Charge- and pH-dependent binding sites for dibucaine in ionic micelles: a fluorescence study

Area of Science:

• Pharmacology
• Physical Chemistry
• Biophysics

Background:

• Local anesthetics like dibucaine interact with cell membranes.
• Understanding drug-membrane interactions is crucial for pharmacology.
• Micelles serve as models for cell membranes.

Purpose of the Study:

• To investigate the binding of dibucaine to micelles of varying detergent charges.
• To determine how micelle charge affects dibucaine's pKa and binding affinity.
• To estimate electrostatic potentials at the micelle surface and assess non-coulombic interactions.

Main Methods:

• Fluorescence spectroscopy of dibucaine to measure pKa shifts and binding constants.
• Utilizing cationic, zwitterionic, and anionic detergent micelles.
• Fluorescence quenching with sodium iodide and nitroxide stearic acid derivatives for depth profiling.

Main Results:

• Dibucaine binding is largely independent of micelle charge for its neutral form.
• pKa shifts indicate electrostatic potentials influencing dibucaine's charged form.
• Discrepancies in cationic micelles suggest the importance of non-coulombic interactions.

Conclusions:

• Dibucaine's binding behavior is complex and influenced by micelle electrostatic properties.
• Non-coulombic interactions play a significant role in drug-membrane interactions.
• This study provides insights into the electrostatic environment of drug binding sites.