science 2022 (HEK cells, in vitro; mouse hippocampus CA1, in vivo; Drosophila PPL1 dopaminergic neurons, in vivo)
- Positive-going hybrid indicators for voltage imaging in excitable cells and tissues — Liu S, et al., Science Advances 2025 (Cultured rat hippocampal neurons; pAceR measured (6.6 ± 0.5% ΔF/F0 per AP, n=5, Table S2) as a positive-going reference, 1P epifluorescence)
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.