Electrostatic interactions of fluorescent molecules with dielectric interfaces studied by total internal reflection...

Area of Science:

• Physical Chemistry
• Biophysics
• Surface Science

Background:

• Understanding fluorophore behavior at interfaces is critical for advanced microscopy techniques.
• Electrostatic interactions significantly influence molecular dynamics near surfaces.
• Objective-based Total Internal Reflection Fluorescence Correlation Spectroscopy (TIR-FCS) offers a powerful tool for probing these interactions.

Purpose of the Study:

• To investigate electrostatic interactions between dielectric surfaces and various charged fluorophores.
• To analyze the influence of ionic strength on these interfacial dynamics.
• To correlate electrostatic effects with fluorescence properties like triplet-state dynamics.

Main Methods:

• Utilized objective-based Total Internal Reflection Fluorescence Correlation Spectroscopy (TIR-FCS).
• Monitored interfacial dynamics of cationic, anionic/dianionic, zwitterionic, and neutral fluorophores (rhodamine 123, rhodamine 6G, fluorescein, rhodamine 110, ATTO 488).
• Varied ionic strength at physiological pH and analyzed autocorrelation functions and triplet-state parameters.

Main Results:

• Fluorophores exhibited electrostatic attraction or repulsion at the glass surface based on their net charge.
• Ionic strength modulated the amplitude and time-evolution of the autocorrelation function.
• Triplet-state population and relaxation times were affected by electrostatic interactions, influencing count-rate-per-molecule.

Conclusions:

• Electrostatic interactions significantly influence fluorophore behavior at dielectric surfaces.
• TIR-FCS provides detailed insights into surface-bound molecular dynamics and electrostatic forces.
• This approach offers a promising method for characterizing interfacial electrostatic phenomena in complex environments.