PMID-22308458 Optically monitoring voltage in neurons by photo-induced electron transfer through molecular wires.
- Photoinduced electron transfer.
- About what you would think -- a photon bumps an electron into a higher orbital, and this electron can be donated to another group or drop back down & fluoresce a photon.
- Good sensitivity: of 20-27% per 100mV, fast kinetics.
- Not presently genetically targetable.
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- Makes sense in terms of energy: "A 100-mV depolarization changes the PeT driving force by 0.05 eV (one electron × half of 100-mV potential, or 0.05 V). Because PeT is a thermally controlled process, the value of 0.05 eV is large relative to the value of kT at 300 K (0.026 eV), yielding a large dynamic range between the rates of PeT at resting and depolarized potentials.
- Why electrochromic dyes have plateaued:
- "In contrast, electrochromic dyes have smaller delta G values, 0.003 (46) to 0.02 (47) eV, and larger comparison energies. Because the interaction is a photochemically controlled process, the energy of the exciting photon is the comparison energy, which is 1.5–2 eV for dyes in the blue-to-green region of the spectrum. Therefore, PeT and FRET dyes have large changes in energy versus their comparison energy (0.05 eV vs. 0.026 eV), giving high sensitivities; electrochromic dyes have small changes compared with the excitation photon (0.003–0.02 eV vs. 2 eV), producing low voltage sensitivity."
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