Archon2

Sibling variant of Archon1 with superior membrane localization and brightness at the cost of reduced sensitivity.

Category: Opsin GEVI
Published: 2018-02-26 — Nature Chemical Biology 2018
Derived from: QuasAr2
Response polarity: positive-going (fluorescence increases on depolarization)
Spectrum: excitation peak 586 nm, emission peak 693 nm (Archon2)
Plasmid: Addgene #108421
Tags: Archaerhodopsin, Red, Near-infrared

Headline values (as shown in the GEVIBench table)

Metric	Value	Definition
Brightness (B/B_EGFP)	0.0067× 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)	2.0 / 0.72 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	+20%	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	18% (median of 2 measurements: 13.7%)	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)	2.4 ms	Full width at half maximum of the optical spike waveform.
Photostability t75% @ 100 mW/mm²	1.2 h	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 2.05 ms, τ_off 0.72 ms at 32°C — Piatkevich 2018, Table S1

ΔF/F per 100 mV

+20%, 1P — Piatkevich 2018, Fig. 1g

ΔF/F per action potential

18%, 1P — Piatkevich 2018, Table S1
9.4%, 1P — Piatkevich 2018, Table S2

AP width (FWHM)

2.4 ms at 2300 Hz sampling, Mouse, cultured hippocampal neurons, in vitro, 1P — Piatkevich 2018, Fig. S16e

Brightness comparisons

8.01× the brightness of QuasAr2 — Piatkevich 2018, Fig. 2b

Photobleaching

t75% = 534 s at 800 mW/mm², 1P — Piatkevich 2018, Fig. 2i

Fluorescence–voltage (F–V) curve

ΔF/F (%) at each membrane potential, normalized to 0 at −70 mV: -100 mV: -7%; -80 mV: -2%; -70 mV: 0%; -60 mV: 2%; -40 mV: 6%; -20 mV: 10%; 0 mV: 13%; 20 mV: 17%; 40 mV: 20%; 60 mV: 23% — Piatkevich 2018, Fig. S16c

Research papers using Archon2 (4)

A robotic multidimensional directed evolution approach applied to fluorescent voltage reporters — Piatkevich KD, Jung EE, Straub C, Linghu C, Park D, Suk HJ, Hochbaum DR, Goodwin D, Pnevmatikakis E, Pak N, Kawashima T, Yang CT, Rhoades JL, Shemesh O, Asano S, Yoon YG, Freifeld L, Saulnier JL, Riegler C, Engert F, Hughes T, Drobizhev M, Szabo B, Ahrens MB, Bhatt DH, Schreiter ER, Sabatini BL, Bhatt DH, Boyden ES, Nature Chemical Biology 2018 (HEK293T cells, in vitro; Mouse cortex, acute brain slices; Cultured neurons, in vitro)
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, Bhatt DH, Verkhusha VV, Knöpfel T, ACS Chemical Neuroscience 2020 (HEK293T cells, in vitro; Cultured hippocampal neurons, in vitro)
Absorption and Emission Spectroscopic Investigation of the Thermal Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor Archon2 — Penzkofer A, Silapetere A, Hegemann P, International Journal of Molecular Sciences 2020 (Purified protein in Tris buffer, in vitro spectroscopy)
Photocycle dynamics of the Archaerhodopsin 3 based fluorescent voltage sensor Archon2 — Penzkofer A, Silapetere A, Hegemann P, Journal of Photochemistry and Photobiology B: Biology 2021 (Purified protein in Tris buffer, in vitro spectroscopy)

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.