Amantadine partition and localization in phospholipid membrane: a solution NMR study

Area of Science:

• Biochemistry
• Biophysics
• Pharmacology

Background:

• Quantifying drug partitioning into lipid bilayers is crucial for pharmaceutical development.
• Understanding drug-membrane interactions informs drug delivery and efficacy.
• Existing methods may lack precision or broad applicability.

Purpose of the Study:

• To develop and validate a novel method for accurately measuring the membrane partition coefficient (K(p)) of drug compounds.
• To investigate the membrane partition potential of amantadine in phospholipid bilayers.
• To elucidate the role of electrostatic interactions in drug-membrane binding.

Main Methods:

• Utilized liquid-state Nuclear Magnetic Resonance (NMR) diffusion measurements.
• Employed fast-tumbling lipid/detergent bicelles for model membrane systems.
• Incorporated Saturation Transfer Difference (STD) NMR experiments.

Main Results:

• Amantadine exhibits a high partition coefficient (K(p)) in DMPC (27.6) and POPC (37.8) lipid bilayers.
• Introduction of negatively charged POPG lipids significantly increased amantadine's K(p), highlighting electrostatic effects.
• STD NMR indicated amantadine localizes near the phosphate headgroup and hydrocarbon core of the lipid bilayer.

Conclusions:

• The combined NMR diffusion and bicelle approach accurately quantifies drug membrane partition potential.
• Amantadine possesses significant membrane affinity, influenced by both hydrophobic and electrostatic interactions.
• This methodology is broadly applicable for characterizing small molecule interactions with phospholipid membranes.