GEVIBench › All sensors › VARNAM
VARNAM
Voltage indicator using opsin-FRET architecture with red fluorescent protein for improved tissue penetration.
- Category: eFRET GEVI
- Published: 2018-11-12 — Nature Methods 2018
- Derived from: Ace2N-mNeon
- Response polarity: negative-going (fluorescence decreases on depolarization)
- Spectrum: excitation peak 558 nm, emission peak 592 nm (VARNAM)
- Plasmid: Addgene #115554
- Tags: Ace opsin, mRuby3, Red, FRET
Headline values (as shown in the GEVIBench table)
| Metric | Value | Definition |
|---|---|---|
| Brightness (B/B_EGFP) | 0.85× 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) | 3.0 / 2.8 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 | -10.8% (median of 3 measurements: −13.5%) | 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 | 0.1% | 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 | 4.8% (median of 3 measurements: 5.3%) | 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) | 3.6 ms | Full width at half maximum of the optical spike waveform. |
| Photostability t75% @ 100 mW/mm² | 30 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) | 7 | 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 3.04 ms, τ_off 2.75 ms at 22-25°C — Kannan 2018, Table S1
ΔF/F per 100 mV
- -10.8%, 1P — Liu 2021, Fig. 2c
- -13.5%, 1P — Kannan 2018, Fig. 2b
- -17.9%, 1P — Han 2023, Fig. 1B
ΔF/F per mV (subthreshold)
- 0.104%/mV — Abdelfattah 2023, Fig. S5E
ΔF/F per action potential
- 4.8%, 1P — Kannan 2018, Fig. 3d
- 5.3%, 1P — Liu 2021, Fig. 3a
- 8.4%, 1P — Kannan 2018, Fig. 2f
AP width (FWHM)
- 3.6 ms at 500 Hz sampling, Drosophila, PPL1-α'2α2 dopaminergic neuron, in vivo, 1P, 25°C — Kannan 2018, Fig. 6d
Brightness comparisons
- 2286× the brightness of Arch — Monakhov 2020, Table 1
- 0.71× the brightness of Ace2N-mNeon — Kannan 2018, Fig. 1j
- 0.6× the brightness of Cepheid1b — Han 2023, Fig. S5
- 2.32× the brightness of Cepheid1s — Han 2023, Fig. S5
- 1× the brightness of VARNAM2 — Kannan 2022, Fig. S11A
Photobleaching
- t75% = 164 s at 15.9 mW/mm², 1P — Han 2023, Fig. S6A
- t50% = 368 s, 1P — Kannan 2022, Fig. S11B
- t75% = 70 s at 48 mW/mm², 1P — Liu 2021, Ext. Fig. 4g
- t75% = 66 s at 15 mW/mm², 1P — Kannan 2018, Fig. S7a
Fluorescence–voltage (F–V) curve
ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -150 mV: 9%; -130 mV: 8%; -110 mV: 6.5%; -90 mV: 3.5%; -70 mV: 0%; -50 mV: -4%; -30 mV: -7.5%; -10 mV: -10.5%; 10 mV: -12.5%; 30 mV: -13.5%; 50 mV: -14% — Kannan 2018, Fig. 2b
Research papers using VARNAM (7)
- Fast, in vivo voltage imaging using a red fluorescent indicator — Kannan M, Vasan G, Huang C, Haziza S, Li JZ, Inan H, Schnitzer MJ, Pieribone VA, Nature Methods 2018 (HEK cells, cultured neurons, mouse cortex and hippocampus in vivo, Drosophila in vivo)
- A high-speed, bright, red fluorescent voltage sensor to detect neural activity — Beck C, Gong Y, Scientific Reports 2019 (HEK293T cells, cultured neurons)
- Screening and Cellular Characterization of Genetically Encoded Voltage Indicators Based on Near-Infrared Fluorescent Proteins — Monakhov MV, Matlashov ME, Colavita M, Song C, Shcherbakova DM, Antic SD, Verkhusha VV, Knopfel T, ACS Chemical Neuroscience 2020 (HEK cells, cultured neurons)
- A far-red hybrid voltage indicator enabled by bioorthogonal engineering of rhodopsin on live neurons — Liu S, Lin C, Xu Y, Luo H, Peng L, Zeng X, Zheng H, Chen PR, Zou P, Nature Chemistry 2021 (Rat hippocampal neurons, cultured)
- 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 (Mouse visual cortex and hippocampus in vivo, Drosophila in vivo)
- Sensitivity optimization of a rhodopsin-based fluorescent voltage indicator — Abdelfattah AS, et al., Neuron 2023 (HEK293 cells, cultured neurons)
- Bright and sensitive red voltage indicators for imaging action potentials in brain slices and pancreatic islets — Han Y, Yang J, Li Y, Chen Y, Ren H, Ding R, Qian W, Ren K, Xie B, Deng M, Xiao Y, Chu J, Zou P, Science Advances 2023 (HEK293T cells, in vitro; rat hippocampal neurons, 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.