Membrane partition coefficients chromatographically measured using immobilized artificial membrane surfaces

Area of Science:

• Biochemistry
• Chromatography
• Pharmacokinetics

Background:

• Immobilized artificial membranes (IAMs) are chromatographic surfaces mimicking cell membranes.
• IAMs are prepared by covalently immobilizing cell membrane phospholipids.
• Solute partitioning into cell membranes is crucial for understanding drug behavior.

Purpose of the Study:

• To evaluate IAM chromatography as an in vitro method for predicting solute partitioning into cell membranes.
• To investigate the effect of lipid structure on drug binding to IAMs.
• To determine if solute binding to membranes is a bulk property.

Main Methods:

• IAM chromatography was used to measure solute capacity factors (k'IAM).
• Liposome partitioning was used to measure solute equilibrium partition coefficients (Km').
• IAMs were prepared using different phosphatidylcholine ligands to assess structural effects.

Main Results:

• Solute capacity factors (k'IAM) on IAM columns strongly correlated with solute partition coefficients (Km') in liposome systems (r = 0.907).
• IAM chromatography is experimentally more convenient than liposome systems for predicting membrane partitioning.
• Solute retention data were identical across IAMs with different phosphatidylcholine structures, indicating ligand structure is not critical.

Conclusions:

• IAM chromatography is a reliable and convenient in vitro method for predicting solute partitioning into cell membranes.
• The structure of the immobilized phosphatidylcholine ligand does not significantly affect solute binding.
• Solute binding to membranes is a bulk phase property, determined by the created interface rather than specific ligand structures.