Charge shift optical probes of membrane potential. Theory

Area of Science:

• Computational Chemistry
• Biophysical Chemistry
• Molecular Probes

Background:

• Membrane potential probes are crucial for understanding cellular function.
• Existing probes have limitations in sensitivity and orientation.
• Electrochromism offers a potential mechanism for improved probe performance.

Purpose of the Study:

• To investigate the electrochromic properties of membrane potential probes using molecular orbital calculations.
• To characterize charge distribution and electron density shifts in chromophores.
• To predict and rationalize the electrochromic response magnitude.

Main Methods:

• Molecular orbital calculations were performed on known and novel chromophores.
• Analysis of charge distribution and excitation-induced electron density shifts.
• Comparison of computational predictions with rigorous calculations and experimental data.

Main Results:

• Computational predictions of electrochromic response magnitude were consistent with experimental data.
• A novel charge-shift electrochromism mechanism was identified in ionic chromophores.
• Amphipathic structures were found to enhance probe orientation and responsiveness.

Conclusions:

• Molecular orbital calculations are effective for predicting electrochromic responses in membrane potential probes.
• Charge-shift electrochromism in amphipathic molecules presents a promising avenue for developing advanced probes.
• The 4-(p-aminostyryl) pyridinium cation is identified as a particularly promising charge-shift chromophore.