Biomembrane lipids as components of chromatographic phases: Comparative chromatography on coated and bonded phases

Abstract

SummaryPreparation of biomembrane lipid based stationary phases has been achieved by recycling 1 mM solutions of the appropriate lipid (soybean lecithin phosphatidylcholine, SLPC; phosphatidylcholine, sphingomyelin, phosphatidylethanolamine or phosphatidylserine) in methanol:water (80:20 v/v) through reversed-phase (C8) HPLC columns for 18 hours at 0.25 mL min 1.The chromatographic characteristics (retention, peak symmetry and reproducibilily and phase stabilily) have been assessed and compared with f,,vo commercially available bonded Immobilized Artificial Membrane (IAM) phases (IAM.PC.MG and IAM.PC.DD) by examination of the retention properties of a range of structurally diverse analytes (n = 119). The application of the SLPC phase for prediction of analyte hpophilicily (log Poctanol/water) is shown to be comparable to the IAM.PC.MG and superior to the IAM.PC.DD bonded phases. Cross-phase comparison of analyte retention characteristics on four different lipid phases indicate that such phases may provide a rapid evaluation of analyte-lipid interactions. The dynamic coating methodology is economically viable for the small laboratory, rapid and reproducible, resulting in phase surfaces which are stable over longer periods of time than those of the commercially available bonded phases.

Immobilized Artificial Membrane Chromatography: Quantitative Structure-Retention Relationships of Structurally Diverse Drugs

“…It is important to note that these results are in agreement with the findings by other authors 25,26 who have noted that when carboxylic compounds are treated separately to basic and neutral compounds, improved relationships between log k IAM and log P (octanol/water) are observed. In view of this, it seems reasonable to consider a common interaction mechanism between the carboxylic compounds and the phospholipids of the IAM stationary phases.…”

Lipophilicity and Its Relationship with Passive Drug Permeation

“…Furthermore, mobile phases containing more than 30% acetonitrile (w/w) must be avoided because their microheterogeneity disrupts the structure of water (88). It was reported that IAM stationary phases deteriorate after 3 months of use (89); thus, measures should be taken to check the decrease in capacity factor over time.…”

Hybrid-Supported Bilayers Formed with Mixed-Charge Surfactants on C18-Functionalized Silica Surfaces

“…Raman spectroscopy and differential scanning calorimetry show that the surfactant bilayer also undergoes a broad melting transition, similar in width to that of a hybrid lipid bilayer on the same surface, which is further evidence of their similar interdigitated structure. The observed differences in chain density, organization, and melting transitions between hybrid surfactant and hybrid lipid bilayers are detectable but relatively small, suggesting that hybrid mixed-charge surfactant bilayers might be used in place of hybrid lipid bilayers as a model interface to separate small molecules on the basis of their association with lipid-bilayer-like surfaces. − Charged surfactants are inexpensive reagents, produced on commodity scale, and are available with a variety of head-group functionalities and chain lengths that could be used to tailor the interfacial properties of a hybrid surfactant bilayer surface. On the basis of their biological origins and function, lipid bilayers exhibit unique protein-repellency compared to many other materials; as a result, supported lipid bilayers have been shown to be successful supports for ligands in protein biosensing due to their modest nonspecific adsorption of proteins from solution. − Surfactant-based hybrid-supported bilayers may also exhibit protein-repellent characteristics similar to those of supported lipid bilayers that could prove useful in similar applications.…”

“…These lipid monolayers are employed widely as models for investigating membrane structure and membrane interactions with other molecules. − Phospholipids also accumulate at the boundary between water and solid hydrophobic surfaces that are formed by attachment of n -alkyl chains to a solid support. These stable structures have been termed hybrid-supported lipid bilayers (HSLBs), where the upper leaflet of the bilayer is a phospholipid monolayer and the “lower leaflet” is an immobilized n -alkane layer, originally an n -alkanethiol monolayer assembled on gold or silver substrates. , These hybrid lipid bilayers have been the subject of a variety of studies of their structure − and their interactions with biological molecules. − Similar hybrid lipid bilayers have been formed in n -alkane-modified (C 8 and C 18 ) porous silica and employed as chromatographic stationary phases, − where retention of both small molecules and membrane-active peptides on these model bilayers were found to be comparable to their affinities for phospholipid vesicle membranes. Recent confocal Raman microscopy studies of HSLBs on C 18 -modified silica surfaces determined that acyl chains of the lipid in the hybrid bilayer are interdigitated with the n -alkyl chains bound to the silica surface .…”