Membrane Partition Coefficients Chromatographically Measured Using Immobilized Artificial Membrane Surfaces

Abstract

Immobilized artificial membranes (IAMs) are chromatographic surfaces prepared by covalently immobilizing cell membrane phospholipids. IAM surfaces mimic fluid cell membranes. Solute capacity factors (k'IAM) measured on IAM columns correlate very well with solute equilibrium partition coefficients (Km') measured in fluid liposome systems. For 23 structurally unrelated compounds, log-(k'IAM) correlates with log(Km') with a linear correlation coefficient r = 0.907. This indicates that solute partitioning between the IAM bonded phase and the aqueous mobile phase is similar to the solute partitioning between liposomes and the aqueous phase. Although both IAM chromatography and liposome partitioning can be used as in vitro methods to predict solute partitioning into cell membranes, IAM chromatography is experimentally convenient compared to liposome systems. To study the effect of lipid structure on drug binding to IAMs, IAMs were prepared from three different phosphatidylcholine ligands: (i) a diacylated phosphatidylcholine ligand, (ii) a single chain ether phosphatidylcholine ligand, and (iii) a single chain phosphatidylcholine ligand that lacks a glycerol backbone. Solute retention data were identical for all of these IAMs, and consequently, predictions of solute binding to fluid membranes were also identical. This indicates that the structure of the phosphatidylcholine ligand that is immobilized is not critical for the binding of solutes. Since the structure is not important, the binding of solutes to membranes is a bulk phase property, i.e., it is the interface created by the ligands that determines the solute binding properties, not the ligands themselves. Solute partitioning using octanol/water systems does not correlate with k'IAM unless a homologous series of hydrophobic solutes is being evaluated.

Drug-Membrane Interactions Studied in Phospholipid Monolayers Adsorbed on Nonporous Alkylated Microspheres

“…The retention factors were used as descriptors for prediction of the trans-bilayer transport of chemicals. [35][36][37][38] The liposome and IAM binding were correlated for some compounds 39 and not correlated for other compounds. 40 A systematically higher partitioning to IAMs than to liposomes was measured for several other series of compounds.…”

Blood-Brain Barrier Permeation: Molecular Parameters Governing Passive Diffusion

“…Interesting modifications of this approach are HPLC methods where alkyl chains (e.g., C-18) (Kaliszan, 1990), or carboxyacyl phosphocholine chains (e.g., 11-carboxylundecylphosphocholine) (Ong et al, 1995;Yang et al, 1997) are covalently attached to silica. These systems show a limited anisotropy.…”

Cellular membrane affinity chromatography (CMAC) in drug discovery from complex natural matrices

“…This study stimulated Wainer's group to approach the immobilization process of nicotinic acetylcholine receptors (nAChRs) on lipid monolayers [13]. Interestingly α 3 β 4 nAChRs were also successfully immobilized on the immobilized artificial membrane (IAM) stationary phase, developed by Pidgeon et al [14] and currently available from Regis Technologies, Figure 2. Studies by the Wainer group showed that CMAC prepared with the use of IAM particles were characterized by better reproducibility compared to liposomal columns [13].…”