Dibucaine interaction with phospholipid vesicles. A resonance energy-transfer study

Area of Science:

• Biophysics
• Membrane Biophysics
• Pharmacology

Background:

• Local anesthetics like dibucaine are crucial for pain management.
• Understanding drug-membrane interactions is key to drug design and delivery.
• Model membrane systems provide insights into complex biological environments.

Purpose of the Study:

• To determine the precise location of dibucaine within a phospholipid bilayer.
• To investigate the effect of membrane phase transitions on dibucaine localization.
• To elucidate the photophysical properties and membrane partitioning of dibucaine.

Main Methods:

• Resonance energy transfer (RET) between dibucaine (donor) and fluorescently labeled lipid probes (acceptors).
• Utilizing small unilamellar vesicles (SUVs) of dipalmitoylglycerophosphocholine (DPPC) as a model membrane.
• Measuring dibucaine fluorescence lifetime and partition coefficients.

Main Results:

• Efficient RET was observed with a critical radius (Ro) of 2.1 nm, indicating close proximity between dibucaine and probes.
• Dibucaine was localized near the glycerol backbone of DPPC lipids.
• Dibucaine's membrane location was unaffected by the gel-to-liquid-crystal phase transition of DPPC.
• The charged form of dibucaine is the predominant species within the membrane.

Conclusions:

• Dibucaine preferentially partitions into the lipid headgroup region of the membrane.
• Membrane fluidity does not significantly alter dibucaine's intercalation site.
• Intramolecular charge-transfer contributes to the photophysics of dibucaine.