Fluorescence Spectroscopic Study of Interaction between Olanzapine and Bovine Serum Albumin

Abstract

The binding capacity of an antipsychotic drug, olanzapine with bovine serum albumin (BSA) was studied. The experiment was designed to investigate the interaction between olanzapine and BSA using fluorescence spectroscopy at different temperatures (298 K and 308 K). Fluorescence quenching constant was determined from Stern-Volmer equation. Van't Hoff equation was used to determine the thermodynamic parameters such as free energy (ΔG), enthalpy (ΔH) and entropy (ΔS). A strong quenching was observed in the fluorescence spectrum. The quantitative analysis revealed that olanzapine bound with BSA via a dynamic quenching through hydrophobic interactions, where binding constant K b at 280 nm was 10.28x10 4 μM-1 and 10.739x10 4 μM-1 at 298 and 308 K, whereas it was 19.31x10 4 μM-1 and 18.923x10 4 μM-1 when the study was conducted at 293 nm, respectively. The number of bound olanzapine molecules per BSA protein was ~0.5 at both the temperatures. The K b value in different temperatures suggested that the stability of BSA-olanzapine complex increased with the increase of temperature at 280 nm but reversed effect was observed in excitation wavelength of 293 nm. Positive ΔH o and ΔS o were the distinctive characteristics that allowed us to suggest that the interaction was mostly hydrophobic in nature.