Photocycle dynamics of the Archaerhodopsin 3 based fluorescent voltage sensor Archon2

Penzkofer, Alfons; Silapetere, Arita; Hegemann, Peter

doi:10.1016/j.jphotobiol.2021.112331

Cited by 10 publications

(8 citation statements)

References 67 publications

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“…These TSs must be considered approximate as it has not been possible to carry out a geometry optimization starting from a computed Hessian matrix as well as to compute a Hessian matrix at the end of the TS search. Furthermore, despite the increased FQY of the investigated Arch variants, recent measurements of the excited state lifetime (ESL) of some of the variants were found to be in the time range of picoseconds 30 , 31 . For this reason, we don’t account in our calculation for T 1 /S 1 intersystem crossing (ISC) as a viable competitive process to S 1 emission also considering that T 1 is a π-π* state with orbitals parallel (non-orthogonal) to those characterizing the S 1 state.…”

Section: Resultsmentioning

confidence: 89%

On the fluorescence enhancement of arch neuronal optogenetic reporters

et al. 2022

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The lack of a theory capable of connecting the amino acid sequence of a light-absorbing protein with its fluorescence brightness is hampering the development of tools for understanding neuronal communications. Here we demonstrate that a theory can be established by constructing quantum chemical models of a set of Archaerhodopsin reporters in their electronically excited state. We found that the experimentally observed increase in fluorescence quantum yield is proportional to the computed decrease in energy difference between the fluorescent state and a nearby photoisomerization channel leading to an exotic diradical of the protein chromophore. This finding will ultimately support the development of technologies for searching novel fluorescent rhodopsin variants and unveil electrostatic changes that make light emission brighter and brighter.

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Section: Resultsmentioning

confidence: 89%

On the fluorescence enhancement of arch neuronal optogenetic reporters

et al. 2022

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“…The resulting photoproduct would maintain similar chromophore geometry and charge distribution and would be almost spectroscopically indistinguishable from the IDS. Detailed studies of absorption spectra changes of QuasAr1 23 and Archon1 45 upon illumination support the proposed heterogeneity of the protonated species.…”

Section: Discussionmentioning

confidence: 62%

QuasAr Odyssey: the origin of fluorescence and its voltage sensitivity in microbial rhodopsins

et al. 2022

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Rhodopsins had long been considered non-fluorescent until a peculiar voltage-sensitive fluorescence was reported for archaerhodopsin-3 (Arch3) derivatives. These proteins named QuasArs have been used for imaging membrane voltage changes in cell cultures and small animals, but they could not be applied in living rodents. To develop the next generation of sensors, it is indispensable to first understand the molecular basis of the fluorescence and its modulation by the membrane voltage. Based on spectroscopic studies of fluorescent Arch3 derivatives, we propose a unique photo-reaction scheme with extended excited-state lifetimes and inefficient photoisomerization. Molecular dynamics simulations of Arch3, of the Arch3 fluorescent derivative Archon1, and of several its mutants have revealed different voltage-dependent changes of the hydrogen-bonding networks including the protonated retinal Schiff-base and adjacent residues. Experimental observations suggest that under negative voltage, these changes modulate retinal Schiff base deprotonation and promote a decrease in the populations of fluorescent species. Finally, we identified molecular constraints that further improve fluorescence quantum yield and voltage sensitivity.

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“…Information on the photocycles from a variety of mutants can lead to optimization of the illumination conditions to accumulate bright and voltage sensitive intermediates for better SNR in 1P and 2P imaging. 130,153 Single mutations are typically created to positively influence one emergent property of the GEVI protein (brightness, sensitivity, response kinetics, photocurrent) but usually also affect other aspects of GEVI functionality. For example, the counterion is typically the first engineering site to block the proton transfer pathway and eliminate the photocurrent; however mutating the counterion alone often comes at the expense of voltage sensitivity or response kinetics.…”

Section: Discussionmentioning

confidence: 99%

Voltage imaging with engineered proton-pumping Rhodopsins: Insights from the proton transfer pathway

Meng

Ganapathy

Roemburg

et al. 2023

Preprint

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Voltage imaging using genetically encoded voltage indicators (GEVI) has taken the field of neuroscience by storm in the past decade. Its ability to create subcellular and network level readouts of electrical dynamics depends critically on the kinetics of the response to voltage of the indicator used. Engineered Microbial Rhodopsins form a GEVI sub-class known for their high voltage sensitivity and fast response kinetics. Here we review the essential aspects of mi-crobial rhodopsin photocycles that are critical to understanding the mechanisms of voltage sensitivity in these pro-teins and link them to insights from efforts to create faster, brighter and more sensitive Microbial Rhodopsin-based GEVIs.

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Photocycle dynamics of the Archaerhodopsin 3 based fluorescent voltage sensor Archon2

Cited by 10 publications

References 67 publications

On the fluorescence enhancement of arch neuronal optogenetic reporters

On the fluorescence enhancement of arch neuronal optogenetic reporters

QuasAr Odyssey: the origin of fluorescence and its voltage sensitivity in microbial rhodopsins

Voltage imaging with engineered proton-pumping Rhodopsins: Insights from the proton transfer pathway

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