Identification and Analysis of Stereoselective Drug Interactions with Low Density Lipoprotein by High-performance Affinity Chromatography

Authors

Matt Sobansky, University of Nebraska - Lincoln
David S. Hage, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

4-2012

Citation

Anal Bioanal Chem. 2012 April ; 403(2): 563–571. doi:10.1007/s00216-012-5816-y.

Comments

Copyright 2012 Springer Verlag. Used by permission.

Abstract

Columns containing immobilized low density lipoprotein (LDL) were prepared for the analysis of drug interactions with this agent by high-performance affinity chromatography (HPAC). R/SPropranolol was used as a model drug for this study. The LDL columns gave reproducible binding to propranolol over 60 h of continuous use in the presence of pH 7.4, 0.067 M potassium phosphate buffer. Experiments conducted with this type of column through frontal analysis indicated that two types of interactions were occurring between R-propranolol and LDL, while only a single type of interaction was observed between S-propranolol and LDL. The first type of interaction, which was seen for both enantiomers, involved non-saturable binding; this interaction had an overall affinity (nK_a) of 1.9 (± 0.1) × 10⁵ M^-1 for R-propranolol and 2.7 (± 0.2) × 105 M-1 for S-propranolol at 37 °C. The second type of interaction was observed only for R-propranolol and involved saturable binding that had an association equilibrium constant (K_a) of 5.2 (± 2.3) × 10⁵ M^-1 at 37 °C. Similar differences in binding behavior were found for the two enantiomers at 20 °C and 27 °C. This is the first known example of stereoselective binding of drugs by LDL or other lipoproteins. This work also illustrates the ability of HPAC to be used as a tool for characterizing mixed-mode interactions that involve LDL and related binding agents.