Electro-optic response of second-harmonic generation membrane potential sensors

Area of Science:

• Biophysics
• Molecular Photonics
• Membrane Biophysics

Background:

• Amphiphilic push-pull chromophores are crucial for sensing membrane potential.
• Second-harmonic generation (SHG) microscopy offers high spatial resolution for biological imaging.
• Understanding chromophore response to electric fields is key for sensor development.

Purpose of the Study:

• To quantify and characterize the second-harmonic generation (SHG) response of amphiphilic push-pull chromophores under a transmembrane electric field.
• To develop a method for estimating photoinduced charge shifts in chromophores.
• To provide insights for optimizing membrane potential sensors used in SHG microscopy.

Main Methods:

• Utilized giant unilamellar vesicles (GUVs) labeled with amphiphilic push-pull chromophores.
• Applied an alternating electric field across the GUVs.
• Analyzed the dispersion of the chromophore's field response.

Main Results:

• Quantified the SHG response of chromophores to transmembrane electric fields.
• Demonstrated that the technique can estimate photoinduced charge shifts for purely electro-optic responses.
• Results align with predictions from two-level perturbation theory.

Conclusions:

• The developed technique accurately quantifies chromophore response to electric fields.
• This work provides a foundation for designing more sensitive and accurate membrane potential sensors.
• The findings are directly applicable to advancing SHG microscopy for biological applications.