GEVIBench › All sensors › FlicR2
FlicR2
Directed-evolution variant of FlicR1 with roughly doubled voltage sensitivity, retaining the red cpmApple fluorescent reporter.
- Category: VSD-single FP
- Published: 2018-11-12 — Nature Methods 2018
- Derived from: FlicR1
- Response polarity: positive-going (fluorescence increases on depolarization)
- Spectrum: excitation peak 567 nm, emission peak 592 nm (FlicR2)
- Tags: cpmApple, Red, Positive-going
Headline values (as shown in the GEVIBench table)
| Metric | Value | Definition |
|---|---|---|
| Brightness (B/B_EGFP) | 0.50× 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) | 16 / 16 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 | +12.9% (median of 2 measurements: +12.9%) | 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 | 0.14% (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 | — | 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) | — | Full width at half maximum of the optical spike waveform. |
| Photostability t75% @ 100 mW/mm² | — | 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 16.2 ms, τ_off 15.8 ms at 22-25°C — Kannan 2018, Table S1
ΔF/F per 100 mV
- +12.9%, 1P — Kannan 2018, Fig. S2e
- +24%, 2P — Yang 2026, Fig. 2D
Brightness comparisons
- 0.18× the brightness of Ace2N-mNeon — Kannan 2018, Fig. 1j
- 1.1764705882352942× the brightness of VADER1 — Yang 2026, Fig. 2C
Fluorescence–voltage (F–V) curve
ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -120 mV: -5%; -100 mV: -5%; -70 mV: 0%; -50 mV: 2%; -40 mV: 4%; -20 mV: 11%; 0 mV: 20%; 30 mV: 24%; 50 mV: 27%; 70 mV: 27%; 90 mV: 25% — Yang 2026, Fig. 2D
Research papers using FlicR2 (2)
- 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, in vitro)
- A red-emitting, genetically encoded indicator for two-photon voltage recording in vivo — Yang S, McDonald AJ, Lu X, Villette V, Hakam N, Galdamez M, et al., bioRxiv 2026 (CHO cells, in vitro; HEK293A cells, in vitro; HEK-Kir2.1 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.