Electronic Preresonance Stimulated Raman Scattering Imaging of Red-Shifted Proteorhodopsins: Toward Quantitation of the Membrane Potential

J Phys Chem Lett. 2019 Aug 1;10(15):4374-4381. doi: 10.1021/acs.jpclett.9b01337. Epub 2019 Jul 22.

Abstract

Voltage imaging allows mapping of the membrane potential in living cells. Yet, current intensity-based imaging approaches are limited to relative membrane potential changes, missing important information conveyed by the absolute value of the membrane voltage. This challenge arises from various factors affecting the signal intensity, such as concentration, illumination intensity, and photobleaching. Here, we demonstrate electronic preresonance hyperspectral stimulated Raman scattering (EPR-hSRS) for spectroscopic detection of the membrane voltage using a near-infrared-absorbing microbial rhodopsin expressed in E. coli. This newly developed near-infrared active microbial rhodopsin enables electronic preresonance SRS imaging at high sensitivity. By spectral profiling, we identified voltage-sensitive SRS peaks in the fingerprint region in single E. coli cells. These spectral signatures offer a new approach for quantitation of the absolute membrane voltage in living cells.

MeSH terms

  • Escherichia coli / metabolism
  • Hydrogen-Ion Concentration
  • Infrared Rays
  • Membrane Potentials
  • Mutation
  • Rhodopsins, Microbial / chemistry*
  • Rhodopsins, Microbial / genetics
  • Rhodopsins, Microbial / metabolism
  • Single-Cell Analysis / methods
  • Spectrum Analysis, Raman / methods*

Substances

  • Rhodopsins, Microbial
  • proteorhodopsin