EFFECTS OF TEMPERATURE AND MOBILE PHASE COMPOSITION ON THE INTERACTION BETWEEN BERBERINE AND IMMOBILIZED β₂-ADRENOCEPTOR BY HIGH PERFORMANCE AFFINITY CHROMATOGRAPHY

Abstract

Self-competitive displacement is used to examine changes in the association constant and the binding site for berberine binding to immobilized β₂-adrenoceptor (β₂-AR) at different temperatures and using a varying mobile phase. The compound was confirmed to have a single kind of binding site to β₂-AR under all the tested conditions. At 298.15 K, the association constant and the binding site are (2.12 ± 0.02) × 10⁴ M⁻¹ and (1.56 ± 0.02) × 10² M. Thermodynamic investigation indicates that the binding of berberine to β₂-AR has a positive change in energy due to enthalpy and negative response to entropy changes. Accordingly, this interaction is thought to be an endothermal process with entropy increase. The binding of berberine to the receptor was found to be more sensitive to ionic strength than pH. The placing of 1-propanol up to 5.0% in the mobile phases generates an 18% decrease in retention for berberine. These results indicate that the immobilized receptor would probably be an alternative for exploring the binding mechanism of ligand and receptor.

Keywords:

• β₂-adrenoceptor
• affinity chromatography
• association constant
• berberine
• binding site
• immobilized receptor

ACKNOWLEDGMENT

Financial support is kindly provided from the National Natural Sciences Foundation of China (No. 21005060), the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT1174), the Chinese Ministry of Education (No. 20106101110001), the Technology Support Plan Project (No. 2008BAI51B01), and the Department of Education of Shaanxi Province (No. 11JK0661).

Notes

All the experiments were performed at 25°C.