PROPS

First microbial opsin-based voltage indicator, though only functional in bacteria and extremely dim.

Category: Opsin GEVI
Published: 2011-07-15 — Science 2011
Response polarity: positive-going (fluorescence increases on depolarization)
Spectrum: excitation peak 555 nm, emission peak 710 nm (PROPS)
Plasmid: Addgene #33780
Tags: NIR FP, Microbial, Bacteria-only

Headline values (as shown in the GEVIBench table)

Metric	Value	Definition
Brightness (B/B_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)	4.7 / 4.7 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	+150%	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	0.8% (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)	4	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 4.7 ms, τ_off 4.7 ms at 25°C — Kralj 2011, Fig. 1D

ΔF/F per 100 mV

+150%, 1P — Kralj 2011, Fig. 1C

Fluorescence–voltage (F–V) curve

ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -150 mV: -47%; -130 mV: -41%; -110 mV: -29%; -90 mV: -13%; -70 mV: 0%; -50 mV: 19%; -30 mV: 42%; -10 mV: 55%; 10 mV: 75%; 30 mV: 91%; 50 mV: 100%; 70 mV: 112% — Kralj 2011, Fig. 1C

Research papers using PROPS (4)

Electrical spiking in Escherichia coli probed with a fluorescent voltage-indicating protein — Kralj JM, Hochbaum DR, Douglass AD, Cohen AE, Science 2011 (E. coli (BW25113 and other strains), in vitro)
Initial photophysical characterization of the proteorhodopsin optical proton sensor (PROPS) — Nadeau JL, Frontiers in Neuroscience 2015 (E. coli, in vitro)
Voltage-gated calcium flux mediates Escherichia coli mechanosensation — Bruni GN, Weekley RA, Dodd BJT, Kralj JM, Proceedings of the National Academy of Sciences 2017 (E. coli, in vitro)
Membrane voltage dysregulation driven by metabolic dysfunction underlies bactericidal activity of aminoglycosides — Bruni GN, Kralj JM, eLife 2020 (E. coli, 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.